Is greenness surrounding schools and kindergartens associated with symptoms of attention-deficit/hyperactivity disorder among children?In this large cross-sectional study of 59 754 Chinese children, attendance at schools or kindergartens in greener areas was associated with lower odds of having attention-deficit/hyperactivity disorder symptoms.These findings may be useful for policy makers and health care professionals to develop strategies  to mitigate the attention-deficit/hyperactivity disorder burden. This cross-sectional study evaluates the association between greenness surrounding schools or kindergartens and symptoms of attention-deficit/hyperactivity disorder among Chinese children. Few studies have investigated the association between greenness and childhood attention-deficit/hyperactivity disorder (ADHD).To evaluate the association between greenness surrounding schools or kindergartens and symptoms of ADHD in children.This population-based cross-sectional study was performed between April 2012 and January 2013 in 7 cities in northeastern China. This analysis included 59 754 children (aged 2-17 years) from 94 schools and kindergartens, who had resided in the study area for 2 years or longer. Data were analyzed from April 15, 2019, to October 10, 2019.Greenness surrounding each child’s school or kindergarten was estimated using 2 satellite image–derived vegetation indexes: the normalized difference vegetation index and the soil-adjusted vegetation index.Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) scales were used to measure ADHD symptoms (9 inattention symptoms and 9 hyperactivity-impulsivity symptoms). Parents or guardians rated the frequency of each of 18 ADHD symptoms during the preceding 6 months. Children with 6 or more symptoms of either inattention or hyperactivity-impulsivity were defined as having ADHD symptoms. Generalized linear mixed models were applied to estimate the association between greenness and ADHD symptoms.P < .001 for both). The associations were robust in a series of sensitivity analyses.The mean (SD) age of the 59 754 study participants was 10.3 (3.6) years, and 29 494 (49.4%) were girls. A total of 2566 participants (4.3%) had ADHD symptoms. Greenness levels differed substantially across schools and kindergartens. The normalized difference vegetation index within 500 m of a school or kindergarten ranged from −0.09 to 0.77. Greater greenness levels were associated with lower odds of ADHD symptoms. In covariate-adjusted models, a 0.1-unit increase in normalized difference vegetation index or soil-adjusted vegetation index within 500 m of a school or kindergarten was significantly associated with lower odds of ADHD symptoms (odds ratios, 0.87  and 0.80 , respectively; These findings suggest that there may be a beneficial association between school-based greenness and ADHD symptoms in Chinese children. Future longitudinal and mechanistic studies are needed to confirm the findings of this cross-sectional analysis and further explore potential mechanisms of this association. In a recent meta-analysis2 of 67 Chinese studies of children, the prevalence of ADHD reached 6.3%. Prior evidence suggests that ADHD has a range of negative outcomes on individuals, as well as economic burdens on families and society.4 Because environmental factors are associated with ADHD,5 identifying such factors may be useful for reducing ADHD symptoms, especially considering that environmental factors are generally modifiable.Attention-deficit/hyperactivity disorder (ADHD) is among the most common neurobehavioral conditions in childhood. Globally, approximately 7.2% of children are estimated to have ADHD.6 The underlying mechanisms include reducing harmful exposures, such as air pollution and noise, encouraging physical activity, mitigating mental stress, and enriching microbial diversity.6 Several previous epidemiological studies14 investigated the association between greenness and ADHD (or ADHD symptoms) in all children and with ADHD severity in children with a diagnosis of ADHD, but the results were inconsistent  reporting guideline for cross-sectional studies. All participants’ parents or guardians gave written informed consent. The Human Studies Ethics Committee of Sun Yat-Sen University reviewed and approved the study protocol. This study follows the Strengthening the Reporting of Observational Studies in Epidemiology  (DSM-IV) ADHD scales to measure ADHD symptoms.15 Participants’ parents or guardians completed the ADHD DSM-IV survey, which includes 9 inattention symptoms and 9 hyperactivity-impulsivity symptoms. Respondents rated the frequency of each ADHD symptoms in the preceding 6 months on a 4-point scale: never or rare, 0; sometimes, 1; often, 2; or very often, 3. We used the Chinese version of the DSM-IV ADHD scale, which has been demonstrated to be valid and reliable for the Chinese population.16 Consistent with DSM-IV criteria, children presenting with 6 or more symptoms of either inattention or hyperactivity-impulsivity were defined as having ADHD symptoms. The symptoms of ADHD can be classified into 3 subtypes: predominantly inattention, predominantly hyperactivity-impulsivity, and both inattention and hyperactivity-impulsivity.We used 17 The C-ASQ measures ADHD symptoms on a 4-point scale: never or rare, 0; sometimes, 1; often, 2; or very often, 3. The C-ASQ scores for ADHD symptoms thus range from 0 to 30, and a score greater than 15 was defined as the presence of ADHD symptoms.17 The C-ASQ is derived from the Revised Conners Parent Rating Scale and has been translated and validated for use in Chinese population.18To assess the robustness of our outcome assessment strategy, we also used the 10-item Conners Abbreviated Symptom Questionnaire (C-ASQ) to identify ADHD symptoms.19 and the soil-adjusted vegetation index (SAVI).20 Both indices were derived from Landsat 5 Thematic Mapper satellite images obtained at a resolution of 30 m × 30 m. The derivation of NDVI is based on land surface reflectance of visible (red) and near-infrared parts of the spectrum, and SAVI also incorporates a correction factor to minimize the impact of soil background. Both NDVI and SAVI values range from −1 to 1, and although values do not map to specific types of land cover, higher values represent more greenness , negative values represent water bodies, and values close to 0 generally correspond to barren areas . We downloaded 2 cloud-free satellite images taken in August 2010, the greenest month in northeastern China and the time closest to health data collection. School and kindergarten greenness was estimated as the mean NDVI and SAVI values in buffers of 100 m, 500 m, and 1000 m around the centroid of each school or kindergarten. Both NDVI and SAVI were calculated using ArcGIS visualization software version 10.4 (ESRI).We assessed greenness surrounding schools and kindergartens by 2 vegetation indices: the normalized difference vegetation index (NDVI)21 The following variables were retained as confounders in multivariable regression models: children’s age,23 children’s sex,25 parental education level,27 household income level,27 type of home district,27 and dog ownership.28We used a questionnaire to collect data on the following variables: children’s age (years), children’s sex , parental education level , annual household income level , type of home district , dog ownership (yes or no), cigarette smoking during pregnancy (yes vs no), alcohol drinking during pregnancy (yes vs no), breastfeeding , preterm birth (yes [defined as <37 weeks’ gestation] vs no [defined ≥37 weeks’ gestation]), number of siblings (0 vs ≥1), and birth weight (grams). Then, we developed a directed acyclic graph  and 95% CIs per 0.1-unit greater NDVI and SAVI were estimated. Because of the generalized linear mixed models framework, the ORs are school or kindergarten specific and not population averaged. We estimated crude models, unadjusted regression models, and regression models adjusted for covariates selected using the directed acyclic graph  and SAVI for 500 m (SAVI500-m) into quartiles to check for nonlinear associations. We split ADHD into subtypes  to compare the association of greenness with different subsymptoms of ADHD to assess specificity of the associations, and we also redefined ADHD using the C-ASQ to assess the effect of outcome misclassification. We generated regression models with additional adjustment for maternal smoking during pregnancy,29 maternal alcohol consumption during pregnancy,30 breastfeeding,31 preterm birth,32 birth weight,33 and number of siblings34 to assess those associations with ADHD symptoms. Finally, we excluded children with allergic diseases ,35 congenital heart diseases,36 preterm birth,32 or low birth weight (defined as birth weight <2500 g)33 as a group potentially with greater baseline risk for ADHD.We performed several sensitivity analyses to evaluate the robustness of the results in our main effects models. First, we estimated NDVI and SAVI in buffers of 100 and 1000 m to assess the impact of exposure misclassification. We also categorized NDVI for 500 m . A 2-tailed P < .05 denoted statistical significance.Data were analyzed from April 15, 2019, to October 10, 2019. All statistical analyses, including χA total of 68 647 children’s parents or guardians were invited to participate. Of those, 63 910 completed and returned a study questionnaire . We then excluded 4156 children who resided at their current address for less than 2 years. Finally, 59 754 children were included in this analysis.Of the 59 754 children included in the analysis, 2566 (4.3%) had ADHD symptoms . The mea500-m values ranged from −0.09 to 0.77). The NDVI and SAVI values were positively correlated with each other   than those without ADHD symptoms   . Of note500-m and SAVI500-m, OR, 0.81  and 0.72 , respectively; P < .001 for both) .In unadjusted models, we observed that higher greenness exposure was significantly associated with lower odds of ADHD symptoms  . The assP < .001 for all)  . In addi500-m, OR, 0.85 ; per 0.1-unit greater SAVI500-m, OR, 0.78 ) than among children aged 2 to 6 years , and among children living in residential areas  than those living in business or industrial areas . However, neither interaction was statistically significant; thus, the results should be interpreted with caution. Also, no significant association was observed for sex, household income, or dog ownership.In this large cross-sectional study of Chinese children, we investigated the association between greenness surrounding schools or kindergartens and ADHD symptoms and observed that children studying in greener schools or kindergartens had lower odds of having ADHD symptoms. To our knowledge, this is the first study to evaluate greenness and ADHD symptoms in a developing country. This is also one of the few studies focused on the health outcomes of school-based greenness, where children usually spend most of their daytime.10 evaluating the association of ADHD symptoms with school greenness. In that study from Barcelona, Spain, the authors recruited 2111 children aged 7 to 10 years, measured ADHD symptoms using DSM-IV score, and assessed school-based greenness using NDVI. They observed that higher NDVI levels were not significantly associated with fewer ADHD symptoms. Our study had several similarities in design, exposure, and outcome assessment, as well as participants’ age. However, the sample size and number of schools in our study were approximately 28- and 3-fold larger than those in the earlier study. Thus, our study had greater statistical power to detect modest associations, and our estimates may be more precise.We are aware of only 1 previous cross-sectional study10 detected beneficial associations between residential greenness and ADHD symptoms in Spanish children. Similarly, a cross-sectional study14 of 1717 Korean children found that residential greenness was significantly associated with a lower ADHD score. In a cohort study13 of 66 823 German children, it was reported that higher greenness levels in large postal areas were associated with lower risk of ADHD incidence. Two observational studies from Germany11 and Lithuania12 reported that greater proximity