Attention-deficit hyperactivity disorder (ADHD) is one of the most common psychiatric neurodevelopmental disorders in children and adolescents. Although ADHD has been studied for nearly a century, the cause and pathophysiology of ADHD is yet largely unknown. However, findings from previous studies have resulted in the formation of a new hypothesis: Apart from the well-known multifactorial etiology of ADHD, recent evidence suggests that the interaction between genetic and environmental factors and especially Wnt- and mTOR-signaling pathways might have an important role in the pathophysiology of ADHD. The Wnt-signaling pathway is known to orchestrate cellular proliferation, polarity, and differentiation, and the mTOR pathway is involved in several significant processes of neurodevelopment and synaptic plasticity. As a result, dysregulations of these pathways in a time-dependent manner could lead to neurodevelopmental delays, resulting in ADHD phenotype. This review presents further evidence supporting our hypothesis by combining results from studies on ADHD and Wnt- or mTOR-signaling and the influence of genetics, methylphenidate treatment, Omega-3 supplementation, and stress. It is one of the most common psychiatric and behavioral disorders in children and adolescents with over 5% of the population affected worldwide and persists in about 60% of the cases into adulthood2. ADHD is often accompanied by comorbidities such as conduct or oppositional defiant disorder, major depressive disorder (MDD)3, obsessive-compulsive disorder (OCD)4, personality disorder5, autism spectrum disorder (ASD)6, and epilepsy7 among others. Further, ADHD has also been associated with an increased risk of obesity/overweight8. The burden that ADHD patients and their families face in daily life greatly affects their adult life. Moreover, according to a recent review, the global burden of developmental disorders including ADHD has not significantly improved since 19909.Attention-deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder characterized by inattentiveness, hyperactivity, and impulsivity11. ADHD has also been associated with polysubstance-dependency, early onset of addiction, and borderline personality disorder12. A substantial amount of negative impact on school performance and long-term academic outcomes has been found in patients with ADHD. Yet, adequate treatment is able to improve academic performances14. In addition, studies show that young people with ADHD were at a considerably higher risk of being involved in accidents15. ADHD diagnosis, in particular the combined type (hyperactive-impulsive subtype), was found to have an impact on reduced estimated life expectancy16. In addition, in adult ADHD, the assessed health-related quality of life, work productivity, and regular daily activities have been found to be impaired17.Emotional dysregulation has been found also to be very common in ADHD. It has been suggested to be a significant cause of impairment in the different aspects of ADHD patients’ life22. Particularly, a delay in cerebral cortex maturation predominantly in the frontal cortex has been noted in ADHD patients18. In a study combining magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), and resting-state functional MRI (fMRI) technique, alterations were found in the forceps minor, the internal capsule, the corona radiata, the splenium of the corpus callosum, and the bilateral basal ganglia of patients with ADHD23. DTI application revealed that in adults with a history of ADHD, maturation of white matter was delayed24. In a recent mega-analysis by the ENIGMA-ADHD consortium, subtle differences in cortical surface area were found in children, confirming the involvement of the frontal cortex in ADHD as well19.Alterations in brain structure, connectivity, and maturation processes in patients with ADHD have been reported25, however, no single gene alone may predict the disorder. On the contrary, several studies have indicated that a third of the heritability in ADHD is caused by the polygenic component that comprises several common variants each with small effect size26. Furthermore, a great deal of evidence supports the interaction between genetic (polygenic) and environmental factors during early development, in particular prenatal stress, leading to the neurobiological susceptibility to the disorder28.The heritability of ADHD is estimated between 77 and 88%29. Structural and functional neuroimaging analysis of ADHD brains suggests that psychostimulants  are associated with normalizing the aforementioned structural abnormalities seen in ADHD patients31.Regarding pharmacological treatment, first-line agents for ADHD are stimulants such as methylphenidate (MPH) or dexamphetamine32. The findings from previous studies compelled us into forming the following hypothesis: Apart from the already known multifactorial etiology of ADHD, recent evidence suggests that the interaction between genetic and environmental factors and especially Wnt- and mTOR-signaling pathways might have an important role in the pathophysiology of ADHD. In this narrative review of the literature, we will present the current evidence supporting this hypothesis linking genetic, stress, and Wnt/mTOR pathways with ADHD, as well as discuss the missing link that needs to be investigated.Although a wide range of studies has been performed to understand the underlying pathology of ADHD, the etiopathology of ADHD is still not fully understood. Elucidating the etiopathology of ADHD will help to expand the strategies to reduce symptoms, develop personalized therapy and predict response to medication therapy. New insights will additionally reveal potential biomarkers for improved differential and predictive diagnosis approaches33, but also processes involved in adult neurogenesis34. On the basis of their activity at the cellular level, Wnt-signaling has been classified into two categories, canonical and non-canonical35. In humans, 19 genes were identified to encode Wnt protein subtypes. Further, they activate several pathways by coupling with various receptors36. In the canonical Wnt-signaling pathway, Wnt ligands bind to a Frizzled (Fzd)/low-density lipoprotein receptor-related protein (LRP) complex at the cell membrane. This complex (Wnt/Fzd/LRP) recruits disheveled (Dvl), which in turn inhibits the pathway, leading to β-catenin degradation. Once the β-catenin degradation stops, it accumulates in the cytoplasm before translocating into the nucleus. Subsequently, there is an interaction between β-catenin and transcription factor (TCF)/lymphoid-enhancer factor (LEF) in the nucleus to regulate the transcription of target genes37. TCF/LEF target genes are known to regulate stem cell maintenance and differentiation along with cell proliferation38.The wingless-INT (Wnt)-signaling pathway is known to orchestrate cellular proliferation, polarity, and differentiation Fig. ; process39. It has also been described to be associated with neurodevelopmental disorders such as ASD40 and schizophrenia42. A component of the phosphatidylinositol 3-kinase (PI3K) cell survival pathway is the mTOR. It has a significant role in the regulation of cell growth and proliferation. mTOR operates at a key junction in the PI3K pathway. It further acts downstream and upstream of protein kinase Akt. mTOR also regulates the protein synthesis necessary for proliferation and cell growth by forming two multi-protein complexes, namely mTOR complex I (mTORC1) and mTOR complex II (mTORC2)43.The mammalian target of rapamycin (mTOR) pathway is involved in several significant processes of neurodevelopment and synaptic plasticity Fig. 39. It ha44. The second pathway involves the energy-sensing arm, which responds to low or insufficient ambient cellular ATP. AMPK is phosphorylated through the serine/threonine-protein kinase STK11 . This results in TSC2-mediated mTOR inhibition. LKB1 complex activity releases inhibition of mTOR when the ATP level are abundant45. In the third pathway, the amino acid sensor GAP activity toward rags (GATOR1) complex  regulates mTOR in response to changes in levels of amino acids. In other words, GATOR1 inhibits mTOR-signaling when the level of amino acids are low. GATOR1 inhibition of mTOR is released once the amino acid levels return to normal levels46.There are three main signaling pathways known to converge and regulate the mechanistic target of mTOR. First, the growth factor pathway comprised of PI3Ks, phosphoinositide-dependent kinase 1 (PDK1), and RAC-alpha serine/threonine-protein kinase (AKT1). AKT1 is activated by the phosphorylation of PDK1, which is triggered when PI3K is activated. mTOR is activated via GTP-binding protein Rheb (RHEB) when tuberous sclerosis complex (TSC2) gets phosphor-inhibited by AKT1. This results in the phosphorylation of eukaryotic translation initiation factor 4E-binding protein 1 (4E-BP1) or protein S6 kinase beta-1 (S6K1)47. mTOR has been suggested to regulate neuronal differentiation and dendritic maturation48. Canonical Wnt-signaling has a major role in neurogenesis. During early neurogenesis, it promotes self-renewal to maintain neural progenitors. However, during mid and late neurogenesis it induces the differentiation of progenitor cells34.Both signaling pathways are not only important for early normal brain development but also for neurogenesis in the adult brain48 have shown how abnormalities in the ubiquitin system, a major regulator of key signaling cascades including mTOR and Wnt, are linked to two common neurodevelopmental disorders: intellectual disability (ID) and ASD.Dysregulation of both pathways may lead to pathological brain developmental conditions. For example, Kasherman and colleagues49, no single genetic variation could be used for diagnosis or prediction of ADHD. Moreover, the consensus is that ADHD is considered polygenetic, supporting also the notion that it is not a clear-cut categorical disorder but rather the extreme end of the spectrum of a continuous behavioral trait26. Indeed, the polygenic risk score (PRS) analysis summarizing statistically all the SNP results from a large genome-wide association study (GWAS) has shown some promising results50. For example, ADHD-PRS was found to associate with symptoms of hyperactivity-impulsivity and to be mediated by white matter microstructure in brain regions that have been suggested to have a role in ADHD pathology52. In addition, ADHD-PRS was found to predict educational achievement53, to be linked with the severity of the clinical profile in those with high PRS54, and even to predict MPH response55. Although the etiology and pathways involved in ADHD cannot be revealed by using PRS only, this approach seems to be a powerful tool studying endophenotypes of the heterogeneous disorder.Although ADHD was found to be highly heritable53. In addition to the 12 loci that covered 16 genes involved in brain-related pathways such as synapse formation, neuronal developmental, and dopaminergic transmission, gene set analysis of the most significant genes revealed that the Wnt/catenin-signaling pathway is associated with ADHD 53. Further studies on gene variants of the Wnt pathway were reported in adult ADHD study using GWAS and extended pedigree linkage56. Here, the authors reported several genes to be associated with adult ADHD, as for example, the α-catenin (CTNNA2) which is known to be involved in Wnt-signaling and to have a role in the catenin–cadherin cell–adhesion complexes for synaptic transmission56. Similarly, Aebi and colleagues57, revealed a significant enrichment of the Wnt/β-catenin signaling in a subpopulation of ADHD patients with the oppositional defiant disorder (ODD) by running bioinformatics clustering of the GWAS