The Prevalence and persistence of ADHD have not been described in young Australian adults and few studies have examined how conduct problems (CP) are associated with ADHD for this age group. We estimate lifetime and adult prevalence and persistence rates for three categories of ADHD for 3795 Australian adults, and indicate how career, health and childhood risk factors differ for people with ADHD symptoms and ADHD symptoms plus CP.(i) full DSM-IV criteria; (ii) excluding the age 7 onset criterion (no age criterion); (iii) participant experienced difficulties due to ADHD symptoms (problem symptoms).Trained interviewers collected participant experience of ADHD, CP, education, employment, childhood experience, relationship and health variables. Three diagnostic definitions of ADHD used were Prevalence rates in adulthood were 1.1%, 2.3% and 2.7% for each categorization respectively. Persistence of ADHD from childhood averaged across gender was 55.3% for full criteria, 50.3% with no age criterion and 40.2% for problem symptoms. ADHD symptoms were associated with parental conflict, poor health, being sexually assaulted during childhood, lower education, income loss and higher unemployment. The lifetime prevalence of conduct problems for adults with ADHD was 57.8% and 6.9% for adults without ADHD. The greatest disadvantage was experienced by participants with ADHD plus CP.The persistence of ADHD into adulthood was greatest for participants meeting full diagnostic criteria and inattention was associated with the greatest loss of income and disadvantage. The disadvantage associated with conduct problems differed in severity and was relevant for a high proportion of adults with ADHD. Women but not men with ADHD reported more childhood adversity, possibly indicating varied etiology and treatment needs. The impact and treatment needs of adults with ADHD and CP and the report of sexual assault during childhood by women and men with ADHD also deserve further study. Attention deficit hyperactivity disorder (ADHD) describes a range of behaviours characterized by forgetfulness, carelessness, inattention, disorganization, distractedness, fidgetiness and impulsivity possibly associated with inhibitory deficits Known risk factors for childhood symptoms include low birth weight The expression of ADHD symptoms in adulthood vary from the childhood criteria listed in the DSM-IV Higher levels of disadvantage are associated with ADHD when conduct problems are also present (i) What is the sample prevalence rate for lifetime and adult ADHD in the Australian population? (ii) What is the rate at which symptoms persist into adulthood? (iii) Are adults reporting ADHD symptoms more intensely exposed to childhood risk factors? (iv) How are Australian adults disadvantaged by ADHD symptoms? And (v) what is the impact of conduct problems on the disadvantage reported by adults with ADHD?We address several important questions. x2(1) = 0.03, p = .87].Participants were monozygotic (MZ) and dizygotic (DZ) twins and their siblings in total 1369 men and 2426 women, recruited through the National Health and Medical Research Council Twin Registry (ATR). The ATR was established to collect data from twins and their families for medical and scientific research. For this study, ATR members born between 1972 and 1979 were invited by mail to participate in a project examining the genetics of cannabis use and mental health. If a twin indicated a willingness to participate they were sent a pack providing detailed information about the study and a consent form. The twins who then wished to be involved returned their written consent to the ATR along with their agreement to possible contact with additional family members. Recruitment was multi-stage and of the 3925 initial recruitment letters sent to families at least one twin from 2405 families responded giving a family participation rate of 63.7%. The individual participation rate described in Ethics approval for this study was provided by the Queensland Institute of Medical, Research Human Research Ethics Committee, ATR ethics and Washington University School of Medicine Human Research Protection Office. Written and informed consent was provided by all study participants.Data were collected using a combination of computer assisted telephone interview (CATI) administered by trained research interviewers and either an online or paper version of a Health and Lifestyle Personality Questionnaire (HLPQ). The CATI was structured to collect self-reported sociodemographic variables; family environment during childhood, school grades, educational attainment, emotional and physical well-being, marital status, income level, employment, sexual assault prior to 18 and data relevant to psychiatric classification. The Semi-Structured Assessment for the Genetics of alcoholism  career path, childhood circumstances associated with poor outcomes (childhood risk factors) and health and lifestyle variables. The career related variables included educational attainment and within the Australian school system there were two valid exit points at which students could gain recognition of achievement; either year 10 or years 10 and 12, but students may have chosen to leave at any time up to year 12. Scholastic and trade qualifications could also be attained through a college of Techincal and Further Education (TAFE). Level of educational attainment was coded as 1≤ year 10, 2 = year 11 or 12, 3 = TAFE and 4≥ degree. School grades during primary and high schools were coded as 1< average, 2 = average and 3> average and weekly income was condensed into categories; 1≤ $481, 2 = $482−$769, 3 = $770−$1442, and 4≥ $1442. Occupation was also coded into four categories; 1 = not working, 2 = student, 3 = working and 4 = homemaker.The sociodemographic variables were divided into three categories; those related to 1< average, 2 = average and 3> average. Conflict with parents, parental arguing, parental tension and drinking were scaled as; 1 = never or rarely, 2 = sometimes and 3 = often, parental rules were coded as 1 = inconsistent and 2 = consistent. Being raised by both parents to the age of sixteen was coded as 1 = no and 2 = yes and experiencing a sexual assault during childhood was coded as 1 = no, 2 = once, 3 = more than once. Health and lifestyle variables included marital status which was coded as; 1 = unmarried, 2 = prior marriage and 3 = married, physical and emotional health were measured as 1 = poor, 2 = fair, 3 = good or excellent. The continuous variables of days ill per year  and birth weight  were coded as 1 = 0−10, 2 = 11−30, 3>30 and 1<2333 g and 2≥2333 g respectively. The report of problem drinking was coded as 1 = no and 2 = yes. The low birth weight represented in analyses (2333 g) was at the 10th percentile for twins p = .52) or hyperactive-impulsivity symptoms (p = .43).Childhood risk was primarily measured by circumstances within the family during childhood between the ages of 6 and 13. The families socio-economic