to city parks, but not residential greenness, was associated with fewer ADHD symptoms. Additionally, 1 single-blind controlled trial8 and 1 cross-sectional study9 found that walking or playing in green settings might decrease the severity of ADHD. Although the results of previously published studies and ours are not identical, the collective evidence generally supports a beneficial association between higher greenness levels and reduced ADHD or ADHD symptoms.Although studies focusing on school-based estimates of greenness are scarce, several have investigated the associations of other greenness indicators with ADHD symptoms. For instance, Amoly et al37 and, thus, contact with the natural world is postulated to be beneficial for children’s brain development and attention restoration.38 A recent study39 of Barcelona schoolchildren provided strong evidence for this hypothesis by evaluating associations between long-term exposure to residential greenness and regional differences in brain volume. They found that greenness exposure was associated with improvements in brain regions associated with better working memory and attentiveness. Higher levels of ambient air pollution have been adversely associated with neurodevelopment as well as ADHD symptoms,41 and green space has been suggested to reduce levels of air pollutants.6 Similarly, exposure to higher ambient noise levels increased ADHD symptoms in children.42 The ability of greenness to reduce noise43 may, therefore, partially explain the beneficial association between greenness and ADHD symptoms in our study. Populations living in greener areas tend to engage in physical activity more frequently,6 and sufficient physical activity may improve cognitive development and reduce ADHD symptoms.44 Furthermore, failing immunoregulation associated with reduced exposure to macroorganisms and microorganisms is thought to have adverse outcomes on brain development, whereas greenness has the ability to enrich immunoregulation-inducing microbial input from the environment.45 This might be another pathway driving our observed association between greenness and ADHD symptoms.Several mechanisms might explain the association between greenness and ADHD. The biophilia hypothesis suggests that human beings are innately attracted to nature,1 Attention-deficit/hyperactivity disorder impairs many areas of children’s lives, including social functioning, academic performance, and overall quality of life, which ultimately lead to major health, social, and economic burdens.4 Intervention strategies are, therefore, needed to address this pandemic. Our results suggest that attending schools or kindergartens with higher levels of surrounding greenness is associated with lower odds of ADHD symptoms. Given that attention is a critical prerequisite for learning, greenness in school settings may be of great public health significance. Our findings, therefore, are relevant to policy makers and health care authorities for translating evidence into feasible and achievable targeted interventions  to mitigate the burden of ADHD in children.As one of the most common neurobehavioral conditions in childhood, ADHD affects approximately 7.2% of youth worldwide and the rate is still increasing in some populations.This study has several strengths. First, it includes a large population-based sample, covering 94 schools and kindergartens in 7 Chinese cities. Second, China’s school policy restricts student admission according to geographical boundaries, which prevents students from attending transregional schools. In this study, the distance between school and home was short ; thus, the school-based greenness in larger buffer exposures may also capture children’s greenness exposure near home, and this was further supported by our findings that associations were greater for larger buffers of greenness metrics. Third, we incorporated a set of individual-, family-, and neighborhood-level covariates into the models to control for potential confounding. Fourth, we used 2 exposure metrics and 3 different buffers for green space, as well as 2 different instruments, for assessing ADHD symptoms. In addition, we performed a series of sensitivity analyses to demonstrate that our results were robust.46 Thus, effect estimates may have been greater if we had captured individual exposures. Third, we used satellite image–based NDVI and SAVI to assess greenness exposure; these indices provide information on the general level of vegetation but cannot distinguish between structure, type, and quality of greenness. This prevents us from identifying the specific aspects of green space most closely associated with ADHD symptoms. Fourth, information on covariates and outcomes was collected using questionnaires; thus, a recall bias is possible. Fifth, although we have controlled for a rich set of confounding covariates, several important covariates were still unavailable . Thus, the potential for unmeasured confounding is possible. Sixth, ADHD symptoms were measured using questionnaires completed only by parents and guardians and were not clinically verified. In addition, we did not ask whether the children had received a diagnosis of ADHD or were receiving medication. Furthermore, the DSM-IV criteria are intended for children aged 6 years or older, but we included children aged 2 to 6 years. Thus, we may have misclassified some children, although we used 2 different validated instruments (DSM-IV and C-ASQ) to detect ADHD symptoms and found that the results were consistent.This study also has some limitations. First, the cross-sectional design did not allow us to identify a temporal sequence between greenness and ADHD symptoms. However, the possibility of reverse causality—that is, the possibility that children with ADHD symptoms may choose a school with less green spaces—is low. Second, we did not have access to personal addresses, but rather school or kindergarten addresses, which means that we only had 94 unique exposure data points for the 59 754 participants. This method might have introduced exposure misclassification. However, the misclassification was likely nondifferential, which often, but not always, biases the results toward null.This study suggests that greater levels of greenness near schools or kindergartens are associated with lower odds of ADHD symptoms in Chinese children. Our results may be useful for policy makers and health care professionals for developing strategies to mitigate the ADHD burden in China. Well-designed longitudinal epidemiological studies and mechanistic studies are warranted in the future.


ADHD risk increased with the number of aforementioned biochemical risk factors present . Findings suggest that either ADHD’s etiology is multidimensional or the aforementioned conditions have shared etiology with ADHD.This study investigated whether common comorbidities or biochemical factors, such as allergic disease, anemia, inflammation, and neurotransmitters, are singly or additively associated with an increased risk of attention deficit–hyperactivity disorder (ADHD). We recruited 216 children diagnosed with ADHD and 216 age-, sex-, height-, weight-, and class-matched controls from 31 elementary schools in Taipei, Taiwan. The International Study of Asthma and Allergies in Childhood questionnaire was used to measure allergic symptoms. Fasting venous blood was collected and analyzed for complete blood count, white blood cell differential count, immunoglobulin (Ig) E level, and serotonin (5-HT) level. The results showed that symptoms of both rhinitis  and eczema  were significantly associated with increased risk of ADHD. Children with ADHD showed considerably lower levels of hemoglobin ( ADHD may have a substantial influence on children’s school performance, familial relationships, and social interactions3. Thorough investigation of ADHD’s complex etiology is vital for improving its diagnosis, prevention, and management4. ADHD is associated with various comorbidities, including allergic disease, immune dysregulation, neurotransmitter underproduction, anemia, and oxidative and endocrinological imbalances6.Attention deficit–hyperactivity disorder (ADHD), one of the most frequent neuropsychiatric disorders found in children, is characterized by a lack of impulse control, inattention, and hyperactivity11. Immune responses resulting from these allergic diseases may affect the central nervous system (CNS) and predispose children with neurodevelopmental disorders, including ADHD12. Therefore, evaluating ADHD symptoms in children and adolescents with allergic diseases may facilitate ADHD identification9. Furthermore, identifying allergic diseases in children exhibiting ADHD symptoms provides an opportunity to control allergies. A recent randomized small-scale, placebo-controlled trial showed that rhinitis control combined with Ritalin administration can effectively alleviate ADHD endpoints13. Allergies result from immune responses that often involve chronic inflammation14. Immunoglobulin (Ig) E is an antibody found only in mammals, and an elevated IgE level is usually related to atopic diseases15. IgE-mediated allergic and inflammatory pathways are targets for intervention in the pathological processes of allergic diseases16. Furthermore, eosinophils, one of the five major leukocyte types, are responsible for tissue damage and inflammation in allergic diseases. However, little is known about whether the markers of allergy  may be linked to ADHD.Regarding the neurophysiological mechanisms, various allergic diseases, including allergic rhinitis, atopic dermatitis, and asthma, have already been associated with ADHD17. The most prevalent form of anemia is iron deficiency anemia. Low levels of serum ferritin, a biomarker of iron store, are correlated with risks of cognitive deficits and behavioral and psychiatric problems in pediatric populations18. A large-scale field study demonstrated that a lower ferritin level may be associated with parent-reported hyperactivity after controlling for confounding factors19. Furthermore, research, including a Taiwanese study, has indicated that iron deficiency or iron deficiency anemia may be a potential risk factor for neurodevelopmental disorders including ADHD21. Iron deficiency may also reduce the effectiveness of psychostimulant treatment in children with ADHD22. A routine complete blood count (CBC) can detect anemia, a late-stage marker of iron deficiency. This low-cost method may indicate poor iron nutrition and unsatisfactory response to psychostimulant treatment to prompt clinicians to treat these children with ADHD.Atopic diseases, such as eczema, asthma, hay fever, and food allergies, are associated with anemia5-HTTLPR) can influence impulsivity in humans24. In addition, 5-HT can modulate several immunological events, such as activation, proliferation, cytokine secretion, and chemotaxis of leukocytes. The influence of 5-HT on immune cells may be associated with the pathologies of inflammatory diseases25 or atopic diseases 27. Therefore, 5-HT deficits have been indicated as participating in the etiology of ADHD28. However, findings related to 5-HT circulation levels in ADHD patients have been inconsistent among previous case–control studies, with some studies indicating that children with ADHD tend to have lower blood levels of 5-HT31. However, other studies have not found this difference33. Therefore, additional studies with larger sample sizes  are required to confirm the association between 5-HT and ADHD.Serotonin (5-HT) is a monoamine neurotransmitter that induces metabolic effects in a variety of cell types both in the CNS and peripheral nervous system. A polymorphism on the 5-HT transporter gene  between the number of risk factors and susceptibility to ADHD. If links between the aforementioned risk factors and ADHD are established, routinely screening these underlying pathophysiological indicators may be helpful for devising a comprehensive treatment strategy for ADHD. Therefore, we conducted a case–control study by strictly matching age, sex, height, weight, and class to investigate whether ADHD is correlated with the aforementioned factors.This study received approval from the Medical Research Ethical