results. In a study assessing personality disorders, adult ADHD and family-based childhood ADHD, Kv channel-interacting protein 4 (KCNIP4) gene, suggested to be part of a negative feedback loop in the Wnt/β-catenin pathway, was found to associate with ADHD58.In the recent Psychiatric Genomic Consortium (PGC)-ADHD meta-analysis of the GWAS results including over 20,000 cases and 35,000 controls, the first genome-wide significant loci were identified (12 loci)59 reported recently a shared contribution of common SNPs in childhood ADHD and persistent adults in a meta-analysis of databases from large cohorts of ADHD children and persistent ADHD adults. In this study, the researchers were able to identify nine loci, containing genes involved in brain development, associated with ADHD persistence into adulthood. A significant genetic correlation between ADHD in childhood and its persistent ADHD in adulthood was found, in which also childhood ADHD-PRSs were associated with persistent ADHD59. Lastly, though not significant after multiple testing corrections, in the pathway analysis of persistent ADHD adults, nominal significant association to the “reactome energy-dependent regulation of mTOR by LKB1/AMPK”, “biocarta mTOR pathway”, and “reactome mTORC1-mediated signaling” was found59.Interestingly, Rovira and colleaguesLRP5 and LRP6 gene variants in four Caucasian European populations, which was found to be further significant after meta-analysis with previous published results60. Additional evidence to the involvement of the Wnt-signaling in ADHD comes from a study by Wang and colleagues61 who demonstrated in ADHD patients a significant correlation between low gray matter volume and three miRNAs  that were found to be involved in the Wnt-signaling pathways. In a recent study, the genetic architecture of the human cerebral cortex revealed that common genetic variants are linked with surface area and thickness of these regions62. In particular, intriguing is that loci linked with surface area, which was found to be negatively correlated genetically with ADHD, clustered with genes involved in the Wnt-signaling pathways62 Indeed, all the above-mentioned results support the involvement of Wnt-signaling pathways in ADHD and its phenotypes at the genetic and the transcriptomic level.68, its acute and chronic effects are still unclear and of continuous concern70. However, no conclusive evidence supporting or dismissing short- and long-term negative effects of MPH has been reported up to this date.It is well-known that MPH is one of the first-line drugs for the treatment of ADHD but despite its relatively high effect sizes in ADHD children (0.8–1.0 for hyperactivity and 0.6–0.8 for attention deficit)71. Clinical studies using fMRI analysis report that MPH administration is able to attenuate ADHD-related impairment in cortical maturation and functionality in children and adolescents by increasing gray matter levels in their cortices74. Although in general, MPH acts as dopamine, norepinephrine, and at low-level serotonin transporter inhibitor in high-, middle and low-affinity manners, respectively, thus enhancing the levels and the biological effects of these monoamines in the synaptic cleft75, the exact molecular mechanisms (including the pathways affected by MPH) involved in this context remains elusive.In vivo evidences showed that this stimulant affects positively hippocampal neurogenesis in young rats and neuronal plasticity in the amygdala78, but also acts through a novel mechanism of action that supports neuronal cell maturation63.In vitro research has revealed that MPH influences cell proliferation and differentiation, regulating the activity of synthesizing and metabolizing enzymes responsible for balancing the monoamine concentration in the cells and the synaptic cleft79, our group has hypothesized that treatment with this drug could lead to these same effects in neural cell lines through the Wnt-signaling activation mechanism. This was hypothesized since it has a pivotal role in maintaining these cellular processes in several conditions, such as neurogenesis and differentiation in embryonic development and tissue homeostasis80. More specifically, we were able to demonstrate in neuronal cell lines  that MPH activates Wnt-signaling, which was not due to the dopamine transporter inhibition—the main known therapeutic mechanism of this drug—since selective dopamine transporter inhibitor GBR-12909 treatment demonstrated the opposite effects63. Using a Wnt-luciferase reporter assay in 3T3 mouse fibroblast cell lines, we could confirm, quantitatively, that MPH activates the Wnt-signaling63.In order to test the influence of MPH on neuronal cell maturation and its capability of stimulating neurogenesis and cortical maturation in in vivo models65. In addition, Oakes and collaborators81 found that β-catenin  levels in juvenile male mice were elevated after a low dose of chronic MPH treatment (1 mg/kg) and reduced after high dose chronic treatment (10 mg/kg) administrated by intraperitoneal injections. The initial increase in the concentration of these factors by lower doses was followed by increased proliferation and survival of hippocampal cells, indicating that they might act as mediators of these cellular processes81 , and neurofibromin (NF1)—were described to be implicated with neurological disorders such as ASD, epilepsy, and ADHD85.The concomitant pathway to Wnt, mTOR, was also implicated in ADHD pathophysiology given that the complex Akt/mTOR-signaling is implicated in cell survival, synaptic plasticity, and formation, neurogenesis, and memory consolidation86 reported that MPH alters the mTOR pathway at different levels by decreasing the activity of Akt and mTOR substrates after short term treatment and increasing them after long-term treatment, which might regulate the aforementioned neuronal processes according to time of treatment  are essential fatty acids for homeostasis acquired through diet and include eicosapentaenoic acid (EPA), alpha-linolenic acid (ALA), and docosahexaenoic acid (DHA), which are crucial for brain development88.Omega-3 long-chain polyunsaturated fatty acids  and increased cell survival as well as neurite outgrowth in neurons90. Similarly, EPA, as well as DHA treatment, promoted differentiation of induced pluripotent stem cells (iPSC)-derived astrocytes from MDD patients concomitantly with increased CREB activity91, also known to be regulated by the non-canonical Wnt-signaling.At the molecular level, it is known that n-3-PUFA treatment increased cellular proliferation and migration while inhibiting apoptosis92. In addition, Shi and colleagues92 have reported that these events were associated with the PI3K-signaling upregulation, which subsequently led to Akt activation and to an increased expression of β-catenin. These results point to a possible simultaneous activation and connection between mTOR- and Wnt-signaling pathways -induced neuro-injured mice and PC12 cells, n-3-PUFA in vitro. In this study by Descorbeth and colleagues93, DHA treatment (1–200 µM) protected Schwann cells from lipotoxicity-mediated cell death through the activation of the aforementioned pathways  gene, known to be involved in stress regulation (see details under in chapter Stress and ADHD), was upregulated following FD pointing to the beneficial effects of fish oil supplementation94  or with a customized fish oil-enriched diet (FD), genes involved in cellular growth and proliferation, cellular development, embryonic development, synaptic transmission, development of the brain, inflammatory response, and developmental disorders have been found to differential express following FDn94 Fig. . Moreoven-3-PUFA have been largely explored in several neurological diseases99. Evidence for alterations in n-3-PUFA blood levels in ADHD as well as lack of prenatal n-3-PUFA intake associated with the risk of ADHD has been reported. In addition, several clinical trials hint at the improvement of ADHD core symptoms after add-on n-3-PUFA treatment. Researchers have recently shown that children with ADHD tend to eat less Omega-3-enriched food (such as fish and seafood) in comparison to neurotypical individuals102. Indeed, according to a meta-analysis, child and adolescent ADHD patients have lower levels of DHA, EPA, and total n-3-PUFAs compared to controls103. However, the link between levels of n-3-PUFA and the occurrence of this disorder in childhood is not limited to postnatal exposure: Lopez-Vicente and colleagues104 have reported that an increase in the ratio between n-6 and n-3 concentrations in cord plasma during pregnancy may increase ADHD rates when children reach the age of seven. Some investigations have demonstrated that cognitive functions, such as working memory, teacher-rated behavior, and impulsivity, have improved after n-3-PUFA administration in children with ADHD109. In particular, EPA supplementation seems to elicit small but significant improvement in inattention and hyperactivity symptoms in ADHD patients111. An in vitro study has recently shown that PC12 dopaminergic cells had their viability significantly increased after n-3-PUFA administration112, starting with lower doses (from 100 pM). Interestingly, a double-blinded report revealed that a combined treatment of n-3-PUFA plus MPH in a group of ADHD children was able to increase the efficacy of MPH treatment by significantly increasing the response to this drug113. Similarly, Anand and colleagues114 found that n-3-PUFA could improve ADHD scores in atomoxetine-treated children in comparison to the group that received this drug only. However, the difference was not statistically significant in cases of inadequate dosage administration114.In addition, the nonpharmacological protective mechanisms of 97 have described that PUFA may modulate different signaling pathways in the brain by increasing the activity of adenylate cyclase and protein kinase A and thereby influencing serotonin, beta-adrenergic, and dopamine receptors.In addition, Liu and colleaguesn-3-PUFA, mTOR, and ADHD some evidence has been reported for n-3-PUFA and mTOR in other neuropsychiatric disorders. Based on mounting evidence proving that n-3-PUFA have beneficial effects on people affected by depression, schizophrenia, and bipolar disorder117 in combination with data on the correlation between mTOR and other pathologies , Shirooie and colleagues118 reviewed that mTOR can be one of n-3-PUFA’s targets to treat neurodegenerative diseases by regulating essential cellular processes such as apoptosis and autophagy. In addition, Giacobbe and colleagues119 have recently discussed the anti-inflammatory effect of n-3-PUFA within the context of neuropsychiatric disorders such as depression. This review mentions that intracerebroventricular injections of resolvins D1, D2, and E1 (n-3-PUFA metabolites) seem to attenuate depressive-like behavior in mice via activation of mTORC1-signaling pathway121. Therefore, n-3-PUFA might elicit its positive effects on ADHD via mTOR, however, this still needs to be investigated.Although, to date, no link was established between n-3-PUFA supplementation, and the occurrence of ADHD. Moreover, some results are controversial to the aforementioned positive studies about favorable aspects of n-3-PUFA supplementation123. Although overall results point to its beneficial effects mainly in mild ADHD subtypes124, making deeper and molecular approaches even more necessary.To date, there is a lack of evidence connecting Wnt and/or mTOR pathways, 126. Risk factors such as maternal life-events such as stress or trauma, alcohol consumption, and smoking during pregnancy put offspring at risk of developing ADHD129. However, the degree to which these are casual