status was coded as lifetime risk and current diagnoses. First, full DSM-IV diagnostic criteria for primary inattention, hyperactive-impulsivity and combined ADHD: (A) over a 6-month period the experience of six of nine possible inattentive or hyperactive-impulsive symptoms for each subtype respectively and at least 6 inattentive and 6 hyperactive-impulsive symptoms for the combined subtype; (B) symptom onset by the age of 7 years; (C) symptoms experienced across two life arenas - either home and school for childhood retrospective report and work for the report of continuing symptoms, home and socializing or school/work and socializing; (D) problems resulted from ADHD symptoms; and (E) exclusion of autism and Asperger’s disorder. The second ADHD measure included all criteria with the exception of B – the age of symptom onset was left open. The third measure represented participants who met only criteria C (impairment across two settings) and/or D . The report ADHD symptoms caused problems in a persons’ life was our measure of clinical relevance. Participant report of symptoms within the previous 12 months differentiated lifetime risk from current diagnoses.Participants’ report of ADHD symptoms were used to create three diagnostic definitions of ADHD and each was divided into i. aggression to people and animals, ii. destruction of property, iii. deceitfulness or theft and/or serious violation of rules; (B) symptoms have caused problems in social academic or occupational functioning; and (C) a diagnosis of anti-social personality disorder was not applicable. Antisocial personality disorder (ASPD) was diagnosed according to the listed criteria A and B, with the inclusion that; by the age of 15 three symptoms had been experienced within 12 months.Data on symptoms of conduct disorder were collected if participants reported they occurred prior to the age of 18. A symptom count of conduct problems was entered as a covariate in regression analyses and the following DSM-IV criteria were used for diagnosing ADHD with co-morbid conduct problems: (A) three symptoms across three behaviours including – Once a twin initiated contact with the ATR an interview time was arranged. The CATI response booklet was sent to the respondent along with information guiding them to the online HLPQ and they were invited to complete the HLPQ prior to the CATI. During the interview respondents, referred to the CATI response booklet when asked by interviewers to indicate their responses. All interviews were recorded and reviewed by editors to ensure consistency across the duration of the study and interviewers.alcohol problem and days ill per year. These two variables were only available for a reduced subset of participants due to a change in protocol . All analyses were run with available data.Across variables there were little missing data. The missingness in inattention and hyperactivity-impulsivity items was 2.1%, conduct problems had 3.1% to 4.1%. The career, childhood risk and health related variables had 1.0%, 0.5% and 0.2% missing values respectively, with the exception of Persistence of ADHD into adulthood was calculated with survival analysis using the age of participants at symptom onset, the age at which symptoms were last experienced and whether or not symptoms were remitting. This method takes into consideration the entry and exit of participants to and from the pool of individuals affected by ADHD across time. So participants with a late symptom onset were excluded from the final rate because they did not contribute to the estimate of prevalence before the first remission occurred. Three prevalence rates were calculated corresponding to the three sets of criteria used to measure symptoms of ADHD. Each of the prevalence estimates was standardized to the gender and education distributions of the Australian population to account for the higher prevalence of ADHD in men and the association between ADHD and lower educational attainment.conduct problem symptom count as a covariate. The results of these analyses were weighted to account for the similarity of response among related participants. Weighting was calculated using the averaged correlation between twins within MZ and DZ pairs for ADHD as a proportion of the total variance Ordinal logistic regression (OLR) was used to examine the relationships between ADHD symptoms, conduct problems and sociodemographic variables. x2(1) = 7.22, p = .007] but not persistence of symptoms  was higher for men. Prevalence rates were not associated with birth year which was represented in quartiles x2(3) = 0.64, p = .89, possibly due to the restricted age of the sample. The prevalence of antisocial personality disorder within this ADHD categorization was 35.5% (SD = 6.3%) compared to 3.4% (SD = 0.1%) in the full sample. MZ twins, DZ twins and singletons did not differ significantly in prevalence of symptoms and diagnoses .The lifetime prevalence of ADHD was 0.9% for women (21/2406) and 2. 1% for men (28/1341). There were 0.5% of women (12/2415) and 1.4% of men (19/1350) with current ADHD, standardized and raw prevalence estimates across education and gender categories are presented in x2(1) = 6.75, p = .009 and x2(1) = 1.83, p = .18 respectively and there was no difference in ADHD prevalence across birth year x2(1) = 1.03, p = .79. There were 26.7% (SD = 3.5%) of these participants meeting criteria for antisocial personality disorder.The lifetime prevalence of ADHD when only age of onset criterion was dropped was 3.8% for men (50/1319) and 2.4% for women (58/2369). Symptoms were reported as current by 1.2% women (29/2398) and 2.4% men (32/1337). Since not all participants had experienced symptoms by the age of the first remission (which was 14), we adjusted for both left and right censoring to estimate a persistence rate of 60.2% (46.9% –77.2%) for men and 40.3% (28.2% –57.4%) for women. Again the prevalence but not persistence of symptoms was significantly higher for men C impairment is evident in two or more settings and/or D impairment is clinically relevant. It was not a requirement that these participants met criterion A (six inattentive or hyperactive-impulsive symptoms) so the lifetime prevalence of problematic ADHD symptoms–3.1% for women (74/2352) and 4.8% for men (63/130) – was higher than the previous two categories. There were 2.9% and 1.4% of men and women respectively within this category, reporting current symptoms and this gender difference was significant x2(1) = 9.77, p = .002. Persistence of symptoms into adulthood was 55.7% (42.5% –73.1%) for men and 24.6% (10.3% –58.5%) for women, this difference reached significance x2(1) = 3.73, p = .05. Again there was some censoring due to a later age of symptom onset for participants with problem symptoms and all had experienced at least six or more ADHD symptoms, which was the criterion for asking whether or not symptoms were experienced as problematic. The prevalence of anti-social personality disorder within this