Committee of the Institute of Biomedical Sciences at Academia Sinica (AS-IBMS-MREC-92-01). All procedures involving participants were in accordance with the ethical standards of the institutional and national research committees and the Helsinki Declaration.34. Of all screened students, 287 students scored higher than the 85th-percentile values on both scales and were referred for further clinical evaluation. After being interviewed by a child psychiatrist on our research team, 252 students were diagnosed with ADHD according to the criteria of the Diagnostic and Statistical Manual, Fourth Edition, Text Revision (DSM-IV-TR). Control students were randomly selected from the same classes as the ADHD students were and matched by age, sex, height, and body weight (within a 5% range). After students with incomplete data were excluded, this analysis comprised 216 children with ADHD and 216 controls.We mailed invitation letters to elementary schools in the Taipei metropolitan area and visited the schools agreeing to participate. Teachers distributed informed consent forms (ICFs). After completed ICFs were received from parents, we screened the students aged 8–10 years for potential ADHD on two validated scales: the Chinese version of the Conners Teacher Rating Scale (for teachers) and the Chinese version of the Werry–Weiss–Peters Activity Scale (for parents)35, and symptoms of asthma, rhinitis, and eczema were identified.We obtained information on family education levels, family income, lifestyle, and disease history of students and their parents through a questionnaire. Body weights and heights of the participating children were measured by trained technicians. We had parents fill out the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaireApproximately 10 mL of fasting venous blood was drawn from each child and stored in darkness throughout the biospecimen handling process. CBC analysis was performed at each school using EDTA-blood with a blood autoanalyzer . All serum and plasma samples were kept at −70 °C until analysis. We measured routine blood clinical chemistry and plasma C-reactive protein (CRP) concentrations by using the Olympus AU 600 Autoanalyzer . IgE levels in the serum were analyzed with the radioimmunosorbent test and capsulated hydrophilic carrier (CAP) method . Finally, we obtained histamine levels (CV: 2.2–9.2%) and 5-HT levels (CV: 3.6–17.9%) using ELISA kits .t test for continuous variables. Logistic regression models were used to determine the relationships between each allergic disease (yes or no) and ADHD (present or absent). Eosinophil count and histamine, CRP, IgE, and 5-HT levels demonstrated a significant level of positive skewness. We applied arithmetic logarithmic transformations to approximate normal distributions for the aforementioned variables before preforming further statistical analyses. A p of < 0.05 was considered statistically significant. Bonferroni correction was applied to adjust for multiple testing in the group comparison, with regard to multiple biochemical indices (p = 0.05/16 = 0.003125).All statistical analyses were conducted using SAS . We performed group comparisons between cases and controls using the chi-square test for categorical variables and Four indicators were identified: hemoglobin (Hb), eosinophil, IgE, and serotonin (5-HT). Risk conditions were defined by low levels of Hb and 5-HT, but high eosinophil count and IgE levels. Because no sex differences in these risk factors were noted among the children, we classified students into quartiles for each of the risk factors to compare effect sizes. We used logistic regression to determine the odds ratios of biochemical risk conditions as well as allergic conditions for their influences on ADHD. Potential confounders—namely jaundice after birth, mother with smoking habit, expenditure balanced with revenue, facing stressful situation (see Table (Table ). Children with ADHD were more likely to have parents with lower education levels, blue-collar jobs, unstable incomes, higher levels of familial stress, conditions such as hypoxia or jaundice during or after delivery, and siblings with ADHD. Furthermore, children with ADHD tended to have mothers who were current smokers, smoked during pregnancy, and had experienced miscarriage symptoms in their first trimester of pregnancy.Because children with ADHD and control children were matched by age, height, weight, body mass index, grade level, and sex, the distributions and means of these variables were comparable Table . ChildreAccording to the ISAAC questionnaire, 24.5%, 61.6%, and 20.4% of our students with ADHD had symptoms of asthma, rhinitis, and eczema, respectively  range, logistic regression models indicated that Hb < 12.6 g/dL, 5-HT < 113.57 ng/mL, IgE > 367 KU/L, and eosinophil >5.85% were all significantly associated with an increased ADHD risk Table . FurtherTo our knowledge, this study is the first to examine the relationship between ADHD and allergies along with multiple biochemical indices related to immune-mediated inflammation. Compared with control participants, children with ADHD had higher prevalence of allergic diseases, higher eosinophil counts, higher IgE levels, lower blood 5-HT concentration, and lower Hb levels. The higher the number more risk factors was, the higher the odds of being diagnosed with ADHD were. This finding suggests the coexistence of ADHD and several clinical conditions, including allergic diseases; biomarkers of immunological responses and the associated conditions, such as anemia; and lower 5-HT levels.36. Furthermore, our study showed the number of allergic disease symptoms had a dose–response effect on ADHD, suggesting that patients with ADHD had more allergic conditions than their counterparts without ADHD. Various reasonable biological mechanisms linking ADHD and allergies were proposed37. Allergic reactions result in an increase in inflammatory cytokines from TH2 or TH17 cells38, which may stimulate the neuroimmune mechanism in the brain circuits, such as the prefrontal cortex and the anterior cingulate cortex, associated with emotional and behavior control40. ADHD symptoms resemble cognitive disturbances caused by functional and structural changes in the aforementioned two brain circuits. Although neither the existing literature nor this study could provide a chronological sequence from the development of atopic disease to that of ADHD, we found total IgE levels and percentage of eosinophils to be elevated in children suffering from ADHD. Because it is unlikely that ADHD causes allergy, these findings support the hypothesis that allergies precede or coexist with ADHD because of some shared etiology. Although it is not confirmed at the present time whether or how allergy is involved in the etiology of ADHD, allergic symptom assessment may be considered in the comprehensive appraisal and management of ADHD in children.The results of our study indicate a significantly higher prevalence of rhinitis and eczema in the ADHD group than in the control group. This finding is consistent with that of a previous meta-analysis on allergic diseases and ADHD, although only eczema was independently related to ADHD in that study41. Previous studies have also found iron deficiency to alter dopamine transporter function in rat striatum42. Not only is iron involved in neurotransmitter production but iron deficiency may also contribute to the development of ADHD by disrupting the oxygen supply to the brain43 and disturbing growth and cognitive ability44. Studies related to the iron status of patients with ADHD and controls have been controversial46. We did not directly assess ferritin levels, but rather performed a routine CBC assessment. We observed significantly lower Hb levels in children with ADHD. Although the threshold points for Hb (12.6 g/dL at 25th-percentile) did not reach the criterion for anemia, this finding indicates that subclinical anemia may be associated with certain aspects of ADHD. Iron deficiency is the only possible cause of microcytic anemia. The lower Hb levels in children with ADHD may have also resulted from other nutrient deficiencies, such as folate, vitamin B6 or B12, or other inflammatory or parasitic conditions. Moreover, asthma and infectious diseases have also been associated with anemia48, implying that allergies (immune responses) and anemia may share a biological process and environmental factors. Determining causes of anemia is not difficult clinically and may help to improve the overall well-being of patients with ADHD.Iron deficiency may also result in an insufficient supply of neurotransmitters because iron is a cofactor of tyrosine hydroxylase and tryptophan hydroxylase49. We found that children with ADHD had lower 5-HT levels compared with healthy controls. This finding agrees with those of previous studies31 but disagrees with those of others33. Relative to previous studies that investigated a similar topic, the current study featured a larger sample and matched controls more strictly. Therefore, we believe that our study possessed greater statistical power compared with previous small-scale studies. Furthermore, a recent study indicated that the peripheral function of the 5-HT metabolic pathway can serve as a significant predictor of aggressive behavior50. It has also been found that 5-HT may also exert effects on immune cells and link to the pathologies of inflammatory diseases25 or atopic diseases (eczema or atopic dermatitis)27. Therefore, certain characteristics of children with ADHD, such as impulsivity, temper tantrums, or aggression, may be partially related to lower peripheral 5-HT levels.The CNS inhibitory neurotransmitter 5-HT correlates with impulse control and emotionsp < 0.05), the discriminative validity of each was not robust. We found that children with more of the aforementioned biochemical risk factors were more likely to be diagnosed with ADHD. The dose–response relationship between the number of risk factors and susceptibility to ADHD supports either the idea that the etiology of ADHD may be multifaceted or that ADHD coexists with allergy, immunological stress, anemia, and low 5-HT levels because of a shared etiology51. Notably, several of these biomarkers may also interact with each other. Studies52 have demonstrated that several nutritional factors and allergic reactions are associated with serotonin levels. Additional studies are required to clarify the underlying mechanisms of the relationships between these biochemical abnormalities and ADHD and assess their predictive values and applicability in clinical settings. Because allergic diseases and low levels of Hb and 5-HT may be modifiable through dietary intervention, nutritional supplements, or medical treatment, clinicians should monitor these factors in children exhibiting ADHD symptoms. Adequate correction for these risk factors may be beneficial to some children diagnosed with ADHD or who respond poorly to ADHD drug therapy (maybe phenocopies of ADHD).Here, although each single factor showed significant differences between the ADHD group and control group  and severity of allergic diseases and biomarkers consequently remain uncertain. Third, allergy symptoms were only defined using the ISAAC. Nonetheless, findings on IgE and eosinophil were consistent with the questionnaire results. In addition, this study only measured Hb concentration in the blood. We cannot confirm whether it is anemia or iron deficiency that is involved in ADHD etiology. Finally, not only 5-HT but also other neurotransmitters  are involved in the pathophysiology of ADHDIn conclusion, ADHD is associated with several comorbidities, including allergic symptoms, subclinical anemia, and low 5-HT levels; furthermore, the number of biochemical risk factors is associated with the presence of ADHD in a dose–response manner. Thus, either ADHD etiology is potentially multidimensional or ADHD has shared etiology with the other included clinical conditions. Future longitudinal studies should investigate the causal relationships between these subclinical indicators and ADHD and determine whether ADHD risk can be modified by appropriately managing allergic symptoms and Hb and neurotransmitter levels.