effects or due to unknown confounding factors is highly debated131. Recent studies suggested that risk factors, such as maternal substance use during pregnancy is associated with offspring ADHD, are not casual but rather confounding by other risk factors133.As mentioned previously, the susceptibility to ADHD is influenced by the interaction of polygenic and environmental factors. The impact of environmental risk factors increases especially during critical developmental stages in life. The pre- and perinatal periods are associated with high phenotypic plasticity and thereby represent such critical developmental episodes134. Moreover, the presence of depressive symptoms during pregnancy suggested inducing the early onset of ADHD symptoms in 3- to 6-year-old children135. Therefore, it is rather difficult to separate pre, peri-, and postnatal stress effects on the risk of ADHD, however the overall hypothesis of accumulating environmental factors including stress may exacerbate it.In terms of maternal influence on ADHD development, maternal ADHD symptomatology, also in mothers without ADHD diagnosis, may indirectly induce ADHD symptomatology in the offspring by negatively affecting the home environment136. Such stress may result directly from maternal cortisol levels, indirectly from maternal anxiety, depression, trauma, or even from the administration of synthetic glucocorticoids such as dexamethasone or betamethasone137. Glucocorticoids can influence intracellular signaling pathways as for example the Wnt-signaling pathways  with dexamethasone for example increases the expression of Dickkopf 1 (DKK1) and decreases the expression of canonical Wnt target genes139. To note, the Wnt-signaling is important for neurogenesis and its inhibition causes a defect in neural differentiation and proliferation, which might explain how stress affects neurodevelopment139. The neuronal and glial energetics hypothesis further describes a possible association between glucocorticoids and psychiatric neurodevelopmental disorders. Glucocorticoids inhibit glycogen synthesis as well as the supply of glucose to neurons and astrocytes140. As a result, the glial activity will be downregulated during stressful situations and will lead to fatigue and a predisposition for an inefficient and/or inconsistent behavioral performance140.In addition, socioeconomic factors seem to be an essential role in this context, since children whose mothers are from urban, low-income backgrounds and had been under psychological stress before and during pregnancy are more susceptible to develop ADHD142. The spontaneous hypertensive rat (SHR) is one of the most extensively studied animal models for ADHD143. Cognitive performance tests in SHR indicate an association between cognitive deficits, insulin resistance, and hypertension144, while Wnt-signaling has been shown to mediate insulin and blood pressure regulation and thereby suggests a possible relationship between Wnt-signaling and ADHD145.It has been confirmed in animal models that ADHD-like behavioral symptoms and changes in brain function can result from early life stress147. The hypothalamus–pituitary–adrenal axis (HPA axis) is an important responder to stressful environments. Several studies have shown that stress reactions are different in ADHD patients compared to healthy controls151. ADHD patients show reduced diurnal cortisol levels compared to healthy controls153. Cortisol levels can be decreased by mineralocorticoids- (MR) and glucocorticoids- (GR) receptors through a negative feedback system. GR and MR inhibit the synthesis and release of corticotropin-releasing factor in the hypothalamus and adrenocorticotrophic hormone in the pituitary gland154. The candidate gene FKBP5 is involved with the GR and its pathway156. It is an important regulator of the negative feedback system of the HPA axis by reducing the sensitivity of GR157. Stress hormones increase the expression of the FKBP5 resulting in reduced GR affinity and thereby increase cortisol levels. Polymorphisms on the FKBP5 gene have been found to be associated with ADHD156. Moreover, one of the polymorphisms was found to associate with low cortisol levels and ADHD. Therefore, FKBP5 might have an important role in linking Wnt-signaling, stress, and ADHD (Fig. ADHD symptoms are associated with higher perceived stress160 suggest that n-3-PUFAs improve stress-related neurobiological and behavioral changes via attenuation of the associated HPA-axis hyperactivity. The latter findings are suggestive that dietary n-3-PUFAs may modulate the often observed HPA-axis dysfunction associated with the development of some neuropsychiatric disorders including ADHD and MDD. Observational studies in humans further support a link between the HPA axis and PUFA metabolism, as cortisol decreases the production161 and increases the breakdown of PUFAs162.Preclinical studiesFrom the current review of the literature, we suggest the involvement of Wnt and mTOR pathways in the etiopathology of ADHD with a wide range of evidence, at the genetic, environmental, functional, and molecular as well as at the pharmacotherapeutic levels. Nevertheless, there is still a gap between the current knowledge and the lack of evidence in neuronal brain tissue originating from ADHD patients. This, of course, arises because brain tissue is not available since neither biopsies nor post-mortem samples are available.Based on the data presented so far, it is noticeable that genetic factors are relevant in understanding ADHD. Studying such genetic risk factors at the molecular level is as important as exploring the environmental factors that might have a role in the disorder. To illustrate this, we pointed out the possible involvement of pre-, peri-, and postnatal stress associated with ADHD also linking it to the genetic risk factors, possibly together affecting canonical Wnt-signaling, which in turn affects neurodevelopment. Unfortunately, there is still a shortcoming in understanding the role of stress on the molecular and cellular levels that needs to be elucidated.163. Therefore, there is an urgent need for a personalized neuronal model in a dish originating from individuals with ADHD that maintains their genetic background. Reprogramming human somatic cells into iPSCs and differentiating them into neural cells or brain organoids is a powerful technology that provides the essential means to study living human central nervous system cells for modeling complex disorders such as ADHD in a semi ex vivo manner164. Such personalized models may provide a platform to test such a hypothesis, enabling the measures of molecular and functional effects of genetic and environmental factors on neurodevelopment processes.Studying the pathomechanism in human cells is limited because the relevant tissue, the brain, is not accessible by biopsy and ADHD post-mortem samples are scarcely available for research purposes. Although animal models are a valuable alternative in studying ADHD, they are not able to mimic the polygenic profile of a patient165. Following the aforementioned observations, it would be of utmost importance to test the hypothesis of Wnt- and mTOR-pathway alterations and stress effects at the cellular level in developing neural cells from ADHD patients compared to healthy controls. As discussed previously, the novel technique of using iPSCs to establish a personalized model of ADHD seems to be a novel platform to deeply understand the mechanism of ADHD, which will also provide scope for drug testing. Overall, it would be an important step forward to form not only effective treatment for ADHD but also for the development of preventive approaches.In conclusion, both pathways may be associated with ADHD at the genetic and environmental level linking both susceptible risk genes with stress. Indeed, Wnt-/mTOR-signaling and stress were linked with many other neurodevelopmental and neurodegenerative disorders as reviewed above. This does not contradict to the fact that many of these disorders are comorbid as well as share some phenotypes, e.g., cognition, which might explain the common mechanisms. However, the polygenic combination, the time point of alterations, and the time point of stress might cause to the different trajectories leading to the disorder, as reviewed by Sullivan and colleagues


ADHD is a common neurodevelopmental disorder with onset of symptoms typically in early childhood. First signs of the disorder, including language delay, motor delay and temperament characteristics, may be evident as early as infancy. The present review describes published evidence about early motor signs of either children with later symptoms of ADHD or a later diagnosis of the disorder. Nine published cohort studies were included after a systematic search of related terms in PubMed and PsycInfo databases. Study eligibility criteria included: (1) report on early motor function or any motor-related signs; (2) the presence of a participants’ assessment by/at 12 months of age; (3) report of a later presence of ADHD symptoms. The limited number of reports included suggests an association between mild early neurological markers and later developmental coordination disorder and motor overflow movements. Unfortunately, due to their small sample sizes and focus on group reports rather than individuals, they have limited power to find strong associations. Early motor indicators of ADHD, if present, appear to be non-specific, and therefore not yet useful in clinical screening. Spontaneous motility seems to be a promising measure for early ADHD detection, although further studies with large cohorts are recommended to determine its clinical role in children at risk for ADHD. ADHD is a common neurodevelopmental disorder with symptoms typically emerging during early school years and a worldwide prevalence estimated between 5 and 7% , 2. ADHDInvestigating early motor signs during the first year of life could be of high importance for the study of early biomarkers of common neurodevelopmental disorders, such as ADHD and ASD, which may share neurobiological underpinnings –21. TherThe neurobiological basis for the primary theory is that delays in brain maturation are associated with delays in motor development and specific motor skills  in the AThe second theory—of the comorbidity between ADHD and DCD as the potential cause of motor delays—is also supported by neurological findings. Although the comorbidity of ADHD and DCD is not often taken into account, a high percentage of children with ADHD 30–50%) experiences co-occurring DCD with a familial correlation of 0.38 –31. Almo–50% expeCerebellar abnormalities in children with DCD could also explain postural control and balance problems. Children with ADHD without co-occurring DCD have shown fine motor fluency and flexibility, but when a co-occurring DCD condition is present, fine motor difficulties are observed . HoweverSince ADHD symptoms usually emerge during the early school years, both clinical and neurobiological research have focused on school-aged children, adolescents and adults. Interest in early signs of ADHD is, however, rapidly growing. Recent studies report initial evidence of some indicators appearing prior to school-age, including difficult temperament, and language and motor delay , 39. StiTo shed light on early motor signs in ADHD and their emergence, we systematically reviewed the publications investigating motor behavior during the first year of life in infants who later develop subclinical ADHD symptoms or are diagnosed with the disorder.A systematic literature search was performed in PubMed and PsycInfo databases including the following keywords: (1) “ADHD” OR “Attention deficit hyperactivity disorder” OR “Attention