group was 23.9% (SD = 2.8%).The problem symptoms category represented participants meeting DSM-IV ADHD criterion p<.01 and p<.05 respectively). Men and women reporting low grades in primary and high schools also reported more symptoms of inattention (p<.001) and hyperactivity-impulsivity (p<.05). The odds ratios indicated this relationship was strongest when conduct problems were also present. Both women and men reporting inattentive symptoms earned less money each week than participants with fewer or no inattentive symptoms. Participants with higher levels of inattention were more likely to be unemployed (p<.05) and the likelihood increased when they had also experienced conduct problems (p<.001).Ordinal Logistic Regression of career related variables onto ADHD symptoms was conducted for the full sample and results are provided in p<.05). A relationship between hyperactive-impulsivity and being raised in a one-parent household was predicted by comorbid conduct problems (p<.05) but this relationship was suggested for inattention with conduct problems and hyperactive-impulsivity only. There was a strong relationship between childhood sexual assault, inattentive and hyperactivity-impulsive symptoms (p<.001 and p<.01 respectively) whether or not conduct symptoms were also experienced. There were significant gender interactions; conflict with parents, parental arguing, parental tension and parental rules predicted more symptoms of ADHD for women but not men. This relationship was strongest for women reporting conflict with their parents during childhood (p<.001), but also apparent with the report of more parental tension (p<.05). Inconsistent parental rules predicted inattention with and without conduct problems for women but not for men . Parental arguing predicted inattention and hyperactivity-impulsivity for women but only when they occurred with conduct problems (p<.05). There was no systematic relationship between parental drinking and symptoms of ADHD. Results for gender specific analyses are available from the first author on request.As summarized in p<.05 to p<.001; p<.001). However there was no significant effect of birth weight when gender was differentiated, though females generally have a lower birth weight than males p<.05).Poor physical and emotional health were predicted by higher levels of inattention and hyperactivity with and without conduct problems . Past prevalence estimates of ADHD within adult populations range between 1.0% found in Holland The persistence of ADHD into adulthood occurred for 24.6% to 63.0% of ADHD affected women and men across ADHD categorizations. The highest degree of persistence occurred for adults meeting full DSM-IV criteria, symptom severity has previously been found to predict symptom persistence Our finding that childhood risk factors did predict higher levels of ADHD symptoms supports previous research indicating an association between childhood adversity and retrospective report of ADHD The disadvantage adults with ADHD symptoms reported included lower educational attainment, loss of income, increased unemployment, poor physical health, more days ill each year, reduced likelihood of marriage and fewer close friends. The disadvantage associated with comorbid conduct problems did not appear to differ qualitatively from that associated with ADHD symptoms but was more severe. The report of conduct problems was uniquely associated with being raised by one parent only, lower socio-economic status, more conflict with parents and problem drinking though these trends were evident for participants with ADHD symptoms only. The lifetime prevalence of conduct problems for participants with no history of ADHD was 6.9%. For participants with a history of ADHD this rate increased to 67.9% and the high incidence of antisocial personality disorder indicated ongoing and severe difficulties for ADHD affected adults.There were several limitations that influence the interpretation of our findings. The survival analysis was based on the report of the first and last experience of symptoms. Even though a participant may have met full diagnostic criteria the variation of these symptoms across time could not be measured precisely. Further the use of a CATI rather than a clinician appraisal to diagnose ADHD may have resulted in a loss of rapport only possible in a face-to-face interview, and influenced our findings. Our prevalence rate of adult ADHD was comparatively low to previous estimates and the adjustment made for gender and education could not fully account for this difference and we were unable to estimate the effect due to methodological variation in ADHD diagnoses. The degree to which missing values were random could not be defined. But, participants returning the HLPQ and not completing the CATI did not appear to differ from full participants in rates of substance use, autism, Asperger’s syndrome or ADHD (data are not shown).In conclusion our findings indicate ADHD in adults occurs for a high proportion of people who report symptoms during their earlier years. These symptoms are associated with income loss for men and women and according to our criteria affect approximately 250 000 to 750 000 Australians at a conservative estimate. Identification of disadvantage associated with subclinical ADHD symptoms and associated conduct problems in adults and a possible need for treatment will help to alleviate personal, familial and community issues resulting from the symptoms reported by these adults. Further research into the increased number of ADHD symptoms associated with childhood adversity for women and for women and men also experiencing a sexual assault during childhood could indicate ways in which symptoms and etiology varies across gender and how treatments may also need to vary.


There are numerous event-related potential (ERP) studies in relation to attention-deficit hyperactivity disorder (ADHD), and a substantial number of ERP correlates of the disorder have been identified. However, most of the studies are limited to group differences in children. Independent component analysis (ICA) separates a set of mixed event-related potentials into a corresponding set of statistically independent source signals, which are likely to represent different functional processes. Using a support vector machine (SVM), a classification method originating from machine learning, this study aimed at investigating the use of such independent ERP components in differentiating adult ADHD patients from non-clinical controls by selecting a most informative feature set. A second aim was to validate the predictive power of the SVM classifier by means of an independent ADHD sample recruited at a different laboratory.Two groups of age-matched adults  performed a visual two stimulus go/no-go task. ERP responses were decomposed into independent components, and a selected set of independent ERP component features was used for SVM classification.Using a 10-fold cross-validation approach, classification