There is a controversy regarding temporal trends in prevalence of attention-deficit/hyperactivity disorder (ADHD). Using nationwide claims data containing data for approximately six million statutory health insured children we aimed to examine a) trends of ADHD administrative prevalence during 2009–2016; b) regional variations in prevalence, and c) factors associated with an increased chance of ADHD diagnosis. The ICD-10 code ‘F90-hyperkinetic disorder’ was used to define an ADHD case. Global and Local Moran’s I tests were used to examine the spatial autocorrelation and k-means-cluster analysis to examine the course of ADHD prevalence in administrative districts over years. Two-level logistic regression was applied to examine individual- and district-level factors associated with ADHD diagnosis. The administrative prevalence of ADHD was 4.33% (95% CI: 4.31–4.34%). We observed pronounced small-area differences on the district level with prevalences ranging between 1.6% and 9.7%. There was evidence of strong spatial autocorrelation . The k-means-method identified six clusters of different size; all with a stagnating trend in the prevalence over the observation period of eight years. On the district level, a lower proportion of foreign citizens, and a higher density of paediatric psychiatrists and paediatricians were positively associated with ADHD with a more pronounced effect in urban districts. Globally, the reported ADHD prevalence varies between 1% and 7%2. Regional variations within countries were also reported, e.g. in Germany3, the UK4 and the US5. It is argued that regional variations can be explained by sociodemographic factors, health care access or availability of medical specialists3, but evidence from empirical studies is lacking. Second, there is a controversy regarding temporal trends of the disease frequency. A few studies reported about rising trends of disease frequency (reviewed in6). In Germany, an increase in prevalence was reported by two studies7; e.g. from 2.5% in 2005 to 4.2% in 20153 and from 5.0% in 2009 to 6.1% in 20147, although some studies showed no increase in recent years. The question arising in this context is whether the prevalence increase over the last years is true or whether it is just the result of the heightened attention from the public, media and scientific community. Using nationwide claims data containing data for approximately six million children we examined a) temporal trends of ADHD administrative prevalence estimates during 2009 to 2016; b) regional variations in ADHD prevalence, including small-area variations, and c) sociodemographic factors on the individual and district level associated with an increased chance of ADHD diagnosis.Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder primarily affecting children and adolescents (from here on referred to as children). There is probably no other mental disorder more controversially discussed both by the public and scientific community. First, prevalence varies substantially between and within countries. ADHD appears to be a public health issue in western countries with the highest prevalence estimates reported in the US and lowest in African and Asian countriesi.e. children living in districts with a lower probability of getting an ADHD diagnosis would have a 1.36-times higher chance to be diagnosed with ADHD if he/she would move to a district with a higher probability of getting an ADHD diagnosis.The dataset consisted of approximately six million children residing in 402 districts Table . This maThe administrative prevalence of ADHD did not show an increasing trend Fig. . The k-mBoys were three-times more likely to be diagnosed with ADHD than girls Table . The cha9. However, our finding is in agreement with results from other international studies. For example, in a metaanalysis of 135 cross-sectional studies conducted at different timepoints Polanczyk et al. did not observe an increase in ADHD prevalence over the last 30 years2. They concluded that variability in ADHD prevalence estimates is predominantly explained by methodological differences of the studies2. We used claims data of several years and applied standardized methodology (e.g. in terms of a study population and a case definition). Controlling for such methodological differences apparently resulted in the absence of prevalence increase.Using nationwide claims data of approximately six million children in Germany we examined regional differences in ADHD administrative prevalence, its temporal trends and factors on the individual and district level associated with a higher chance of ADHD diagnosis. In contrast to other studies we observed no increase in administrative prevalence of ADHD in Germany over the years 2011 to 2016. This trend was relatively stable across sex and administrative districts. Most of the districts displayed a similar temporal pattern. Globally, findings regarding temporal trends in ADHD prevalence are controversial. For example, two US studies reported a considerable increase of parent-reported ADHD diagnosis made by a health professional from 2003 to 20111. Second, we observed small-area differences in ADHD prevalence which decreased over the years but were still substantial in 2016. Multilevel regression analysis showed that the individual probability of being diagnosed with ADHD was also dependent on children’s residence. The corresponding MOR from the empty model was 1.36, meaning that children were 1.36-times more likely to be diagnosed with ADHD if they would move from a district with a lower ADHD prevalence to a district with a higher prevalence. We examined which factors might explain regional differences by controlling for individual- and district-level variables in a two-level regression model. The associations of ADHD diagnosis and sex and age were similar to those shown in other studies. On the district level we also found the availability of paediatric psychiatrists and paediatricians significantly associated with being diagnosed with ADHD. It can be thus concluded that the regional variation in ADHD prevalence can partly be explained by both, under- and over-diagnosing. The association of a higher risk of ADHD diagnosis and a lower proportion of migrants indicates to an underdiagnosing problem as mentioned above. On the other side, the positive association of ADHD diagnosis and the availability of psychiatrists may be a result of over-diagnosing. The latter has already been observed in several studies. For example, a US study identified that the risk of diagnosis with autism increased among children who moved into neighbourhoods with a better access to health care10. Overall, the examined variables on the district level only explained part of the regional variation. Other factors such as smoking, alcohol consumption or stress during pregnancy, or exposure to lead or polychlorinated biphenyls, which may vary geographically, may explain further regional variations in ADHD prevalence.We found substantial regional variations in ADHD prevalence. First, children living in rural areas were more likely to be diagnosed with ADHD than their counterparts from urban areas. However, after controlling the model for the proportion of foreign citizens on the district level – which was taken as proxy for individuals with migration background – this effect was strongly diminished. Apparently, children from migrant families may be underdiagnosed either due to a poor access to health care facilities and/or cultural differences in perception of ADHD-related symptoms. The latter is confirmed by systematic reviews which reported higher prevalence estimates in industrialized countries such as the US as compared to African and Asian countries11. We may thus slightly overestimate the prevalence regarding the total German population. Second, routinely collected claims data are secondary data collected for purposes other than e.g. prevalence estimation. It is well known that physicians may misdiagnose ADHD, although considerable efforts have been done in Germany to improve diagnostics and therapy of common mental disorders, including ADHD. One of them is introduction of the Psychotherapist Law in 1999 in Germany according to which psychological psychotherapists and psychotherapists specializing in children and adolescents were integrated into the ambulatory health care services. This resulted in the improvement of health care of patients with mental disorders. In addition, children are regularly examined by paediatricians from local public health services. Paediatricians work in close cooperation with nursery-school teachers and school teachers and in case of a suspicious ADHD a child is transferred to a specialist. In spite of these improvements, the risk of misdiagnosis cannot be ruled out definitively. For example, a study of Wolraich et al. showed that a substantial proportion of US paediatricians do not follow the clinical guidelines for diagnosis and treatment of children with ADHD12. In this study every fifth paediatrician does not use formal diagnostic criteria of ADHD and every third paediatrician does not use rating scales. Bruchmüller et al. examined the extent of under- and overdiagnosis of ADHD among paediatric psychotherapists in four German Federal States13. They observed that around 20% of children who fulfilled diagnostic criteria of ADHD did not receive an ADHD diagnosis, i.e. underdiagnosis. On the contrary, around 17% of children who do not fulfil the diagnostic criteria received falsely ADHD diagnosis, i.e. overdiagnosis. As a result, true prevalences may be under- or overestimated. To minimize the latter we applied a conservative definition of ADHD case. An alternative approach to estimate ADHD prevalence is a cross-sectional study design involving parents. However, relying solely on parental reports may be prone to bias . Epidemiological studies should rather use standardized instruments, including structured interviews with parents and if possible with teachers and rating scales14. Third, due to the large sample size we were able to carry out robust small-area estimations. For example, the average sample size across all districts was 15,000 children. The absolute number of ADHD cases varied between 91 and 9373 across districts with an average of 650 cases, indicating that even in a district with the lowest number of ADHD cases (n = 91) we were able to provide robust estimates of ADHD prevalence.First, we used claims data containing information on approximately 87% of all individuals in Germany. When comparing our study population with the general German population we found minor differences in terms of sex, age and federal state distribution. Our dataset contains no information about children insured privately . Privately insured individuals tend to have a higher socioeconomic status than statutory insured individuals and may be less affected by ADHDOne of the potential limitations of this study is the lack of individual-level data such as socioeconomic status or migration background. On the individual level the dataset contained only information on ADHD diagnosis, sex, age and place of residence. This was compensated by the application of multilevel modelling where we used aggregated data on the district level obtained from the literature. However, multilevel models can be prone to aggregation bias and thus need to be considered with caution.The administrative prevalence of ADHD among children in Germany did not show an increasing trend in recent years. However, there were considerable regional differences which remained significant after adjusting for demographic factors on the individual and socioeconomic factors on the district level. There is indication that migrant children may be underdiagnosed or less affected by this disorder. Further research is needed to investigate factors explaining remaining regional variations in ADHD prevalence in Germany.e.g. sociodemographic status or migration background), we used publicly available data on the district level, including (a) socioeconomic deprivation index15, (b) density of paediatric psychiatrists, (c) density of paediatricians, i.e. number of physicians per 100,000 citizens16, and (d) proportion of individuals with a foreign citizenship17.We used ambulatory claims data of all statutory health insured children between 5 and 14 years of age in Germany in the years 2009 to 2016 . It is estimated that around 87% of the total German population is insured statutory; the remaining 13% of the population is insured privately. Claims data contain outpatient diagnoses of individuals who contacted physicians at least once per year. Diagnoses are coded according to the German modification of the International Classification of Diseases (ICD-10-GM). In addition, claims data contain information on individual’s sex and age and place of residence . Because no other information on the individual level is available in claims data . We considered a child having an ADHD if he/she had been diagnosed in at least two quarters of the corresponding year. This was done to reduce the proportion of false positive diagnoses as it is known that using coding the diagnosis only in one quarter of the year may overestimate the true prevalence.We used the code ‘F90 – hyperkinetic disorder’ with all subcodes  residing in 402 districts (level 2) to examine individual- and district-related factors associated with ADHD diagnosis. We controlled the model for sex and age on the individual level and for: (a) socioeconomic deprivation index15, density of (b) paediatric psychiatrists and (c) paediatricians, i.e. number of physicians per 100,000 citizens16, (d) proportion of individuals with a foreign citizenship17, and (e) children’s place of residence with four categories  on the district level. Initially, we examined whether there was variation in ADHD diagnosis across districts; this was done in a model without predictors (i.e. null model). We calculated median odds ratio (MOR) as an indicator of unexplained community heterogeneity18. Then, we included all above mentioned variables and calculated the MOR again to examine whether the variables explained part of the variance in ADHD prevalence across the districts. Analyses were performed with STATA, version 15  and the R Foundation for Statistical Computing, version 3.3.3. The R packages “spdep” and “KmL” were used to examine spatial autocorrelation and prevalence trajectories, accordingly.Initially, we calculated crude- and sex-specific prevalences of ADHD. Furthermore, we used the Global and Local Moran’s I test to examine spatial autocorrelationThe use of claims data for scientific research is regulated by the Code of Social Law (SGB X) in Germany. According to this law, an ethical approval and informed consent are not required as these are routinely collected pseudonymized data.