deficit-hyperactivity disorder”; (2) AND “infant*” OR “infancy” OR “neonatal” OR “newborn” OR “baby”; AND “movement*” OR “motor” OR “sensory-motor” OR “sensori-motor” OR “motion”. A systematic review of the references of the included papers was also performed to ensure a thorough search. The first search was performed in July 2016, and once more in January 2017, which yielded one additional relevant article.Study eligibility criteria included: (1) report on early motor function or any motor-related signs; (2) the presence of a participants’ assessment by/at 12 months of age; (3) report of a later presence of ADHD symptoms. The first selection was based on the study titles, as identified by one of the authors (AA). Second, abstracts were independently screened for eligibility by two authors (AA and OC). Two authors (AA and OC) independently performed the data extraction and discussed their findings to reach a consensus. Full texts of potentially relevant papers were read to ascertain whether the study met all selection criteria.The following data were extracted from the included articles: type of study , source population , participants’ age range, type and timing of early motor signs, type and timing of ADHD diagnosis (based on the DSM-5) , or ADHDQuality ratings were conducted using a modified Methodological Quality Checklist  developeIn total, 417 articles were identified via the database search on both PubMed and PsycInfo; 30 studies were selected for review. Nine articles were included after completing the selection process .Another large study by Lemcke et al.  includedSimilarly, Jaspers et al.  studied n = 14).Two studies explored motor signs at 12 months of age. Johnson et al.  studied Lastly, motor signs of extremely low birth weight and very preterm infants were evaluated at 12 months with the Neurosensory Motor Developmental Assessment (NSMDA) and these scores were examined together with clinical and psychometric measures of attention at 7–9 years of age . At 12 mADHD is a neurodevelopmental disorder characterized by a pattern of inattention and/or impulsivity and hyperactivity across different contexts. Since early identification of ADHD is essential to optimize the quality of life, there is growing research interest in the investigation of early clinical and behavioral features of children later diagnosed with ADHD. To further investigate this topic, we reviewed the literature summarizing the full spectrum of motor impairments which might be potential early indicators of ADHD. In particular, we included studies which report motor skills of infants during the first year of life who subsequently (1) received a formal psychiatric diagnosis of ADHD based on DSM-IV or the ICD-10, or (2) whose behaviors were related to high levels of ADHD symptoms, as identified by questionnaires.Four of nine studies presented included a formal diagnosis of ADHD through a psychiatric assessment , 47, 48.The first detectable abnormalities of motor development, GMs, in children later diagnosed with ADHD seem to be associated more strongly with ADHD when it is co-occurring with other psychiatric disorders than with ADHD alone. This is consistent with previous reports suggesting that ADHD with a co-occurring disorder is a probably more severe form of ADHD , 61. IndDuring the time of spontaneous motility (0–5 months) and beyond, at least up to 9 months, a delay in gross motor function was significantly more common in infants who later developed ADHD. At 3 and 9 months, Gurevitz et al.  reportedAuerbach et al. , examiniOverall, these results support the hypothesis of a link between mild neurological markers and developmental coordination disorder, and motor overflow movements, all of which are more common in children with ADHD . NeverthResults are more inconsistent when it comes to the relationship between early motor signs and later subclinical ADHD symptoms. Some reports state that early spontaneous motility is correlated with attention problems, including less motoric maturity at 7 days of life in children who are later hyperactive in kindergarten. Similarly, Jeyaseelan et al.  found a There are multiple possible reasons for these inconsistent findings. The populations that were studied are extremely heterogeneous and have different degrees of risk for ADHD, from infants with clinical signs of early hyperactivity to those who are born preterm or were small for gestational age. The assessments used to test the presence and characteristics of early motor signs were also heterogeneous, including parental questionnaires, qualitative and quantitative assessments of motor behavior, and early attentional measures. Finally, the diagnostic instruments that were used to evaluate later presence of ADHD symptoms differed among studies, making comparisons very challenging.The limitation of our review is that the studies which are included have small sample sizes and focus on group reports rather than individuals, so they have limited power to find strong associations. Although the studies are of high quality according to the rating scheme, the outcome measures have questionable accuracy (see Table In summary, there are a limited number of reports investigating gross motor function in the first year of life in children who later have ADHD symptoms or are diagnosed with ADHD. Early detection of ADHD-related motor abnormalities would be important to provide a timely diagnosis, and most importantly, early intervention, especially in case of a very strong association between ADHD and early motor signs. This would assist clinicians in the continuous development and implementation of interventions at a very critical period of child development, when the brain is rapidly developing and neuroplasticity is highest. Unfortunately, data emerging from this review show that early motor signs, if present, seem to be non-specific, and therefore not yet worth implementing in clinical screening protocols. Some qualities of spontaneous motility seem promising as an early detection tool for risk of ADHD, although further studies based on the individual, with larger cohorts and more specific and semi-quantitative scoring systems, are necessary to determine their clinical role in populations at risk for ADHD.


Adult attention-deficit hyperactivity disorder (ADHD) has recently attracted much attention, however, an up-to-date estimation on the prevalence of adult ADHD is lacking. In this study, we aimed to assess the global prevalence of adult ADHD in the general population through a systematic review and meta-analysis.PubMed, Medline, Embase and PsycINFO were searched to identify relevant articles published from January 2000 onwards. Population-based studies that were conducted in the general adult population and quantified the prevalence of adult ADHD were included.The prevalence of persistent adult ADHD (with a childhood onset) and symptomatic adult ADHD (regardless of a childhood onset) both decreased with advancing age. By adjusting for the global demographic structure in 2020, the prevalence of persistent adult ADHD was 2.58% and that of symptomatic adult ADHD was 6.76%, translating to 139.84 million and 366.33 million affected adults in 2020 globally.This study provides an up-to-date estimation of the global prevalence of both persistent and symptomatic adult ADHD. A well-defined strategy for diagnosing adult ADHD and large-scale investigations on the epidemiology of adult ADHD are needed. Attention-deficit hyperactivity disorder (ADHD), a clinically heterogeneous neurodevelopmental syndrome that comprises developmentally inappropriate inattentiveness, hyperactivity and increased impulsivity, is the most common psychiatric disorder in childhood . ADHD siADHD has long been conceptualised as a disorder of childhood that gradually diminishes with advancing age during adolescence and young adulthood. However, this assumption was challenged by follow-up studies that observed the persistence of ADHD from childhood into adulthood . DespiteGlobally, it has been estimated that approximately 5% of children and adolescents are affected by ADHD . CompareIn this study, we conducted a systematic review of epidemiological studies that reported the prevalence of adult ADHD in the general population. Our objectives were to 1) assess the global prevalence of adult ADHD; 2) explore the potential associated factors of adult ADHD; 3) estimate the global number of people affected by adult ADHD in 2020.We conducted this systematic review and meta-analysis in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines . The revOn 2 December 2019, two researchers (MZ and QY) independently searched PubMed, Medline, Embase and PsycINFO to identify relevant articles published from 1 January 2000 onwards, that reported the prevalence of adult ADHD in the general population. Search terms related to ADHD (“attention deficit hyperactivity disorder” or “ADHD”), adult (“adult” or “adulthood”), and prevalence  were combined, and the full details of the search strategy are in Table S1 in the Two researchers (MZ and QY) independently screened titles and abstracts of all retrieved records by literature searches and then reviewed the full-texts of potentially eligible publications. To be included, eligible studies should be primary investigations that were conducted in an adult sample (≥18 years of age). Numerical prevalence estimates of adult ADHD should have been provided, and the definitions and diagnostic approaches of adult ADHD should have been explicitly addressed. Multiple publications from the same investigation were carefully compared, and the one with the largest sample size or the most comprehensive results was kept. Studies that were confined to a subset of adult population with comorbid disorders  or in specific settings  were excluded. No language restrictions were applied. Disagreements were resolved by group discussions with a third senior researcher (PS).From 12 March 2020 to 15 April 2020, the same two researchers (MZ and QY) independently extracted data using a predefined data collection form. Author, year of publication, title, study location, country, region , year of investigation, study design, sampling strategy, study sample size, age range and female proportion of sample, diagnostic criteria of adult ADHD, and the reported prevalence of adult ADHD (numbers of sample and cases). Where possible, the prevalence rates of adult ADHD were respectively extracted by age group and sex. For articles where the year of investigation was not provided, the mean time lag between investigation and publication  statement . The STRAs indicated in the previous two systematic reviews of adult ADHD, the definitions of adult ADHD in epidemiological studies varied significantly. Not all the included studies in those meta-analyses required a childhood-onset to define adult ADHD ,16. Give2I statistic with ≥50% and the Cochran's Q statistic with a P < 0.05 to indicate a significant degree of heterogeneity between studies [We used a Mantel-Haenszel random-effects meta-analysis to generate the pooled prevalence of persistent adult ADHD and symptomatic adult ADHD. The variance of raw prevalence from all studies was stabilised by using the Freeman-Tukey double arcsine transformation . We used studies ,21. To e studies -24.Sources of heterogeneity were explored by subgroup meta-analyses for persistent adult ADHD and symptomatic adult ADHD respectively, according to diagnostic tool, DSM version , sex , setting , investigation period , WHO region  and WB region . As a rule, three and more studies should be available for each subgroup to stabilise the heterogeneity test statistic.iu) was added into the model:Multiple data points were provided within a single