accuracy was 91%. Predictive power of the SVM classifier was verified on the basis of the independent ADHD sample (17 ADHD patients), resulting in a classification accuracy of 94%. The latency and amplitude measures which in combination differentiated best between ADHD patients and non-clinical subjects primarily originated from independent components associated with inhibitory and other executive operations.This study shows that ERPs can substantially contribute to the diagnosis of ADHD when combined with up-to-date methods. Attention-deficit hyperactivity disorder (ADHD) is a clinically heterogeneous disorder that is associated with high financial costs, stress to families and interpersonal relationships, and adverse academic and vocational outcomes . AccordiOne of the most influential theoretical models of ADHD postulates that a deficit in behavioral inhibition is the core of ADHD ,8. AccorIn contrast to spontaneous EEG activity, event-related potentials (ERPs) reflect phasic activity of cortical neurons. They are electrophysiological responses to an internal or external stimulus and are obtained by averaging the brain's electrical response to the stimuli over a number of trials. ERPs exhibit a number of characteristic peaks and troughs - their components - which are associated with underlying stages of sensory-related and action-related information flow in various cortical areas. A particular ERP component can be characterized by its eliciting condition, polarity, latency and scalp distribution (topography). There are a multitude of tasks that are used to elicit ERPs. These tasks cover a variety of distinct cognitive operations such as the detection and recognition of stimuli, updating working memory and the initiation, suppression and monitoring of action. In the context of ADHD, ERPs have been investigated in a large number of studies and a substantial number of ERP correlates of ADHD could be identified . Being pApplying this paradigm, several group differences relating to different ERP components have been found between ADHD and control subjects. Smith et al. , when exInvestigating the functional significance of ERP components is the focus of ongoing research. However, given that ERP components are highly specific to the behavioural paradigm used for their elicitation, associating ERP components with a clear functional meaning poses a serious challenge. For instance, Folstein and Van Petten  concludeThere are a limited number of studies investigating whether ERP measures of brain function are of diagnostic utility and can be used to reliably classify normal controls versus patients with ADHD . The clIn recent years, new non-linear methods such as support vector machines (SVM), a group of supervised learning methods that can be applied to classification, have emerged in the field of electroencephalography -27. UsinIn a recent study, Mueller et al.  were ablThe purpose of this study was threefold. The study was aimed at examining the utility of independent ERP components in classifying adult ADHD patients and non-clinical subjects, at separating a combination of features which prove most informative for the classification and at validating the predictive power of the SVM classifier by means of an independent ADHD sample. In more general terms, this study is part of a work aiming at identifying biological markers in terms of personalized medicine.Two age- and sex-matched groups participated in the study, each consisting of 37 female and 38 male subjects aged between 20 and 50. The mean age in the ADHD group was 36.05 years (SD 8.42). ADHD subjects were recruited by advertising the study in the media and by notifying psychiatrists and ADHD associations of the study. Inclusion in the ADHD group was based on the DSM-IV criteria for ADHD . 24 subjThe control group consisted of 75 age- and sex-matched healthy subjects recruited from the local community. The mean age in the control group was 36.08 years (SD 8.60). Subjects were recruited by advertising the study in local media, companies and associations. Subjects who had suffered a head injury with subsequent loss of consciousness and subjects suffering from neurological or systemic medical diseases were excluded from the study. Furthermore, control subjects had to score lower than the level of clinical significance on a symptom checklist . No conFor the purpose of verifying classification performance based on the main samples described above, a new sample was recruited. The ADHD validation sample consisted of 6 male and 11 female subjects, who were tested at the Neuropsychological Unit of the Helgeland Hospital in Mosjøen, Norway. The subjects were recruited from four psychiatric outpatient clinics in Helgeland hospital and from doctors in the same region. The age range was 18 to 47 years, the mean age was 30.5 years (SD 9.4). Inclusion in the group was based on the DSM-IV criteria for ADHD, and exclusion criteria corresponded to the criteria used for the main ADHD group with regard to both medication and existing diseases.The study was approved by the competent ethics committees in Switzerland (ethics committee Grisons) and Norway (REK nord). Written informed consent was obtained from all participants after the procedure had been explained to them.ADHD symptoms were assessed by means of Barkley's Current Symptoms Scale and Childhood Symptoms Scale for retrospective recall of childhood symptoms . These sIn order to measure current psychological distress and symptoms in both the patient and non-patient samples, the Brief Symptom Inventory  was applThe subjects' health history was assessed using the Health History questionnaire compiled by Barkley and Murphy . The forCriteria for inclusion in the ADHD group were assessed during a structured clinical interview for adults with ADHD . The intThe task is a modification of the visual two-stimulus go/no-go paradigm and has been used for examining the electrophysiological mechanisms of executive operations on various occasions ,23. ThreIn trials with a picture of an animal presented as the first stimulus the subject is supposed to prepare to respond. This preparatory set is referred to later as "continue set". In trials with a picture of a plant presented as the first stimulus the subject does not need to prepare to respond. This preparatory set is referred to as "discontinue set".The responses of the subjects were recorded on a separate channel on the amplifier. The averages across trials for response latency and for response variance were calculated individually for each subject. The number of omission errors  and of commission errors  were also individually computed for each subject.The procedure has been described in detail elsewhere . QuestioControl subjects were tested in a single session. After filling out a series of questionnaires, EEG data was acquired. Lastly, the subjects were given a working memory task, whose resulting data is not relevant to this paper.EEG was recorded using