ADHD) symptoms in a cohort of patients with schizophrenia (SCZ).To investigate the frequency of childhood and adult attention deficit hyperactivity disorder (ADHD and childhood ADHD symptoms in 126 patients with ICD‐10 diagnoses of SCZ.A systematic review was conducted to evaluate existing evidence. Two self‐report questionnaires were used to investigate adult ADHD in SCZ subjects ranging between 17–57% and 10–47% respectively. Within our cohort, 47% of patients reported positive screening for ADHD symptoms either in childhood or adulthood. 23% reported symptomatology consistent with both childhood and adult ADHD.Five studies were included in the systematic review, with the prevalence of childhood and adult ADHD symptomatology in SCZ compared to that reported for ADHD in the general population. Our findings highlight the importance of improved clinical assessment and treatment considerations in a subgroup of patients with SCZ.We demonstrate a greater presence of  SCZ is defined by the presence of psychotic symptoms, disorganised speech/behaviour and negative symptoms, such as avolition and alogia P = 0.0007) The presentation of SCZ can include varying degrees of attentional dysfunction Systematically review studies that have estimated the prevalence of childhood and adult ADHD in patients with schizophreniaEstimate the prevalence of childhood and adult attention deficit hyperactivity disorder symptoms in a cohort of patients diagnosed with schizophrenia (UCL genetics of schizophrenia cohort).We aimed to:th revision of the International Statistical Classification of Disease and Related Health Problems) We systematically reviewed the literature relating to the prevalence of childhood ADHD (cADHD) and the persistence in adulthood of the condition (c+aADHD) in patients with SCZ using the PRISMA criteria MEDLINE and PsycINFO were searched via OvidSP using the terms:  on, 29 May 2018. A manual search of the literature was also conducted. Only studies reported in English were considered for the review. Study selection was performed by two reviewers (IA and GG).The outcome measures were the percentage of patients with SCZ that had a clinical diagnosis of ADHD or ADHD symptoms, as determined by interviews and self‐report. A data extraction table capturing the relevant information was developed. Data items extracted included: the number of trial participants, the age range of participants, method of diagnosis of trial participants, methods for assessing the occurrence of ADHD symptoms in trial participants and the outcome measure of prevalence.The SCZ cohort of the UCL DNA Polymorphisms in Mental Illness (DPIM) has been described previously Validated tools were used for the assessment of cADHD symptoms and adult ADHD symptoms (aADHD). The 25‐item version of the Wender Utah Rating Scale (WURS) provided information about symptomatology consistent with cADHD based on DSM criteria OPCRIT and/or SADS‐L data were available for 106 of 126 of the participants with SCZ. The earliest age when medical advice was sought or the age of onset of first psychiatric condition (AOO), the age at study entry (ASE), the presence of cannabis abuse/dependence, the presence of alcohol abuse/dependence, the presence of any abuse/dependence , a family history of SCZ, a family history of other psychiatric condition and the length of schooling were extracted from the phenotypic data and used as covariates.Stata (version 14) was used for all statistical analyses The total scores for the WURS and ASRS were calculated for each participant. Data imputation was performed using the subject's average score for the questionnaire affected. A suitable cut‐off for each scale was applied to dichotomise the data for analysis. As there was no evidence for the best WURS cut‐off score in patients with SCZ, we used a cut‐off at 46 of 100 due to its greater discriminatory power in patients with unipolar depression The ASRS has a maximum score of 30 (six questions with maximum score of 5). Each question has a different ‘cut‐off’ for what is classified as a significant symptom, so for one question it might be 3/5 and for the other 4/5. If a person achieves the cut‐off in four of the six questions, they are considered to have symptoms that are highly consistent with ADHD in adults, warranting further clinical investigation U‐test following assessment for normality. A one‐way analysis of variance was used to compare groups of participants with different lifetime prevalences of ADHD symptomatology for AOO and ASE. Linear regression of these covariates with WURS and ASRS scores was also carried out to confirm the association.To compare the means of continuous variables, we utilised either the t‐test or the nonparametric Mann–Whitney U‐test was utilised to compare whether scoring of each questionnaire was affected by different covariates. To confirm these findings, linear regression was carried out on those covariates that produced indicative significance at the 5% level.The Mann–Whitney The systematic search identified 299 studies. After removal of duplicates, and filtering to English‐only studies, 226 studies remained. Title and abstract screening identified 10 studies for detailed review. Five articles fulfilled our inclusion criteria, three following the above literature search and 2 from a manual search of databases and reference lists of articles.Prevalence estimates for cADHD in patients affected by SCZ ranged from 17 to 57%. Only two studies measured the prevalence of ADHD comorbidity in adulthood, reporting 10% and 47%, respectively, see Table Consent‐to‐participate forms were received from 194 of the 1000 participants invited to take part. Questionnaires were received from 131 subjects; 5 (3.8%) had to be excluded due to the level of missing data leaving a final sample size of 126 (83 (65.9%) men and 43 (34.1%) women). Of these participants, 10 (7.9%) required imputation for one value, 9 (7.1%) for two values and 3 (2.4%) for three missing values. Participants included in the study were aged 21–85.Twenty‐three per cent of participants with SCZ reported symptoms of ADHD in childhood persisting through to adulthood. Symptoms of cADHD only were reported by 11.1%, and aADHD only by 12.7%. The remaining 53.2% of participants reported no ADHD symptoms. In total, 34.1% of 126 subjects with SCZ reported symptomatology consistent with childhood ADHD. Table P = 0.60) or ASE (P = 0.40) in any of the four ADHD symptom groups . A linear regression of AOO with ASRS or WURS scores also showed no significance (P < 0.05).As part of the phenotypic data set collected for the DPIM study, information on the AOO was available for 106 participants and ASE for 99. A one‐way analysis of variance revealed no significant difference in the AOO  and ASRS (P = 0.0015) was significant, and a linear regression of ASRS scores on a history of alcohol abuse showed a significant association, F  = 8.99, P = 0.0034.Univariate linear regression analyses were carried out for variables with significant associations at the 5% level in Table A systematic review of the published literature of ADHD symptomatology in schizophrenia patients identified only five previous studies, with small sample sizes and heterogeneous study methodologies. For example, Hallerbäck et al. and Donev et al. had a sample size of 41 and 27 patients respectively In our cohort, we found 23% of participants with SCZ to have symptomatology consistent with c+aADHD, increasing to 34.1% when including cADHD only. Despite the heterogeneity in the studies of ADHD in SCZ, all estimates of ADHD prevalence and our estimate of symptomatology indicate that ADHD is more common in SCZ than in the general population. The general population prevalence of ADHD diagnosis has been estimated to be 5.3% in childhood and 2.5% in adults Current diagnostic criteria for ADHD require the onset of symptoms in childhood, that is, before the age of 12 in DSM‐5 and before the age of 7 according to the ICD‐10. Interestingly, although 35.7% of participants with SCZ reported aADHD symptoms, 12.7% did not report symptomatology suggestive of cADHD. Longitudinal studies of epidemiological cohorts in Brazil Despite AOO being conceptualised as a surrogate measure of severity There is currently a lack of recommended pharmacological treatments for people experiencing comorbid SCZ and ADHD This study has multiple limitations which must be acknowledged. First, the sample size was modest, but is similar to comparable studies in the literature. More precise estimates of the prevalence of cADHD and/or aADHD in SCZ will require much larger sample sizes. Second, the sample comprised of participants who volunteered to take part in the DPIM study and responded to the invitation to take part in the study extension exploring the prevalence of inattentiveness, hyperactivity or impulsiveness in people living with schizophrenia. The response rate was below 20%. Moreover, the participants had to complete and return two letters. These factors likely biased the cohort towards people with higher levels of functioning and may impact the applicability of the study data to other settings.Third, the gold standard assessment for ADHD in adults is the Diagnostic Interview for ADHD in Adults (DIVA) We report a higher prevalence of ADHD symptoms in patients with SCZ, as compared to the prevalence of ADHD symptoms within the general population. These findings likely reflect a degree of overlapping symptomatology for the two disorders and also some of the shared genetic aetiology that has been identified in recent genomewide association studies Dr Giovanni Giaroli has received honoraria for acting as a consultant and speaker and for travelling by Shire, Eli Lilly, Flynn Pharma and Janssen.