study, based on which we established the prevalence of adult ADHD as a function of age. To control the effects of multiple data points from the same study and the same country, a random effect .Literature database searches identified 2346 records. After removal of duplicates, 1085 records were screened by title and abstract, resulting in 164 potentially eligible articles for full-text review. Finally, 40 unique articles, covering 30 countries, were included in this systematic review and meta-analysis, among which 20 reported prevalence data on symptomatic adult ADHD, 19 on persistent adult ADHD, and one on both  of the 40 articles were published in the last decade (2010-2019), conducted in urban and rural mixed settings , or with a quality score of six or above . In addition, more than half of the included articles reported the sex-specific prevalence , were with a sample size of >1000 , or were conducted in HICs . Moreover, almost half of the 40 articles provided age-specific prevalence of adult ADHD , or were conducted in EUR .2I = 98.8%; P < 0.001). By removing a single data point at one time in the sensitivity analysis, the pooled prevalence ranged from 4.22% (95% CI = 3.26-5.29) to 4.88% (95% CI = 3.69-6.22), and no studies were identified as potential outliers. The Egger's test provided evidence of small studies effect (P = 0.01) . According to the leave-one-out sensitivity analysis, the pooled prevalence varied from 8.25% (95% CI = 6.75-9.88) to 9.19% (95% CI = 7.52-10.99), no single study significantly influenced the overall pooled prevalence. Potential publication bias was suggested by funnel plot, Egger's test and Begg's test, respectively  form 21 included articles involving 50 098 individuals. The between-study heterogeneity was also high (I2 = 97.6%; The relation between age and adult ADHD prevalence was established using multi-level mixed-effects meta-regression (To the best of our knowledge, this systematic review and meta-analysis comprehensively describes the global prevalence of both persistent and symptomatic adult ADHD in the general population based on data published from 2005 to 2019. Our analyses show that the pooled prevalence of persistent adult ADHD was relatively higher in LMICs than in HICs and that of symptomatic adult ADHD varied across WHO regions. We revealed that the prevalence of both persistent and symptomatic adult ADHD decreased as age increased. In 2020, the prevalence of persistent adult ADHD was 2.58%, and that of symptomatic adult ADHD was 6.76%, equivalent to 139.84 million and 366.33 million affected cases globally.As expected, high levels of heterogeneity of the included studies were noted. Several possible reasons might have contributed to this phenomenon. First, the age of interviewed participants in the included studies was not unified, ranging from young adults to the elderly. Given the fact that the prevalence of adult ADHD decreases with advancing age, as revealed in previous investigations and our meta-regression, it is not surprising to observe such a diversity in the reported prevalence ,26. SecoOur study distinguishes itself from the abovementioned two systematic reviews by its separate analyses for persistent adult ADHD and symptomatic adult ADHD. Although ADHD has been traditionally under the umbrella of neurodevelopmental disorder, recent evidence has demonstrated that ADHD does not necessarily begin in childhood -9. HoldiA number of limitations need to be considered in interpreting the results in our study. First, the included studies used different diagnostic criteria and case definitions, were conducted with various study designs, sampling methods and in different study populations, which might have affected the estimated pooled prevalence of both persistent and symptomatic adult ADHD in the present study. Second, the considerable heterogeneity across included studies could not be fully ruled out by a priori selected variables, including diagnostic tool, DSM version, sex, setting, investigation period, WHO region, and WB region. The effects of other potential correlates of adult ADHD, such as ethnicity, were not able to be addressed due to the lack of sufficient information. Third, publication bias might also be a source of heterogeneity, but we did not try to eliminate publication bias in our analyses, because we deemed that an observed prevalence of adult ADHD that substantially differed from previous estimates was likely to have been published.The lack of internationally acknowledged diagnosis would lead to altered prevalence estimates of adult ADHD across the world. The famous WMHS has investigated the prevalence of DSM-IV-based persistent adult ADHD across 20 countries, while the introduction of DSM-V might lead to a further increase by bringing a rise of age-of-onset from seven years to 12 years and switching the diagnostic emphasis from clinically significant impairments to more lenient symptoms ,30. WellTo conclude, this study reveals that the prevalence of persistent adult ADHD from childhood and that of symptomatic adult ADHD were 2.58% and 6.76% in 2020, representing considerable public health burdens worldwide. Both persistent and symptomatic adult ADHD became less common with advancing age. Development of a universal diagnostic strategy to detect adult ADHD symptoms is greatly needed for both clinical and public health purposes. Large-scale epidemiological investigations with high quality are called for to address the magnitude of adult ADHD across the whole globe.


Enterobacterales are widely distributed in the gastro-intestinal system of animals and may cause opportunistic infections. Worse still, multidrug-resistant Enterobacterales also poses a serious threat to public health. Tn7-like transposons have been found in several species of the Enterobacterales order and play an important role in dissemination of antibiotic resistance. This study aimed to investigate the distribution and genetic characterization of Tn7-like transposons in Enterobacterales isolates from food animals and their association with antibiotic resistance. Enterobacterales isolated from the samples were identified and classified according to the 16S rDNA sequence. Tn7-like transposons and associated integrons were detected by polymerase chain reaction (PCR) and sequencing. The antibiotic resistance of each Tn7-like transposon positive isolate was detected according to the Kirby-Bauer disk diffusion method. Then, six representative strains were selected to study the genetic environment by whole-genome sequencing (WGS). In total, we isolated 377 Tn7-like transposons positive strains of Enterobacterales. Class 2 integrons were detected in 99.5% of the isolates, and there were high frequency mutation sites especially in base 535, a stop mutation. Many isolates (54.9%) were multidrug-resistant and observed high resistance rates to trimethoprim/sulfamethoxazole and streptomycin. Among these strains, we found three new types of Tn7-like transposons, named Tn6813, Tn6814, and Tn6765. This is the first comprehensive survey that shows Tn7-like transposons in Enterobacterales from animals used for food production in different regions of China. This study also provides an insight into the horizontal transfer of resistance genes associated with Tn7-like transposons. Enterobacterales are widely distributed in humans and other animals  in medicine , and themedicine .Enterobacterales is mediated by transposons. Tn7-like transposons, as the Tn7 transposon derivatives, have been found in several species of the Enterobacterales order, such as Proteus mirabilis and Morganella morganii . Genome assembly was carried out by de novo assembly with Unicycler v0.4.7, and the sequence was annotated using the NCBI Prokaryotic Genome Annotation Pipeline v4.2. Mobile elements, resistance genes, and other features were annotated by INTEGRALL  plates containing 300 μg/ml rifampicin and 10.24 μg/ml flufenicol. Successful horizontal transfer of plasmid p1.1.2 containing Tn7-like transposon was confirmed using antibiotic sensitivity test and PCR, and then, the conjugation frequency was calculated as transconjugants divided by number of donors . All statistical analyses were conducted with the GraphPad Prism 8 software. Chi square test for samples were used. Value of 7-like transposons, Tn6763 (MN641830), Tn6764 (MN628641), Tn6817 (MT469878), Tn6813 (MT469876), Tn6814 (MT469877), and Tn6765 (MT503200), identified in the present study were submitted to NCBI GenBank.The complete sequences of p1.1.1 (CP047113), p1.1.2 (CP047114), and all TnEnterobacterales were isolated through analysis of samples collected from Sichuan, Hainan, Chongqing, Shandong, Hebei, Xizang, Liaoning, and Anhui provinces. Of the 1,474 Enterobacterales strains examined, 377 strains contained Tn7-like transposons. They included 128 (24.0%) E. coli, 150 (57.5%) Proteus spp., 48 (22.9%) Providencia spp., 21 (14.4%) Morganella morganii, 17 (10.3%) Klebsiella pneumoniae, and 13 (8.2%) Salmonella enterica. Statistical analysis showed that the prevalence of Tn7-like transposons was different among different bacteria genera . The Tn7-like transposons positive rate of Proteus spp. was significantly higher than other bacteria’s  and trimethoprim/sulfamethoxazole (74.0%), followed by the rates for florfenicol (60.5%), gentamicin (24.4%), and ciprofloxacin (22%). Among them, resistance rates to gentamicin and ciprofloxacin were higher in Proteus spp. (30.7 and 28.0%) and S. enterica (38.5 and 23.1%). Low resistance rates to amikacin (6.1%), ceftazidime (5.8%), cefoxitin (5.8%), and aztreonam (4.2%) were detected, whereas S. enterica was more resistant than other Enterobacterales strains to ceftazidime and aztreonam (38.5 and 46.2%). Resistance to imipenem (1.6%) was only observed in E. coli, and most of the Enterobacterales isolates were highly susceptible to imipenem  were multi-drug resistant . imipenem . No signimipenem .Enterobacterales strains was 99.5% (two strains of E. coli lacked intI2). Through sequencing and sequence comparison, the results showed that intI2 usually had mutation sites, and most of them were at position 349, 372, 379, 535, 617, 767, and 774, among which 535 base mutations (C mutated to T) were terminating mutations , Tn6764 (GenBank accession number MN628641), and Tn6817 (GenBank accession number MT469878) were located on the chromosomes of P. mirabilis, E. coli, and S. enterica, respectively. They were typical Tn7 transposons comprising the transposition module , three gene cassettes , and an inactive class 2 integrase gene  and Tn6814 (GenBank accession number MT469877) were novel Tn7-like transposons in chromosomes, acquired from E. coli SFE8 and SCZE5, respectively. Tn6813 was 32,688 bp in size and Tn6814 was 32,874 bp. The structures of the two Tn7-like transposons were respectively surrounded by two IS1 elements, while one IS1 of Tn6813 was incomplete with missing C-terminus. Transposition module  of Tn7 in Tn6814 was intact, but tnsD in Tn6813 was truncated by an IS26 element. Compared to canonical Tn7, the area’s downstream of transposition modules of Tn6813 and Tn6814 differed by deletions involving class 2 integrons and its associated gene cassettes. Actually, Tn6813 had no intI2 and no gene cassettes (dfrA1-sat2-aadA1), and Tn6814 had only an aadA1 and an incomplete sat2 gene left (Tnene left .6765 (GenBank accession number MT503200) was located on a plasmid of P. mirabilis SCBX1.1, named p1.1.2 (GenBank accession number CP047114). Sequence analysis showed that 19 resistance genes, except cfr and erm(B), were carried by the Tn7-like transposon , qnrA1 (fluoroquinolone), aac(6’)-Ib-cr (fluoroquinolone and aminoglycosides), floR (chloramphenicol/florfenicol), mphE and msrE (macrolide), and lunF (lincosamide) genes. However, the cfr and erm(B) gene was carried by another 12,795 bp plasmid p1.1.1  with an average GC content of 52.94% that differed from that of the rest of the P. mirabilis plasmid . It had partial characteristics of the Tn7 transposon, which contained transposase genes tnsA, tnsB, and tnsC. But its transposition module lost tnsE gene and the tnsD was truncated by insertion of the inverted repeat (IR mcp) of Tn1721 , which also carried the Tn7-like transposon published in NCBI database (The plasmid carrying Tndatabase .E. coli EC600 (7-like transposon (Tn6765) transconjugant was obtained through the conjugative transfer test and at a frequency of 1.5 × 10−4 transconjugants per donor (average of three independent determinations). The stability of Tn6765, Tn6813, and Tn6814 was determined by picking 100 clones in the twenty first passage to detect the presence of Tn6765, Tn6813, and Tn6814, respectively. The results of all PCRs were positive, meaning that Tn6765, Tn6813, and Tn6814 can be stably inherited in the bacteria.Double-antibiotics Salmonella Shigella agar plates (300 μg/ml rifampicin + 10.24 μg/ml flufenicol) were used to screen the transconjugant. The results of drug sensitivity, electrophoresis, and sequencing showed that the plasmid p1.1.2 could be successfully transferred to li EC600 . A novel7-like transposons are important mobile elements to transfer bacterial AMR. Compared with information obtained from studies about the transposition mechanism of the Tn7-like transposons, available data on the comprehensive analysis of Tn7-like transposons in Enterobacterales isolates are still inadequate. Herein, we determined the incidence of Tn7-like transposons in Enterobacterales isolates obtained from several farms of chicken and swine raised for meat purpose. Among the 1,474 Enterobacterales isolates, 377 strains that carry Tn7-like transposons were identified. In different genus of bacteria, the separation rate of Tn7-like transposons was different  was significantly higher than other bacteria’s . This finding was consistent with previous reports that genomes of Proteus spp. exhibited strong plasticity facilitating high-frequency insertion of mobile genetic elements like Tn7-like transposons  and S. enterica (61.5%) strains may be due to the prevalence of multiple mobile elements in both bacteria, which was confirmed in previous studies (7-like transposons were likely to occur simultaneously with other mobile elements. High resistance to streptomycin (87.8%) and trimethoprim/sulfamethoxazole (74.0%) can be attributed to the intI2-associated resistance gene cassette  carried by Tn7-like transposons (intI2 contained the aminoglycoside adenyltransferase (aadA1 and aadA2), dihydrofolate reductase (dfrA1), and streptothricin acetyltransferase (sat2) encoding genes, which are responsible for streptomycin-spectinomycin, trimethoprim, and streptothricin resistance, respectively  were terminating mutations , gentamicin (24.4%), and ciprofloxacin (22%) were detected in the Tnpractice . Obviousollution .7-like transposons genetic structures were identified by WGS analysis, which showed that they included three typical Tn7 transposons  and three novel Tn7-like transposons . The IS26 segment in Tn6814 showed high level homology to the segment characterized in E. coli plasmid pV408 (GenBank accession number LN735560), and it harbored different mobile genetic elements (complete or truncated) and two resistance genes (blaCTX-M-65 and fosA3). The blaCTX-M-65-containing segment (IS26-fipA-IS1380-blaCTX-M-65-IS903B) in Tn6814 also showed nucleotide identity to the corresponding genetic structure that habored blaCTX-M-65 gene in Tn6813, with the exception of one IS26 sequence replaced by IS903B sequence in Tn6814 -IV and aph(4)-Ia] and florfenicol (floR). Diverse mobile genetic elements in Tn6814 included four intact ISs  and one incomplete IS1380, while six intact ISs  and five incomplete elements  were inserted in Tn6813 (7-like transposons was prompted by the ISs-mediated homologous recombination.Another resistance region bounded by ISn Tn6813 . From th6765 was highly homologous with Tn6450 (GenBank accession number MF805806), which was located on the chromosome detected by 6765 had a hypotheical protein gene before blaDHA-1; (ii) an HypA gene was inserted between ampR and qacE1 in Tn6765; (iii) an incomplete aminoglycoside N(3)-acetyltransferase encoding gene was inserted between ISEc59 and aph(4)-Ia; and (iv) Tn6450 was inserted downstream of the glmS gene, encoding glucosamine 6-phosphate synthase and surrounded by 5-bp direct repeats (CCAAT), whereas Tn6765 was located on the plasmid, there is no glms gene and repeated sequences at both ends  harbors a genetic structure, showing homology to the cfr segment characterized in P. cibarius G11 (Genebank accession number CP047287), which is partially differ from the existence of IS26-cfr-▵Tn554 tnpB-▵Tn3 family tnpA-IS26 section in another Tn7-like transposon, Tn6451  experiments, the Tnin, TnsC . This coin, TnsC , 2001a. 7-like transposons, we can speculate that the multidrug-resistant Tn7-like transposons have a certain evolutionary relationship, which has contributed to Tn7-like transposons playing a vital role in the field of storing resistance genes. Although the assembly was original, each of these Tn7-like transposons, or parts thereof, was identical to those found in other plasmids or chromosomes. This was related to the fact that Tn7-like transposons can transfer between strains and accumulate genetic material via mobile genetic elements.By comparing the genetic structure of different Tn7-like transposons in Enterobacterales isolates from livestock and poultry in China, and it presented detailed genetic characterization of three novel Tn7-like transposons Tn6765, Tn6813, and Tn6814, which were integrated into plasmids or chromosomes from E. coli and P. mirabilis. Multiple antibiotic resistance genes in Tn7-like transposons, considering that they were found in chicken and swine, are highly worrisome and may become a serious threat by spreading in other nearby animals, humans, and the environment. Therefore, robust measures should be taken to control the spread and emergence of mobile genetic resistance determinants in animals used for food production in China and the world, and our study provides an important reference for this.This study is the first report to comprehensively analyze the incidence and antibiotic resistance characteristics of TnThe datasets presented in this study can be found in online repositories. The names of the repository/repositories and accession number(s) can be found in the article/The animal study was reviewed and approved by College of Life Science, Sichuan University affiliation ethics committee, and all efforts were made to minimize animal suffering.All authors listed, have made substantial, direct and intellectual contribution to the work, and approved it for publication. JH conceived the study and drafted the manuscript. JH and CL collected samples and conducted data statistics. JH, CL, and PC performed experiments. HW supervised the research.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.


The prevalence of attention-deficit/hyperactivity disorder (ADHD) symptoms has been scarcely studied in indigenous cultures that preserve ancestral cultural characteristics. The objective of the study is to estimate the prevalence of suggestive diagnosis of ADHD among indigenous children and adolescents from villages in the Amazon. This is an analytical cross-sectional study using instruments to track ADHD symptoms (the Child Behaviour Checklist for ages 6–18: CBCL/6–18 and the teacher report form for ages 6–18: TRF/6–18) and to investigate their negative impact on the patients (using the Strengths and Difficulties Questionnaire—SDQ). The prevalence of a suggestive ADHD diagnosis according to the CBCL/TRF DSM-IV ADHD subscale without and with negative impact as assessed by the SDQ was 4.3% and 1.1%, respectively. Comorbid oppositional-defiant, conduct problems and anxious symptoms were present in all cases screening positive for ADHD. We also presented a case report as an illustration of the observed clinical presentation. ADHD is a recognizable disorder even in a culture that preserves millennial characteristics. Furthermore, the presence of ADHD symptoms was associated with significant impairment. Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder, characterized by the presence of inattentive and/or hyperactive/impulsive symptoms disproportionate to the developmental stage, causing functional impairment in more than one environment , 2. It aDespite having a well-established diagnosis and treatment, there are still discussions about its cross-cultural validity , 7. It iDespite the relevance, none of these studies evaluated indigenous villages, with preserved millennial old cultural characteristics. To fill this gap, we investigated the prevalence of ADHD symptoms in a population of indigenous village children and adolescents. We hypothesized that the frequency of ADHD symptoms would be similar to that of other epidemiological studies, reinforcing the notion that ADHD does not result from cultural factors.This was a cross-sectional and analytical epidemiological study.Initially, we obtained the approval of the Research Ethics Committee of the Medical School at the Federal University of Goiás. Later we had authorization from the National Commission for Ethics in Research from the National Health Council of the Brazilian Ministry of Health. Finally, we obtained permission from the National Indian Foundation of the Ministry of Justice of Brazil (FUNAI/MJ). These steps followed detailed clarifications on the research project and consent of indigenous leaders. The entire process to obtain the ethical and legal releases for this study took 2 years.2 and is located in the Araguaia River, a tributary of the Amazon Basin. They preserve their culture, passed down by their ancestors from almost 10,000 years ago. The Karajá is one of the 305 indigenous ethnic groups in Brazil. They are bilingual, speaking the native Karajá language and Portuguese, the official Brazilian language.The population of indigenous children and adolescents studied belongs to the Karajá ethnic group and lives on the largest fluvial island on the planet. Bananal Island is 20,000 kmAccording to the 2007 census carried out by the National Health Foundation, the total indigenous population of this ethnic group was 2486. Of these, 1905 lived in the four villages participating in the current research. The number of individuals from 7 to 14 years of age was 450 (242 boys and 208 girls). The initial sample size calculated to assess the prevalence of ADHD in this population was 219, but at the end, 186 subjects participated in the study  to assess the mental health of children and adolescents, it is essential that at least two sources of information be researched (family and school). The Karajá children only start school at the age of 7 so younger children could not be included; (2) at the age of 14–15, the boys of this ethnic group participate in the ritual of passage to adult life, called The subjects were chosen systematically, according to the list of names on the spread sheet of the 2007 population census: one participant was chosen and then the next  until the stipulated number for the age group, sex and village was reached. The selected participant was excluded if the parents or guardians did not sign the informed consent form.As presented in Table Forty teachers (25 indigenous and 15 non-indigenous) participated, including ten women (8 indigenous and 2 non-indigenous) and 30 men (17 indigenous and 13 non-indigenous). The 10 women answered screening questions regarding 48 (25.8%) children/adolescents and the 30 men provided qualitative information about 138 (74.2%) children/adolescents. Indigenous teachers only taught up to the fourth grade, and non-indigenous teachers taught between the fifth and eighth grades. This is because a college degree is mandatory for those teaching from the fifth to eighth grade, and only non-indigenous teachers had such prerequisites. The complete distribution of children/adolescents among participating teachers is presented in Table The parents or guardians and teachers of the participating children and adolescents signed informed consent forms. The study was explained in detail to children and adolescents before they assented to participating.The Achenbach System of Empirically Based Assessment (ASEBA) –18 was uAlthough not designed as diagnostic tools for ADHD, they have a high sensitivity to detect individuals at risk and probable comorbidities . Also, tThe questionnaires recorded the behavioural and emotional problems of children and adolescents. Scores were obtained for (a) 118 items of specific problems and two items of open/closed questions; (b) the eight-syndrome scales of the CBCL: anxious/depressed, withdrawn/depressed, somatic complaints, social problems, thought problems, attention problems, rule-breaking behaviour, and aggressive behavior; (c) two scales derived from the eight syndrome scales, termed internalizing problems  and externalizing (rule-breaking behavior and aggressive behaviour); and (d) total problems, consisting of the sum of the scores of the 118 problem items , 19.