a Mitsar 201 (Mitsar Ltd.) and sampled at 250 Hz with a bandwith of 0.5 to 50 Hz. Impedance was kept below 5 KOhm for all electrodes. Electrodes were placed in accordance with the International 10-20 system using an electrode cap with tin electrodes . Linked ears reference montage was changed to average reference montage prior to data processing. Artefacting was accomplished according to the procedure described in our previous paper .The goal of Independent Component Analysis (ICA) is to utilize the differences in scalp distribution between different generators of ERP activity to separate the corresponding activation time courses . ICA decThe assumptions that underlie the application of ICA to individual ERPs are as follows: 1) summation of the electric currents induced by separate generators is linear at the scalp electrodes, 2) spatial distribution of the components' generators remains fixed across time, 3) each source signal can be modeled as an independent and identically distributed process ,33. In aAs in any iteration procedure, different datasets  do not necessarily provide the same ICs. To assure that the components separated in the present study are stable and, consequently, reflect common features of ERPs, we first constructed ICs for the control and the ADHD dataset separately. For further analysis, we only chose ICs which were present in both groups. ICs separated in the respective groups were assumed to correspond to each other if the correlation coefficients of both their topographies and activation curves were higher than 0.5.For decomposing the individual ERPs of the validation sample into independent components, the same spatial filters which had been constructed for the main sample were used.The sLORETA  imaging Classification of subjects into ADHD and control subjects is based on features derived from the individual IC activation curves, comprising latency as well as maximum/minimum and average amplitude values. The automated feature extraction procedure used in this study corresponds to the procedure used in our previous work .In order to reduce the number of possible features, for each of the ICs only the time courses at the site showing the most distinct grand average amplitudes were entered in the feature selection procedure. As to continue- and discontinue-set-specific ICs, only the activation curves of the dominating condition were entered in the feature selection procedure. Go/nogo (continue-set) components 4 and 8 (see results section) showed similar amplitude values in both conditions and therefore the activation curves of both conditions were selected for feature extraction. As to the preparatory-set-independent ICs, activation curves of the ignore condition were selected for feature extraction.Classification was performed by means of a support vector machine (SVM). Support vector machines are classifiers which originate in machine learning. The supervised learning algorithm seeks to provide the best possible separation of predefined groups in a multidimensional space on the basis of a number of training samples. A specific description of the support vector machine used in this study can be found elsewhere . More exThe presented support vector machine builds a classifier based on a given set of features. However, being based on different feature types and ICs, the number of extracted features for each subject is very large and would result in an overfitting of the SVM classifier. To select an appropriate set of features the predictive power of the resulting classification routine has to be considered. A popular technique to assess how the results of a statistical analysis will generalize to an independent data set is cross-validation . Data isValidation of the predictive power of the classifier was an important goal of this study. Accordingly, the classification accuracy was further validated by training the SVM on the basis of the main samples data and testing the classifier on the basis of the independent ADHD validation sample data.The Student's t-test was used in order to assess statistical significance of the group differences related to reaction time and reaction time variance in the behavioral task. Because the variables were not normally distributed, the Mann-Whitney U test was used for assessing statistical significance of the differences related to the number of omission and commission errors in the behavioral task and related to the questionnaire data.Z = -11.2, p <.001), more current hyperactivity/impulsivity symptoms , and more current total ADHD symptoms . Correspondingly, the ADHD validation group reported a presence of more current inattention symptoms , more current hyperactivity/impulsivity symptoms , and more current total ADHD symptoms  compared to the control group. The main ADHD group and the ADHD validation group did not significantly differ regarding the number of symptoms on the Current Symptoms Scale.Mean and p-values related to the clinical scales are presented in table Z = -2.331, p <.05), higher interpersonal sensitivity , higher anxiety , higher paranoid ideation , and higher psychoticism  scale values.As for the BSI symptom dimensions and general indices, compared to the control group, the ADHD group showed significantly higher scale and overall values with regard to any measure , prolonged periods of sadness/depression (25.3%), significant appetite changes (17.3%), excessive fears/phobias (13.3%), and excessive anxiety (12.0%) were reported most frequently. In the ADHD validation group, the distribution of the most frequent concerns was as follows: periods of sadness/depression (58.8%), significant changes to sleep pattern (47.1%), conduct disorder (41.2%), and excessive anxiety (17.6%).Z = -5.0, p<.001) and commission errors , as well as significantly higher standard errors of reaction time mean (t(148) = 5.2, p<.001), compared to the control group. The groups did not significantly differ in terms of reaction time.Table Z = -3.7 p<.001) and a significantly higher standard error of reaction time mean (t(89) = 5.4, p<.001) in comparison to the control group. The groups did not significantly differ in terms of reaction time and number of commission errors.The ADHD validation group had a significantly higher number of omission errors . 