Bartonella species in Egyptian fruit bats (Rousettus aegyptiacus) and bat flies (Eucampsipoda africana) from these caves and assessed whether Bartonella infections had occurred in persons from the surrounding communities. Our results indicate that these bats and flies harbor Bartonella strains, which multilocus sequence typing indicated probably represent a novel Bartonella species, proposed as Bartonella rousetti. In serum from 8 of 204 persons, we detected antibodies to B. rousetti without cross-reactivity to other Bartonella species. This work suggests that bat-associated Bartonella strains might be capable of infecting humans.Twice a year in southwestern Nigeria, during a traditional bat festival, community participants enter designated caves to capture bats, which are then consumed for food or traded. We investigated the presence of  Pteropodidae) are used as food, for either cultural reasons or subsistence ; colony sizes can reach >1,000  to understand risk factors and the occurrence of pathogen spillover from bats to humans. We examined whether bats and ectoparasites of these bats within the caves used in the Idanre bat festival are infected with Bartonella, characterized any Bartonella species identified in bats or bat flies, and screened human serum samples for evidence of Bartonella infection.During 2010 and 2013, we researched the health risk to humans participating in the Idanre bat festival. We sampled bats and their ectoparasites from the caves and used them to identify a variety of zoonotic pathogens, including Human subjects work was approved by the Centers for Disease Control and Prevention (CDC) Institutional Review Board, the Ahmadu Bello University Human Ethics Board, and the National Health Research Ethics Committee of Nigeria. All animal procedures were conducted in compliance with a field protocol approved by the CDC Animal Institutional Care and Use Committee.R. aegyptiacus). Captured bats were anesthetized by intramuscular injection of ketamine hydrochloride (0.05–0.1 mg/g bat weight) and exsanguinated via cardiac puncture after surface sterilization with 75% alcohol. Serum and blood clots were separated by centrifugation. Clots were stored at −80°C except while still in the field or being shipped, during which time they were stored on dry ice. We captured bats by nets in 2 caves in Idanre Hills, Ondo State, southwestern Nigeria, in September 2010 (n = 106) and February 2013 (n = 71). We identified all bats by morphologic characteristics as Egyptian fruit bats  (B. doshiae) and negative (deionized water) controls were included to ensure that the PCR worked properly.We prepared crude genomic DNA by heating a heavy suspension of pure culture for 10 minutes at 95°C, followed by centrifugation of the lysed cells for 1 minute at 3,000 rpm. The supernatant was then transferred to a clean centrifuge tube to be used as the template DNA. We first verified all isolates obtained from the blood clots as gltA in both directions by using an ABI 3130 Genetic Analyzer . We used the Lasergene software package  to compare the generated gltA sequences with all available Bartonella species/genotypes. Once the sequences were identified, we selected 1 representative strain (R-191) for further characterization with multilocus sequence typing on the basis of sequence analysis of 8 molecular markers  , we homogenized whole ectoparasites in Navy Eppendorf bead tubes (Next Advance) containing 400 μL brain–heart infusion broth . We extracted DNA from the homogenates by using the KingFisher Flex Purification System and the associated MagMAX Pathogen RNA/DNA Kit  according to the manufacturer’s protocols. Detection of 6 agar-grown organisms) of the Bartonella strain (R-191) obtained from Egyptian fruit bats. Both were put into T-150 flasks that contained minimum essential medium supplemented with 10% fetal calf serum, 10 mmol HEPES buffer solution, 10 mmol nonessential amino acids, and 2 mmol L-glutamine. The flasks were incubated at 35°C and harvested on postinoculation day 4. At harvest, all but 2 mL of the medium was removed from the flask, sterile glass beads were added, and the flask was gently rocked to remove the Vero E6 cell monolayer. Drops (≈15 μL) of the cell suspension were mounted on each well of 12-well glass slides, which were then air dried, fixed in acetone for 15 minutes, and stored at −70°C until use.We produced a whole-cell antigen by co-cultivating Vero E6 cells with the pure culture ; not all of these persons had participated in all bat festival activities. Participants were asked about their contact with bats and their role in the festival, and some provided a blood sample (considered an acute-phase specimen). About 69–78 days later, a follow-up survey was conducted and a second blood sample  was collected . Serum and blood clots were separated by centrifugation; serum was stored at −80°C except while in the field or being shipped, during which time it was stored on dry ice.Bartonella antigen from the bat-associated isolate. Antigen-covered wells of the slide were overlaid with dilutions of human serum. Separate slides were included with positive and negative controls. The positive control against the Egyptian fruit bat–associated Bartonella species was produced in laboratory mice via mouse immunization with heat-inactivated bacterium . All slides were incubated at 35°C for 30 minutes and then washed in phosphate-buffered saline for 15 minutes. We used anti-human and anti-mouse conjugates  for human and control serum samples, respectively. Each human serum sample reactive at the initial dilution was further titrated in 2-fold dilutions to endpoint; to check for cross-reactivity, we tested the final positive samples (defined as a titer >1:64) for 3 other Bartonella antigens  previously reported in Africa  to each other and represented 4 unique variants . A variant is defined when it differs by >1 nt from others. Together with Bartonella strains obtained from Egyptian fruit bats in Kenya  with 7 additional genetic loci  further confirmed the uniqueness of this strain. Sequencing information for each genetic marker demonstrated that the Bartonella strain from the Egyptian fruit bats was distant from all other known Bartonella species and genotypes, including those reported from other bats from Africa. Sequences of all genetic loci obtained during the analyses were deposited in GenBank . We compared the fragment sequences of each target with those from other Bartonella species/genotypes. The Egyptian fruit bat–associated Bartonella formed a separate genetic group that was distant from all other Bartonella species with >20% genetic distance and probably represents a novel Bartonella species, according to the definition of La Scola et al.  as the natural host. A phylogenetic tree based on the ITS locus illustrates the relationship of this proposed novel species to other Bartonella species (Multilocus sequence typing of the type strain ( species .Eucampsipoda africana Theodor (Diptera: Nycteribiidae). The morphologic identification of every bat fly was confirmed by 1 or both mitochondrial markers (16S rRNA or COI). Representative 16S rRNA (accession nos. MH138030–MH138037) and COI (accession nos. MH151059–MH151066) sequences have been deposited in GenBank.In 2013, we collected 51 ectoparasites from Egyptian fruit bats. With the exception of 1 unidentified mite, all arthropods were identified as the bat fly >1 ITS or gltA sequence that was confirmed via BLAST (https://blast.ncbi.nlm.nih.gov/Blast.cgi) as Bartonella. Positive samples yielded 19 ITS sequences and 18 gltA sequences; 16 samples yielded sequences for both loci and 5 samples yielded only 1 sequence. All but 1 of the 19 ITS sequences matched closely to the proposed B. rousetti (>95% sequence identity) (B. tamiae (DQ395180). Of the 18 (66.7%) gltA sequences, 12 were close matches for B. rousetti (>98.3% sequence identity); all 12 of these samples also produced ITS sequences matching this strain.Of the 50 DNA extracts from bat flies, 21 (42%) produced gltA sequences were identical to Bartonella sequences detected in a louse (Neohaematopinus sciuri) collected from a dead Eastern gray squirrel (Sciurus carolinensis) at a zoo in Greenville, SC, USA (GenBank accession no. EU368000) and an unidentified tick collected from a sheep in Peru (GenBank accession no. AF415209). These sequences were also closely (>99% sequence identity) related to other sequences from fleas  collected from dogs in Tunisia (GenBank accession nos. KP126468–74), a louse pool (Polyplax spp. and Hoplopleura spp.) collected from rodents in Thailand (GenBank accession no. KT324560), and an unidentified flea collected from a dog in Peru (GenBank accession no. GU583843). Of the specimens with this particular gltA sequence, 2 yielded no ITS sequence, 3 yielded ITS sequences matching B. rousetti, and 1 yielded the single B. tamiae sequence. Representative ITS (GenBank accession nos. MH14262–MH142639) and gltA (GenBank accession nos. MH151067–79) sequences for each novel sequence variant were submitted to GenBank.The remaining 6 B. rousetti; 12 samples from different persons showed reactivity at an initial dilution of 1:32. Further 2-fold titration confirmed that 8 were positive, with titers >1:64  in Africa  exhibit a high level of serologic cross-reactivity  that circulate in Africa, and we did not detect any positive results. Given that immunofluorescence assays have good discriminatory ability for a wide range of antigens . Instead, human exposure may potentially occur via other routes, such as 1) directly by bat bites or scratches, which is similar to how humans acquire infections with B. henselae through cat scratches (Bartonella DNA in bat feces (Bartonella DNA in bat saliva and urine, providing support for routes 1 and 2 above, although no attempts have been made to culture viable bacteria from these fluids. However, viable Bartonella bacteria have been cultured from experimentally infected ectoparasites, including fleas and bedbugs (Bartonella could spread from infected mammalian hosts through multiple routes. Therefore, it may not be necessary for humans to interact directly with live bats to be exposed to bat-associated Bartonella. Persons might be at risk when interacting with bat carcasses, guano, or other contaminated products. Of note, we do not provide definitive evidence of the route of exposure for any of the 8 seropositive participants. Indeed, 3 of these participants reported no interactions at all with bats.All known species of B. rousetti in humans, and vector competency of bat flies for transmitting Bartonella. Results should provide guidance to communities for mitigating the risks to humans interacting with animals and their arthropod vectors.Future studies should continue to evaluate the relative correlations of exposure routes, the pathobiology of batborne