-IV (DSM-IV). These are named affective problems, anxiety problems, somatic problems, attention deficit/hyperactivity problems, oppositional defiant problems and conduct problems [Also, the questionnaires presented six probable diagnoses compatible with the Diagnostic and Statistical Manual of Mental Disordersproblems .Each question had three possible answers . The questions referred to the last 6 and 2 months of life, in the CBCL and TRF, respectively. The cut-off points of the sum of the scores provided three categories: clinical (> 63), borderline (≥ 60 and ≤ 63) and nonclinical (< 60) .The positive predictive value is high in the tracking of behavioral and emotional problems of children and adolescents of different cultures , 25. TheFor this study, we used the data equivalent to the DSM-IV diagnoses compatible with the CBCL and TRF scales-syndromes. Thus, the results were expressed as positive screening for affective problems (AffD), anxiety problems (AnxD), attention-deficit/hyperactivity problems (ADHD), oppositional defiant problems (ODD), and conduct problems (CD).The diagnostic criteria for ADHD from the DSM-IV included in both the CBCL and TRF were fails to finish the activities; cannot concentrate; cannot sit still; fidgets; impulsive; inattentive; talks much and loud. For the TRF: difficulty with directions; disturbs others; talks out of turn; disrupts class; fails to carry out tasks were also present .We proceeded with additional  adaptation of the CBCL and TRF from Portuguese to Karajá, because there were rarely exact matches between them. We tried to use instruments that were as attentive to the particularities of that culture as possible. This adaptation process was authorized by Dr. Thomas M. Achenbach, author of ASEBA.Additional culturally appropriate procedures occurred at various times. Initially, individuals from different social levels of the ethnic group were interviewed. They included leaders, indigenous officials in the service of National Health Foundation (FUNASA/MS) and the National Indian Foundation of the Ministry of Justice of Brazil (FUNAI/MJ), as well as individuals from the general community. At this stage, some Portuguese terms were replaced with Karajá, to increase understanding of the issues. Then we performed three pre-tests and new adjustments to reach the maximum knowledge of the problems of the indigenous community.The Strengths and Difficulties Questionnaire (SDQ) –29 impac4−17 and SDQ Pr4−17, respectively, for parents or caregivers, and teachers of young people aged 4–17 years. Impact supplements assess the suffering and dysfunction in the personal, academic and socio-familial spheres [The Portuguese version consists of SDQ Pa spheres , 33, 34.The literature has demonstrated a disagreement between information provided by the parents/caregivers and the children’s teachers , 35, 36.Information was collected between July 2007 and November 2008. Only one (non-native) interviewer, a nurse responsible for the special indigenous health district (DSEI), applied the questionnaires. In this way, there was no risk of variation by more than one interviewer. This professional was the person best accepted by the Karajá, as they were already used to her presence in the village. She was trained by the lead author of this study before conducting the interviews. The questionnaires were applied first to teachers and then to parents or caregivers. We chose the direct interview method because many of the parents or guardians were illiterate. Teachers were also interviewed to standardize the collection.The data collected were stored and analysed by the Statistical Package for Social Science version 18.0 (SPSS 18.0). In the descriptive evaluation, we studied the variables of age, sex, and schooling. The age variable was divided into two categories (7–10 and 11–14 years of age). The variable education was divided between grades 1–4 and grades 5–8 of elementary school.The prevalence of signs and symptoms of ADHD and comorbidities was estimated for the results compatible with such diagnoses by DSM-IV in CBCL and TRF. For the analysis of the gender, age, and schooling variables, we used two categories: nonclinical  and clinical (positive triage cases). We chose such categories to reduce false positives, which would be more likely if we compared normal with altered . We analysed the answers from parents or guardians (CBCL) and teachers (TRF) separately. Finally, we investigated the combined responses of the interviewees, considering as positive those cases for which both information sources agreed (CBCL and TRF).We initially analysed the results without considering the negative impact of the problems and then analysed them considering the negative impact. In the first situation, we observed the prevalence estimated by the positive cases for ADHD, according to the CBCL and TRF individually and in combination. In the second situation, we considered only the triage cases with the SDQ supplement indicating the negative impact. Regarding the negative impact, we considered as positive those cases with positive scores by both parents/caregivers and teachers.A combination of assessment strengths from the ASEBA and SDQ screening instruments was used, including both parents/legal guardians and teachers as information sources. Where the ASEBA has a more detailed list of symptoms , the SDQFinally, we presented a case report to illustrate clinical presentations of symptoms observed during an interview, in the context of the health service delivered to the population on their tribes.χ2) was used for making comparisons of categorical variables between the groups. When the samples were too small, we used Fisher’s exact test. The Kappa index (κ) was used to assess the level of agreement between respondents (parents or caregivers vs. teachers) regarding the symptoms of ADHD. We also evaluated the concordance (κ) between the corresponding trait  and impact . The level of significance was 5% (p < 0.05), with a 95% confidence interval (CI).The chi-square test  without and 1.1% (CI95% 0.0–2.7) with functional impact  and the early school years (p = 0.039) (Table p = 0.009) (Table Eight participants (8/186) had positive ADHD screening by both responders (CBCL and TRF), without considering the functional impact Fig. . Consides p = 0.09 (Table s p = 0.09 (Table p < 0.001) among the positive screening cases for ADHD and the general population.We found ADHD comorbidity with ODD, CD, and AnxD in 100% of the cases with dysfunction (2/186). In the general population studied, the estimated prevalence of the same disorders were 2.7% for ODD (95% CI 0.5–5.4), 3.2% for CD (95% CI 1.1–5.9) and 2.7% for AnxD (95% CI 0.5–5.4). There was a significant difference in comorbidity rates . The clinical diagnosis made by the child psychiatrist was ADHD, according to DSM-IV criteria . Other fHow, in a culture that allows children total freedom, are parents bothered by ADHD-like behaviour? We observed that their behaviours extrapolated from those usually accepted. They hindered the life of the young person, the family, and the community, causing suffering and dysfunction. The first similarity between this community and other cultures was the search for help for disruptive behaviour in children. These were the main reasons for medical care in indigenous health posts: concerning mental health problems .The indigenous population is one of the most unassisted in Brazil and in the world . To our Rohde et al.  performeAlthough not designed as a diagnostic tool, the ASEBA inventories show high agreement with DSM-IV criteria for ADHD , 18, 39.The question of cultural interpretation applies both to the differences between the various ethnic groups and to those between informants about the same child . We emphJavo et al.  observedOn the other hand, the Sami are illiterate in their language , while tThe Norwegian versions of the CBCL and TRF could have problems of Sami–Norwegian equivalence . We beliAs in our sample, Javo et al.  found a 4−17 and Pr4−17) to assess functional impairment. The concordance rate between positive symptoms and negative impact was good in our study. However, there was a low agreement in the combination of answers from parents or caregivers and teachers.Like Javo et al., we used the CBCL and TRF for symptom screening and the respective SDQ supplement  disorders of 30–50% . The ratOne hypothesis for the high rates of comorbidities would be the fact that the Karajá tolerate the milder symptoms of ADHD. Therefore, those who were identified with ADHD symptoms would correspond to more severe cases and, thus, with higher comorbidities rates.As limitations of our study, we can cite the fact that the sample was systematically allocated. The sample loss (15%) could also represent a selection bias since due to constant village changes and dropouts, this group might have a higher hyperactive component. Although all the caregivers  were indigenous, there were indigenous (majority) and non-indigenous teachers interviewed. Perhaps there is a bias in the precise indication of what would be culturally accepted, or not, by non-indigenous teachers. Another limitation was the fact that we did not use diagnostic interviews. Despite these limitations, the current study included a significant sample of the population studied and a highly qualified professional conducted direct interviews with parents and teachers.We conclude that ADHD symptoms are prevalent among Karajá children and adolescents and that they impact and impair their lives. The occurrence of symptoms suggestive of ADHD among the Karajá was similar to that of countless other cultures. Therefore, we believe that the nature component of the disorder becomes apparent, although modulated by the nurture.From these findings, the need for studies evaluating the treatment of these children and adolescents becomes urgent. These results also reinforce the hypothesis that ADHD is not a consequence of cultural factors alone and that the nature component of the disorder becomes apparent, although modulated by the nurture.