114 ms corresponds to the median of the deflection's time ranges which were defined as +/- 1.5 standard units from the mean latencies.The final number of features used for classification was determined by checking the classification performance which was obtained by combinations of up to 10 features. Cross-validation accuracy scores indicate that the predictive power increases up to the fifth feature. The addition of further features does not substantially improve the classifier's performance and increases the risk of overfitting. Therefore, the final feature set was composed of a combination of five features with best classification performance, selected by the automated feature selection algorithm, and it consisted of the following features: minimum peak latency in the 112 to 168 ms range of BA 6 novelty component, minimum peak latency in the 360 to 416 ms range of BA 6 go component, minimum peak amplitude in the 0 to 56 ms range of BA 6 go component, minimum peak latency in the 440 to 496 ms range of BA 6 nogo component, and minimum peak latency in the 192 to 332 ms range of BA 37 ignore component.Cross-validation classification accuracy, using the main samples, was 91% correct classifications . When testing the predictive power by means of the independent ADHD validation sample, classification accuracy was 94%.In this study, we investigated whether features of averaged ERPs, which were decomposed into independent components by means of ICA, can be used for an accurate classification of ADHD and control subjects. For that purpose, a modification of the visual two-stimulus go/no-go task was used in order to obtain ERP responses from an ADHD and a control sample in four task conditions. The individual ERPs of the ADHD and the control sample were separately decomposed into independent components. Independent component analysis was applied to go/nogo condition ERPs on the one hand, and to novelty/ignore condition ERPs on the other hand. In the respective samples, twelve highly correlating independent components were found, with three of them being task-condition-independent, five being go/nogo-condition-specific, and four being novelty-condition-specific. These independent components were then reconstructed on the basis of the total sample data and provided a set of latency and amplitude features, which were used in the classification procedure. Classification of the adult participants into ADHD and control subjects was performed using a support vector machine. Using a 10-fold cross-validation procedure, classification accuracy was 91%. This accuracy in the discrimination between ADHD and control subjects is remarkable considering the wide age range of the subjects participating in this study and bearing in mind that various authors reported an apparent decline in the diagnostic utility of electrophysiological measures with increasing subject age ,46,47.This result is consistent with the classification accuracy obtained in an earlier study . In thatTo our knowledge, there are no other studies with the aim to classify adult ADHD patients and control adults on the basis of ERP data. There are a few studies on children, whose classification accuracies are considerably lower ,47-49. IA second aim of the study was to test the validity of the classifier. To do so, the SVM was trained with the main sample and the predictive power of the classifier was tested using an independent ADHD sample, which resulted in a classification accuracy of 94%. This result shows that the classifier, based on the ERP feature set identified in this study, is not specific to the study sample and can be applied to any ADHD patients examined in different places. However, the absence of an independent healthy validation sample may constitute a limitation to the validation procedure. Along with a consequential lack of specificity estimation, anomalies in the control group could have an effect on classification accuracy.In spite of the limitations mentioned above, the findings of the present study indicate that event-related potentials can make a significant contribution to the diagnosis of ADHD. However, in terms of personalized medicine, associating independent ERP components with a functional meaning can increase their utility as biomarkers by allowing well-directed clinical interventions. Three types of independent ERP components were identified in the present study: task-condition-independent components, go- and nogo-condition-specific components, as well as novelty-condition-specific components.The task-condition-independent components were localized in occipital and occipito-temporal areas. In view of these sources and given that all task conditions involve the presentation of visual stimuli, the condition-independent components are assumed to reflect stages of the visual information flow.The go and nogo conditions (continue set) require the exertion of executive operations such as the monitoring and inhibition of actions, which have mainly been related to the frontal lobe . The conAs for the discontinue set (i.e. novel and ignore conditions), four independent components could be identified which were present in both the ADHD and the control group. They all were dominant in the novelty condition. In the novelty condition, a novel sound is presented along with the second visual stimulus. Novel auditory  stimuli, which are not of relevance to the performance of the task, elicit a characteristic ERP component named P3a or novelty P3. The P3a component has been linked to different processes such as the orienting response or the detection and evaluation of novelty ,56,57. TThe feature set which was used for classification and which discriminated best between ADHD and control subjects primarily consisted of features derived from independent components presumably associated with the inhibition of an action , on the one hand, and with the parietally distributed P3b wave (BA 6 go), on the other hand. However, these features which in combination allow for a discrimination of the ADHD and control groups do not necessarily produce significant group differences when considered as separate features. Nevertheless, abnormalities in action inhibition correspond to Barkley's  influentThis study shows that event-related potentials can substantially contribute to the diagnosis of ADHD in adults. Furthermore, ERP biomarkers can objectify and personalize the disorder. The use of independent ERP components facilitates a precise determination of abnormalities with regard to cortical localization and temporal occurrence, and consequently provides an indication of their functional meaning. The method can successfully be used in clinical practice and enables the implementation and further development of personalized medicine.GC, VAG, VAP, GMB report no potential conflicts of interest.AM and JDK are members of the board of HBImed company. HBImed provides accesses to a referential database.AM, GC, JDK, VAG contributed to the study conception and design. GC, VAG, AM headed the acquisition of data. GC, AM, JDK, GMB, VAG, VAP have been involved in drafting or revising the manuscript. GMB and VAP made substantial contributions to the analysis of data by implementing support vector machine (GMB) and ERP decomposition by means of ICA (VAP). All authors read and approved of the final manuscript.