Attention deficit hyperactivity disorder (ADHD) is defined as childhood neurobehavioural disorder. Due to short attention span, oral hygiene and dental treatment of such individuals can be challenging. Aim of this study was to evaluate the oral health of children and adolescents with and without ADHD living in residential care in rural Rhineland-Palatinate, Germany.Included in the study were 79 participants  living in residential care: 34 participants with ADHD and 45 participants without ADHD (control). Oral examination included the following parameters decayed, missing, filled teeth in the primary dentition (dmft), decayed, missing, filled surfaces/teeth in the secondary dentition (DMFS/DMFT), approximal plaque index (API), bruxism and orthodontic treatment. Additionally, oral hygiene, last dental visit and treatment performed, and dietary habits were assessed by questionnaire.There were no significant differences in dmft, API, bruxism and oral hygiene habits between groups. However, participants with ADHD tended to have higher DMFS/DMFT values than the control group. Ongoing orthodontic treatment was found more often in the control group. The ADHD group tended to consume acidic/sugary beverages and sweet snacks more often than the controls. Different treatments  were performed at the last dental visit in the two groups., oral health was similar in children and adolescents with or without ADHD from the same residential care setting. Parents/guardians need instructions for better supervision of oral hygiene and dietary habits to improve the poor oral health of children with or without ADHD.Within the limitations of this study Attention deficit hyperactivity disorder (ADHD) is one of the most common neurobehavioural disorders of childhood, which can persist into adolescence and adulthood. The prevalence of ADHD ranges from 2 to 18%  in distuIt has been shown that children with ADHD have overall a poorer oral health status , 6 and oXerostomia is mentioned as one of the adverse orofacial side effects of most drugs, which are commonly used for pharmacological treatment of ADHD . Lower uConcerning dietary habits, it was shown that there was a trend for more children with ADHD to eat sweet snacks , 13 or dRegarding dental caries, Kohlboeck et al.  reportedDue to the characteristic features of ADHD, oral hygiene and dental treatment of children and adolescents with ADHD can be a challenge. The aim of the study was to assess oral health parameters of children and adolescents with or without ADHD living in residential care under supervision of specially trained caregivers. The null hypothesis was that oral health parameters of children and adolescents with or without ADHD, living in the same residential care setting under similar conditions, will not be different.This study was conducted among children and adolescents, living in residential care in a rural area in Rhineland-Palatinate, Germany, due to familial problems, including loss of a parent or domestic violence. The children only spend a limited time in the residential care setting, where they live in small groups together with guardians. They ate two of their meals  in this setting, while the main meal at lunch time was either consumed in the school cafeteria or in the residential care setting. Oral hygiene measures twice daily after breakfast and before bedtime were supervised by the guardians. The children went for dental consultation visits to various dentists, none of whom was specially trained for treating children with special needs. Some of the children and adolescents were permitted to spend the weekend one to three times per month in their family home. All participants were examined to assess oral health conditions as well as oral hygiene and dietary habits. This study was part of a group prophylaxis program for children and adolescents in Rhineland-Palatinate, Germany, where yearly dental examinations are conducted. Prior written consent was obtained from all parents or guardians of participating children and adolescents; participation in the study was voluntary. This study comprised two groups of children and adolescents: one group with children and adolescents with ADHD, and as control group children and adolescents without ADHD. The examiner was informed about which participants belonged to the ADHD group only after the study was completed. However, in most cases, due to the erratic behaviour of the ADHD participants, the diagnosis could be suspected.< 50, eating disorders and missing written consent for participation.The age of the children and adolescents with ADHD living in this residential care setting ranged from 9 to 15 years, with one child aged 6 years. The age of the children and adolescents without ADHD ranged from 8 to 18 years. To match the two groups for age and sex, only participants aged 9–15 years and both sexes were included in this study. The ADHD group included children and adolescents with diagnosed ADHD by their paediatricians according to the classification ICD-10  F90.0 (dAll participants of the study were examined by the same investigator (SW), who was previously trained by a paediatric dentist (BA). Dental examinations included decayed, missing, filled surfaces/teeth in the secondary dentition (DMFS/ DMFT), decayed, missing, filled teeth in the primary dentition (dmft), and API  according to Lange et al. . Only caA comprehensive questionnaire was developed and used in this study to assess oral hygiene and dietary habits . For categorical variables  only absolute and relative frequencies are given as descriptive information. For numerical continuous and discrete variables  mean, standard deviation (SD), median, minimum (min), maximum (max), and frequencies were calculated. Comparisons between ADHD group and control group for categorical variables were performed using the Chi-square test; for comparisons of numerical variables the non-parametric Mann-Whitney In this study, a total of 79 children and adolescents was examined, 34 of them with ADHD and 45 without ADHD, which served as control group. Table p = 0.39).In the ADHD group 12 of 34 participants had primary teeth with a mean dmft of 0.33 ± 0.89  and in the control group 15 of 45 participants had primary teeth with a mean dmft of 0.47 ± 0.83 . There was no statistically significant difference between the two groups (p = 0.722) and DMFT (p = 0.983).The permanent teeth were assessed for DMFS and DMFT Table . The meaHowever, differences for DMFS and DMFT values were found when the two groups were analysed separately for the various age groups 9 to 15 years). The scatterplot presented in Fig. 5 years. p = 0.980), the percentages are high in both groups and reflect an oral hygiene which is at best fair and needs to be improved.The assessment of oral hygiene showed that the ADHD group had a mean API of 51.9 ± 16.4% and the control group had a mean API of 52.1 ± 16.7% (Table p = 0.502).Gingivitis was diagnosed only in a small number of participants, in three (8.8%) with ADHD and in seven (15.6%) in the control group Table , whereasp = 1.000); in the ADHD group, 19 participants (55.9%) had bruxism, and in the control group were 25 participants (55.6%) with bruxism (Table p = 0.182). Only two participants in the ADHD group (5.9%) had ongoing orthodontic treatment and four of them (11.8%) needed orthodontic treatment. In contrast, eight participants (17.8%) in the control group received ongoing orthodontic treatment and only two of them (4.4%) needed orthodontic treatment. Both in the ADHD group and in the control group the majority did not need any orthodontic treatment: 28 participants (82.3%) in the ADHD group, and 35 participants (77.8%) in the control group.The presence of bruxism was similar in both groups (p = 0.399). Tooth brushing only in the morning reported one individual from the ADHD group (2.9%) and three from the control group (6.7%); and tooth brushing only in the evening was practiced by three participants in the ADHD group (8.8%) and one from the control group (2.2%). No tooth brushing was only reported by one person from the control group (2.2%).The results concerning oral hygiene habits are shown in Table p = 0.971). In both groups, only one participant used fluoride-containing toothpaste with 500 ppm (2.9% of the ADHD group and 2.2% of the control group). One participant of the ADHD group (2.9%) and two of the control group (4.4%) gave no answer which toothpaste they used. Fluoride gel was known to 52.9% of the ADHD group and to 55.6% of the control group (p = 0.824). However, most of the participants did not use fluoride gel .Fluoride-containing toothpastes with 1000–1490 ppm fluoride were used by almost all of the participants . Frequent intake of acidic/sugary beverages (at least more than 3 times per week to twice or three times daily) was reported more often (41.4%) in the ADHD group versus 33.3% in the control group (p = 0.348).Dietary habits in the ADHD group and the control group are summarized in Table p = 0.378). The preferred sweets eaten between meals and frequency of intake are listed in Table Similar numbers of participants from the two groups reported that they consumed sweet snacks: 28 (82.4%) from the ADHD group and 39 (86.7%) from the control group (p = 0.291). In particular, daily consumption of sweet snacks was reported more often by participants of the ADHD group (40.7%) and by only 25.6% of the control group. In the ADHD group, 22.2% consumed sweet snacks two or three times weekly, and in the control group 38.5%. Intake of sweet snacks once a week was reported by 37.0% of the ADHD group and by 35.9% of the control group.The frequency of intake of preferred sweets differed between the two groups  had their last visit in this time span . In the ADHD group, the majority of the participants (59%) reported that it was only a control visit or that they received prophylactic measures, whereas dental therapy, which consisted of fillings, extractions and endodontic treatments, was performed on only 9% of the participants. In contrast, only 42% of the control participants had solely gone for a control visit or received prophylactic measures, whereas dental therapy was performed in 22% of the control participants, which was more than twice as many as in the ADHD participants. Orthodontic treatment was only performed on control participants (7%).The number/percentage of participants who reported that a treatment was performed during their last dental visit was similar . However, differences were seen between the two groups concerning the type of treatment  living in residential care. The null hypothesis that oral health parameters of children and adolescents with or without ADHD, living in the same residential care setting under similar conditions, would not be different, was accepted. No statistically significant difference in oral health of children and adolescents with or without ADHD living in residential care was found regarding dmft, DMFT, DMFS, API, bruxism and oral hygiene habits. In spite of these findings, participants with ADHD tended to have higher DMFS/DMFT values than the control group, the ADHD group tended to consume cariogenic drinks and food more often than the controls, and dental and orthodontic treatment was performed less often than in the control group.More boys than girls seemed to be affected with ADHD with a ratio of 4:1 , which was close to Grooms et al.  with 31 There was no statistically significant difference in the dmft/DMFT between the ADHD and non-ADHD groups, which is in agreement with the study by Hidas et al.  and ChauThe percentages of API were high in both groups, although there was no statistically significant difference between the two groups. This is similar to the findings of Chau et al. . In contThe percentage of participants consuming acidic/sugary beverages and sweet snacks was similar in the two groups. But regarding frequency of intake of acidic/sugary beverages and sweet snacks, a higher percentage of children from the ADHD group tended to consume these drinks and foods more often than those from the control group. Blomqvist et al.  reportedThe presence of bruxism was similar in both groups, which is in agreement with Hidas et al. , whereasA higher percentage of children with ADHD reported only for a dental check-up or received prophylactic measures, whereas actual dental therapy was performed more often in the control participants. Aminabadi et al.  observedDue to an unequal sample size the participants with ADHD in the present study were not divided into medicated and non-medicated patients, because the majority 76.5%) was under pharmacotherapy and only eight out of 34 ADHD children received no medication. However, this non-discrimination into medicated and non-medicated participants may have affected the results of the present study. Studies .5% was u, 23 haveOne of the limitations of the present study is the relatively small sample size of 79 participants, but which is similar to the study of Chau et al. , 6, 13 hThe findings of the present study show the need for considerable improvement of oral hygiene and dietary habits in children and adolescents, who live in residential care. In children with ADHD, the most effective method of reducing dental caries seems to be more frequent dental visits with a) instructions for better oral hygiene at home and b) dietary counselling to reduce the consumption of sweet snacks and drinks, including parents as well as guardians . In partThe findings of the present study show that there was no statistically significant difference in oral health of children and adolescents with or without ADHD living in residential care. However, ADHD participants had higher DMFT/DMFS values and consumed more cariogenic drinks and food. In addition, ongoing orthodontic treatment was performed less often in these participants. Parents and guardians need better instructions for a more sufficient supervision of oral hygiene and dietary habits in children and adolescents with or without ADHD.Additional file 1. Questions concerning oral hygiene and dietary habits.