It is estimated that up to a third of patients on opioid agonist therapy (OAT) have attention deficit hyperactivity disorder (ADHD). Treatment by ADHD medication, including a centrally acting stimulant (CAS) or atomoxetine is one of the essential approaches. This study evaluates the use of dispensed ADHD medications in the Norwegian OAT population in the period from 2015 to 2017. Types and doses of ADHD medications, co-dispensations of other potentially addictive drugs like benzodiazepines, z-hypnotics, gabapentinoids, and non-OAT opioids, as well as direct-acting antivirals (DAA) against hepatitis C infection, are investigated.Information about all dispensed ADHD medication, OAT opioids, and the defined potentially addictive drugs were recorded from the Norwegian Prescription Database. Dispensation rates, the types, and the doses of dispensed ADHD medications were estimated by summarizing the number of dispensations, and the dispensed doses. Logistic regression analyses were employed to assess the associations between ADHD medication, and OAT opioid use, and dispensations of other potentially addictive drugs and DAAs against hepatitis C infection.p = 0.01). Sixty percent of patients receiving ADHD medications were also dispensed other addictive drugs concomitantly in 2017. Similar results were found in 2015 and 2016.A total of 9235 OAT patients were included. The proportion of patients who were dispensed ADHD medication increased from 3.5 to 4.6% throughout the study period. The three most dispensed CAS were short- and intermediate-acting methylphenidate (55%), lisdexamphetamine (24%), and dexamphetamine (17%) in 2017. Buprenorphine, rather than methadone, as OAT opioid  was associated with being dispensed ADHD medication. Among patients who received CAS and OAT opioids each calendar year, the dispensed doses of methylphenidate increased from 63 mg/day in 2015 to 76 mg/day in 2017 (Co-prescription of ADHD medications was low among patients on OAT in Norway, considering a high prevalence of ADHD in this patient group. On the other hand, concurrent dispensations of multiple addictive drugs were common in this population. Understanding the underlying reasons for such prescribing is essential, and research on how to optimize ADHD medication of patients with ADHD receiving OAT is needed. The strong association between opioid addiction and attention deficit hyperactivity disorder (ADHD) is well known . StudiesLittle is known about the prevalence of co-existing ADHD and the utilization and the dose of prescribed ADHD medication among patients with ADHD on OAT. Additional use of other potentially addictive drugs makes ADHD assessment and treatment with ADHD medications more challenging. Psychosocial factors and medical conditions among these patients may also complicate diagnosis and the co-therapy with ADHD medication. Therefore, studies show substantial inter-country differences in co-existing ADHD prevalence (5–30%) , 16, andDuring the past years, the guidelines for ADHD worldwide recommend prescribing ADHD medication to patients on OAT with comorbid ADHD and those with other drug use disorders if they are abstinent from any illegal drugs , 10, 17.define the dispensation rates of ADHD medication and the types of ADHD medication dispensed per calendar year.assess whether the dispensations of ADHD medication per calendar year were associated with dispensations of benzodiazepines, z-hypnotics, gabapentinoids, non-OAT opioids, as well as direct-acting antivirals (DAA) against hepatitis C infection, types of OAT opioids, the number of dispensed OAT opioids, gender, and age in the study period.define the mean daily doses of dispensed ADHD medications, and the dispensation rates of benzodiazepines, z-hypnotics, gabapentinoids, and non-OAT opioids in 2017 among patients who were dispensed ADHD medication in the calendar year throughout the study period.Thus, this observational study was aimed to define dispensation rates of attention deficit hyperactivity disorder (ADHD) medications and potentially addictive drugs among patients on opioid agonist therapy (OAT) in the period from 2015 to 2017 in Norway. The aims were to:www.norpd.no). The NorPD contains information on all drugs dispensed from pharmacies, except for drugs administrated at hospitals, nursing homes, and outpatient clinics [All data were register data and were drawn from the Norwegian Prescription Database (NorPD). From January 1, 2004, all pharmacies are obliged to submit data for all dispensed drugs electronically to NorPD underlying the Norwegian Institute of Public Health  or International Classification of Primary Care 2 (ICPC-2) to get public drug expenses reimbursed in Norway. The diagnostic codes of reimbursed drugs are recorded in the NorPD. Only two medical indications are approved for ADHD medication expense reimbursements in Norway: Hyperkinetic disorder/ADHD (ICD-10: F90 and ICPC-2: P81) or narcolepsy (ICD-10: G47 and ICPC-2: P81). For narcolepsy, only CAS are reimbursed. The information on diagnostic codes for non-reimbursable dispensations are not collected in the NorPD.One-year’s dispensation rates of ADHD medication during the study period were assessed by summing all patients who received at least one dispensation of an ADHD medication per the calendar year. Furthermore, patients were divided into two groups “all medical indications” and “ADHD” for the years in the study period. The group named “ADHD” only included patients who were dispensed ADHD medications with reimbursement codes for ADHD. The group named “all medical indications” included all patients who received dispensations of ADHD medications, either they were reimbursed or not. Less than five patients were dispensed CAS on the reimbursement code for narcolepsy in the study period.The association with being dispensed ADHD medication, or not adjusted for age, gender, type of dispensed OAT opioids, the number of dispensed OAT opioids, being dispensed benzodiazepines, z-hypnotics, gabapentinoids, or non-OAT opioids were calculated per calendar year in the study period. Age and the number of dispensed OAT opioids were categorized according to the predefined categories or groups per year. All dispensed ADHD medication, and potentially addictive drugs were identified and categorized into four drug groups: “benzodiazepines or z-hypnotics,” “gabapentinoids,” “non-OAT opioids,” and “ADHD medication” per year. For each group, categorical variables were created by whether patients were dispensed one or more of the drugs in the drug groups or not. Dispensations of DAA were also included due to the frequent use of illicit stimulant drugs in the OAT population and the fact that DAA against hepatitis C infection has made treatment more applicable for these patients. Patients were defined to be dispensed treatment with DAA if they had at least one dispensation of DAA from 2011 and until the end of 2015, 2016, or 2017, respectively.The mean daily dose of each ADHD medication and the dispensation rates of benzodiazepines or z-hypnotics, gabapentinoids, and non-OAT opioids in 2017, were calculated among patients with at least one dispensation of ADHD medication and OAT, respectively, for each calendar year in the study period. These patients were assumed to have achieved medical continuity in their ADHD treatment and follow up treatment according to national guidelines. The mean daily doses of ADHD medication were calculated by summarizing the total volume of defined daily doses (DDD) of each drug that was dispensed for each patient per year . Furtherp-values are presented when appropriate. Multivariable analyses for categorical variables were performed by binary logistic regression. Being dispensed ADHD medication, as well as OAT at least once, respectively, during a calendar year, were defined as a dependent variable in the logistic regression model. Independent variables were age, gender, ‘the number of dispensations of OAT opioids,’ ‘benzodiazepines or z-hypnotics,’ ‘gabapentinoids,’ ‘non-OAT opioids,’ and ‘DAA.’ All these variables were defined categorically. The level of statistical significance was defined as p < 0.05. The Chi-square test and paired sample t-test were used to estimate differences in dispensed mean daily doses of ADHD medication in 2015 compared to 2017 among patients with at least one dispensation of ADHD medication and OAT, respectively, during a calendar year throughout the study period. All patients were censored from the calendar year they died. SPSS version 24 was used for all analyses.Means, medians, percentiles, percentages, 95% confidence intervals (CI), odds ratios (OR), and The Regional Committee for Medical and Health Research Ethics, REC vest, Norway, has approved the use of registry data for this study . No informed consent from included patients was necessary. The STROBE checklist was applied in the preparation of the study , followed by lisdexamphetamine (24%), dexamphetamine (17%), long-acting methylphenidate (9%), and racemic amphetamine (2%) : 1.6, 95% confidence interval (CI): 1.3–2.1) (Table p = 0.01) , the medical indications for these dispensations are not available for the researchers through NorPD. Further, gabapentinoids, benzodiazepines, z-hypnotics, and non-OAT opioids have different medical indications, and the indications have not been evaluated in this study. Second, the number of dispensed OAT opioids may be incompletely registered by the pharmacies. The self-reporting survey of OAT in Norway in 2017 showed that the mean frequency of dispensations of OAT opioids was four times a week . This fiCo-prescribing of CAS and atomoxetine was low in the OAT population in Norway, relative to the expected prevalence of ADHD in this patient group. Considering that up to a third of the OAT population is estimated to have ADHD, only 3.5 to 4.6% of patients received both ADHD medication and OAT opioids in Norway in the period from 2015 to 2017. Furthermore, 85 of 142 OAT patients who were dispensed ADHD medication each year throughout the study period were dispensed at least one dispensation of other potentially addictive drugs concomitantly in 2017. Generally, the polydrug use, including CAS, OAT, and other potentially addictive drugs, may lead to adverse side effects; however, a treatment combining several potentially addictive drugs in OAT patients using CAS has only been scarcely studied. Randomized-controlled trials evaluating ADHD medication in different doses are needed to improve the treatment of ADHD in the OAT population.Additional file 1. ATC codes for included drugs, or drug groups. ADHD = Attention deficit hyperactivity disorder, ATC = Anatomical Therapeutic Chemical (ATC) classification system, and OAT = opioid agonist therapy. An overview of drugs and drug groups included in this study.Additional file 2. Converting table of DDD to milligrams according to WHO’s standards. ATC = The Anatomical Therapeutic Chemical (ATC) classification system, ADHD = Attention deficit hyperactivity disorder, DDD = defined daily doses, mg = milligram, WHO = World Health Organization.Additional file 3. STROBE Statement. Checklist of items that should be included in reports of cohort studies