Background. The number of students with Attention Deficit/Hyperactivity Disorder (ADHD) enrolled in colleges and universities has increased markedly over the past few decades, giving rise to questions about how best to document symptoms and impairment in the post-secondary setting. The aim of the present study was to investigate the utility and psychometric properties of a widely-used rating scale for adults with ADHD, the Adult ADHD Self-Report Scale (ASRS-V1.1), in a sample of post-secondary students with ADHD.Methods. A total of 135 college students  with ADHD were recruited from Student Disability Services in post-secondary institutions. We compared informant responses on the ASRS administered via different modalities. First, students’ self-report was ascertained using the ASRS Screener administered via telephone interview, in which they were asked to provide real-life examples of behavior for each of the six items. Next, students self-reported symptoms on the 18-item paper version of the ASRS Symptom Checklist administered about 1–2 weeks later, and a collateral report using an online version of the 18-item ASRS Symptom Checklist. Students also completed self-report measures of everyday cognitive failure (CFQ) and executive functioning (BDEFS).Results. Results revealed moderate to good congruency between the 18-item ASRS-Self and ASRS-Collateral reports (correlation = .47), and between student self-report on the 6-item telephone-based and paper versions of the ASRS, with the paper version administered two weeks later (correlation = .66). The full ASRS self-report was related to impairment, such as in executive functioning (correlation = .63) and everyday cognitive failure (correlation = .74). Executive functioning was the only significant predictor of ASRS total scores.Discussion. Current findings suggest that the ASRS provides an easy-to-use, reliable, and cost-effective approach for gathering information about current symptoms of ADHD in college and university students. Collateral reports were moderately related to self-reports, although we note the difficulty in obtaining informant reports for this population. Use of a telephone interview to elicit behavioral descriptions for each item may be useful in future research that is required to specifically test the utility of the ASRS in, for example, documenting and confirming current reports of impairment due to ADHD symptoms and its positive and negative predictive power for diagnosis. Attention-Deficit/Hyperactivity Disorder (ADHD) is a prevalent neurodevelopmental disorder that persists into adolescence and adulthood in about two-thirds of individuals e.g., , with anThe past couple of decades have witnessed an increasing number of young adults with ADHD who gain entrance into the post-secondary education sector and register with college or university Disability Service Offices (DSOs) to request accommodations. Twenty five percent of post-secondary students who are receiving services at DSOs have an ADHD identification . In the Self-report measures are frequently used to confirm ADHD symptomatology and levels of impairment in college-aged students. Although research on assessment with this specific population is limited, the broader literature on diagnosis of ADHD in adults yields strong evidence that adults are reliable reporters of current ADHD symptoms  and thatThe World Health Organization (WHO) Adult ADHD Self-Report Scale (ASRS) and its 6-item screener scale  are stanPresence of symptoms and severity ratings gathered using scales such as the ASRS, are necessary but not sufficient for providing documentation at DSOs. Impairment in functioning at college due to ADHD symptoms must be confirmed and specified . Scales Our overall aim in the present study, was to investigate the utility and reliability of using the ASRS questionnaire supplemented by interview questions with an informant report to screen for ADHD symptoms in a sample of post-secondary students. To do so, we investigated the congruence between self-report and a collateral report by a significant other , as well as the test-retest reliability of self-reported ADHD symptoms using different modalities across time, and congruency between the ASRS and self-report indices of executive functioning and cognitive failures in everyday life in college and university students presenting to DSOs.A total of 135 students with ADHD  were recruited from University Disability Services via email lists and flyers. Participants would understand the need for measuring current symptoms in order to register as eligible for this intervention study, which was the focus of the larger-scale study. Inclusion criteria were; (1) current enrolment in a post-secondary program, (2) a previous diagnosis of ADHD, (3) registration with respective university or college Student Disability Services, which requires documented evidence of a previously confirmed diagnosis of ADHD , and (4) aged 19–35. Exclusion criteria were; (1) uncorrected sensory impairment, (2) major neurological dysfunction and psychosis, and (3) current use of sedating or mood altering medication.p = .78), estimated IQ (p = .28), or current levels of psychological distress (p = .08), as determined by independent sample t-tests. Nor did the two groups differ in terms of sex distribution, Chi-square (1) = .23, p = .63, or in their reported scores on the psychopathy subscales . However, participants reported to be on medication were less likely to be registered with DSO as having comorbid LD, Chi-square (1) = 4.90, p = .03.Of this sample, 79 participants (59%) reported receiving medication for ADHD  and 56 participants (41%) did not . As can be seen from the summary data in Adult ADHD Self-Report Scale-V1.1 Screener (ASRS-V1.1): The 6-item ASRS-V1.1 (SRS-V1.1  was desiSRS-V1.1 . Using tSRS-V1.1  report hSRS-V1.1 .The data reported herein were derived from a telephone-based interview in which the interviewer (a trained psychology graduate student) administered the 6 questions of the ASRS-V1.1 Screener orally, with probes to elicit real-life examples of how the symptom typically manifests and its frequency . The ASRS-TIPS was always conducted before students or their significant-other completed the 18-item version of the ASRS-V1.1.Adult ADHD Self-Report Scale-V1.1 Symptoms Checklist (ASRS-V1.1): The 18-item ASRS v1.1 was designed to evaluate current manifestation of ADHD symptoms in people aged 18 years or older. This scale is based on the World Health Organization Composite International Diagnostic Interview ©2001, and the questions are consistent with DSM-IV criteria, but reworded to better reflect symptom manifestation in adults. This tool, which takes about 5 min to complete, has high internal consistency and concurrent validity . Also, all response boxes were white, meaning that there were no darkly shaded boxes. The tool was then uploaded onto a secure website (surveymonkey.com) for online completion by the significant other.Barkley Deficits in Executive Functioning Scale-Short Form (BDEFS): This Short Form, 2-item version of the BDEFS measures different constructs of everyday executive functioning in adults, including problem solving, organization, time management, self-regulation of emotions, self-restraint, and self-motivation. A summary score is produced from the sum of these subscales. A 