Bartonella species that are distributed worldwide with animal and public health impact varying according to Bartonella species, infection phase, immunological characteristics, and geographical region. Bartonella is widely present in various mammals including cats, rodents, ruminants, and humans. At least 13 Bartonella species or subspecies are zoonotic. Each species has few reservoir animals in which it is often asymptomatic. Bartonella infection may lead to various clinical symptoms in humans. As described in the B.tribocorum-rat model, when Bartonella was seeded into the blood stream, they could escape immunity, adhered to and invaded host erythrocytes. They then replicated and persisted in the infected erythrocytes for several weeks. This review summarizes the current knowledge of how Bartonella prevent phagocytosis and complement activation, what pathogenesis factors are involved in erythrocyte adhesion and invasion, and how Bartonella could replicate and persist in mammalian erythrocytes. Current advances in research will help us to decipher molecular mechanisms of interactions between Bartonella and mammalian erythrocytes and may help in the development of biological strategies for the prevention and control of bartonellosis.Bartonellosis is an infectious disease caused by  Bartonella species are fastidious, Gram-negative hemotropic organisms. Bartonella have been isolated from a range of species; from diverse animals, such as canids, rodents, ruminants, and felids. They are mainly transmitted via direct contact  or by numerous arthropods such as sand flies, fleas, lice, biting flies, and ticks  is an outer membrane protein which is homologous to Yersinia adhesin A (YadA), Haemophilus surface fibrils (Hsf), Moraxella surface protein A (UspA), and Haemophilus adhesin (Hia)  and delay lysosomal targeting and destruction  mutants, while not the wild type B. birtlesii. Moreover, anti-BadA antibodies could neutralized this killing activity and ΔbadA was resistant to heat-inactivated serum  formation or via phagocyte opsonization. It was considered that the absence of O-side chain of Bartonella LPS, flagellin, and BadA could inhibit the function of the immune system, such as the complement and phagocytic cells, the inflammatory response decreased resulting in reduced phagocytes migration, antigen presenting, and B cells activation.Since Brucella suis BmaC, BtaE, and BatF adhesins  found in certain s Figure .Bartonella could then adhere to and invade erythrocytes quickly  mutant, a leucine-isoleucine-valine (livG) mutant, and seven mutants for genes encoding Trw components. When we horizontally transferred the trw locus of rat-specific B. tribocorum into human-specific B. quintana and cat-specific B. henselae, they were able to interact with rat erythrocytes, suggesting that the Trw sytstem is a key factor of erythrocyte infection and host specificity.Recently, the function of Trw in erythrocyte infection was identified by an trw genes of Bartonella species are collinear with their homologous genes of plasmid R388, except for the gene duplications of trwJ-I-H  and trwL (the virB2 homolog)  Figure . For exas Figure . The dupy Dehio, .B. birtlesii surface and could bind to band 3 of mouse erythrocytes. It was considered that TrwL might also bind to the surface of erythrocytes, and the outer membrane parts of TrwL proteins might be responsible for this ability. Further studies are required to identify the erythrocytic receptors of TrwL. Bacteria usually use some virulence factors to bind to host cells more intimately after initial adherence. We considered that the specific and stable interactions between Bartonella and host erythrocytes were mediated by both TrwJ and TrwL. Moreover, TrwJ might have the capability to interact with TrwL, which represents the major and minor pilus  and the heme utilization locus (Hut) to sequester heme nucleoside polyphosphate hydrolase of the MutT motif family  and transmitted from cats to humans by cat scratches or bites (Chomel et al., Bartonella infection.Bartonella infects host erythrocytes, many uncertain aspects need further studies. The functions of the above-mentioned strategies and virulence determinants are still not fully elucidated and many other virulence factors have yet to be found. Moreover, the gene expression, regulation, and signal transduction pathways of those factors are still elusive. We also know little about the physiological changes and recognition receptors of erythrocytes during their infection.Despite significant amounts of effort and advances to understand the molecular mechanisms of how In summary, with so many exciting and important questions yet to be answered, future studies would not only better clarify the functions of the factors, but also increase our understanding of the network between the factors and erythrocytes at a molecular level.HD, QP, and BZ wrote the initial draft of the paper. HD and MV-T organized and proofread the paper. BZ helped to draft the figure. HD approved the version to be published. All authors read and approved the final manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Five hundred years have passed since the death of Leonardo da Vinci, and much has been written about him. Leonardo the artist, the scientist, the architect, the inventor, whose genius has been perceived as the allure of an unfathomable riddle. But some of the words written about Leonardo after he died at Clos-Lucé in France on 2 May 1519, hint at a very different man to the one many of us presume to know. According to his first biographer Giorgio Vasari, Leonardo died lamenting ‘that he had offended God and mankind in not having worked at his art as he should have done’ .The story of Da Vinci is one of a paradox—a great mind that has compassed the wonders of anatomy, natural philosophy and art, but also failed to complete so many projects . The exc‘in learning and in the rudiments of letters he would have made great proficiency, if he had not been so variable and unstable, for he set himself to learn many things, and then, after having begun them, abandoned them.’ .His difficulties with focusing became even more evident later in adolescence, when he moved from the small village of Vinci to Florence in the workshop of Andrea Verrocchio. Verrocchio, a true Renaissance man, shared Leonardo’s wide breadth of interests and eclectic talent. But Leonardo lacked his master’s rapid power of execution and organizational skills. Leonardo’s first important commissioned works, some obtained through his father’s connections, were prepared at length but quickly abandoned. Other programmed works were never started. Leonardo's struggle to work independently as an artist might also explain his unduly prolonged stay in the Verrocchio workshop lasting until the age of 26 when he probably managed to set up his own independent studio in Florence. On 10 January 1478 he received his first recorded commission as an independent painter, a large altarpiece to hang in the Chapel of San Bernardo. For this prestigious commission he obtained a cash advance of 25 florins, but he never delivered the work . ProbablAt the court of Ludovico il Moro, the future Duke of Milan, he astounded his patrons with the most ambitious ideas and projects, but failed to gain their trust in his ability to deliver on time. Even when Leonardo was finally commissioned with the important project of building a bronze statue of Ludovico’s father, the future Duke asked his allied Lorenzo il Magnifico if he could indicate a more apt Florentine artist for the project because he ‘doubted Leonardo’s capabilities to bring it to completion’ .Last Supper ? ADHD is a highly heritable childhood behavioural disorder characterized by continuous procrastination, the inability to complete tasks, mind wandering and a restlessness of the body and mind . ArguablWe suggest that historical documentation supports Leonardo’s difficulties with procrastination and time management as characteristic of ADHD, a condition that might explain aspects of his temperament and the strange form of his dissipative genius. Leonardo’s difficulties were pervasive since childhood, which is a fundamental characteristic of the condition. There is also unquestionable evidence that Leonardo was constantly on the go, keeping himself occupied with doing something but often jumping from task to task. Like many of those suffering with ADHD, he slept very little and worked continuously night and day by alternating rapid cycles of short naps and waking.In modern neuroscience, problems with executive functions are thought to underlie procrastination and impaired concentration. Neuroimaging studies of children and adolescents with ADHD indicate differences in regions of the frontal lobe and basal ganglia responsible for executive functions and impulse control. About two-thirds of children with ADHD continue to have behavioural difficulties in adulthood, which can be ameliorated with therapy . There iAnd what is the possible link between left-handedness, dyslexia, ADHD and artistic abilities? Some epidemiological studies indicate that left-handed students are more likely to major in music and visual arts, while dyslexics often have superior performances in tasks for visuospatial discrimination and visual memory . FurtherA recent large meta-analysis shows that ADHD has a strong hereditary basis (Undeniably Leonardo accomplished more than any other human being could possibly dream of in a lifespan, but one wonders what would have been the impact of his work on history if he had managed to apply himself more consistently to his art and effectively disseminate his intuitions and discoveries.Besides the beauty of his art and the mesmerizing power of his observations, in the 500th anniversary of his death, Leonardo da Vinci should also be remembered for his resilience. The difficulties linked to his extraordinary wandering mind caused him deep regrets but did not prevent him from learning and exploring the wonders of human life and nature.