4-point Likert-type scale is used to indicate frequency of occurrence . Using clinical and college samples of adolescents and adults with ADHD, this scale has strong reliability and validity : This self-report scale measures everyday failures of memory, motor functioning, and perception. Items are rated on a 4-point scale, quantifying the frequency of these mistakes . A total raw score is calculated from adding all 25 scores together. Studies have found that this scale predicts performance on laboratory measures of attention, and that it is a reliable scale : The SA-45 was used as a brief assessment of a general psychiatric symptomatology : The Vocabulary and Matrix Reasoning Subtests were used to estimate general intellectual ability ( ability .Kessler 10 Plus (K10+): The K10 is a self–report questionnaire which was used to obtain a global measure of nonspecific psychosocial distress. Questions probed the level of nervousness, agitation, psychological fatigue and depression in the past 30 days .The study was approved by the Research Ethics Boards of the participating universities and colleges (protocol reference #23977). All participants provided informed written consent before starting the study. Participants were told explicitly that withdrawal from the study, failure to complete any components of the study protocol, and task performance would remain confidential and would not affect their DSO services or academic accommodations.To confirm the robustness of students’ self-report of current symptoms of ADHD, we used several procedures. In all cases, informants were instructed to complete their ratings based on when the student was in an unmedicated state . First, we administered the six questions of the ASRS-TIPS orally by telephone (as part of the study intake procedure) and the student was asked to provide real-life examples for each of the six items, to ensure he/she understood the question and that the reported behavior was a reasonable example of an ADHD symptom. The interviewer prompted the student if needed for more details, clarification, or additional examples. The interviewer recorded the student’s self-ratings on an ASRS form, along with the behavioral examples of symptoms provided by the student, but did not use this information to override the self-ratings.www.surveymonkey.com, n.d.). The significant others were made aware that the purpose of the study was solely for research aimed to investigate cognitive functioning and the effectiveness of a working memory intervention program.Second, when each student came to the research lab for the first study assessment (T1), he or she was asked to complete both the 6-item Part-A  and the 12-item Part-B of the paper version of the ASRS (ASRS-v1.1), and to nominate and give us permission to contact a significant other who knew the student well enough to complete the ASRS . Third, the significant others completed a modified version of the 18-item ‘ASRS-V1.1 for Others’ using a secure, online software program (At the baseline assessment (T1), participants also completed other questionnaires, including the Kessler 10 Plus K10+: , an indeFor the first visit, participants were reimbursed for travel/parking costs ($25 CAD), with the knowledge that they would receive more substantial reimbursement ($150 CAD) for a second visit to be scheduled 2 to 3 weeks after the 5-week working memory training program, which was the focus of the larger study. Each visit required about 5 hrs to complete the full assessment, including the neural assessments, required for the larger-scale study.IBM SPSS Statistics version 21 was used to conduct the statistical analyses. For the analyses comparing group differences in scores, mixed model repeated measures ANOVAs were run with Medication status as a between-subjects factor and Congruency as a within-subjects factor . Relationships between variables were examined using Pearson correlations. Effects of sex were also investigated, separately, in all analyses, as a between subjects factor. Partial eta-squared values (n2) were computed to ascertain effect size (ES). According to n = 59) of the students’ nominated significant-other completed the on-line version of ASRS. For the medication group, the response rate for significant-others was 59% (n = 39) and it was 41% (n = 20) for the non-medicated group. Thus, the analysis across reporter type will be conducted on this smaller subset of participants who have a collateral report. This subgroup did not differ from the rest in age (p = .66), estimates of IQ (p = .43), current levels of psychological distress (p = .12), ADHD symptom severity (p = .22) or any reported scores on the psychopathology subscales , as determined by independent sample t-tests. A Chi-square test also showed no group difference in sex distributions (p > .28).Most of the students completed both the interview- and the paper-versions of the ASRS . By contrast, only 44% (t(132) = 3.38, p = .001. There were no main effects for sex  or medication status  on any other versions of the ASRS. Sex differences were found for the standard 18-item ASRS, as determined by independent samples t-tests, indicating that females reported a higher frequency of symptoms, F = 8.92, p = .004, ES = .14, showing that the students’ self-reported total score was significantly higher than that reported by their significant-other. However, as evident from the summary scores presented in p = .74). Similar analyses with Sex as a between-subject factor did not yield significant differences either (p > .30).The repeated measures ANOVA showed a significant effect of Informant, Most students received at least four responses marked in the ‘criterion boxes’ of the ASRS Other (98%) or Part-A of the ASRS Symptoms Checklist (98%). These findings suggest that for the majority of students, their current symptom profile, as reported by their significant-other or by themselves was consistent with an ADHD diagnosis in adults.r (59) = .46, p < .001 (see n = 4) fell in the shaded area, which indicates the ASRS-Other scores that fall below the 90th percentile. Specifically, 97% of the ASRS-Other scores and 100% of the ASRS-Self-Report scores were at or above the 90th percentile.The partial correlation, controlling for IQ, between significant-other and self-report ASRS was significant, .001 see . These d.001 see , the majF = .26, p = .61, ES = .002, suggesting that there is no difference between the paper- and interview-versions of the self-reported ASRS Screener, despite the differences in modality and time between administration of the two versions. Medication status was not significant as a factor (p = .34). Similar analyses with Sex as a between subject factor did not find significant differences either (p > .32).The repeated measures ANOVA showed no significant effect of Modality, r (131) = .66, p < .001 (see The correlation (controlling for IQ) between scores of self-reported symptoms across the ASRS-TIPS interview and Part-A of the ASRS paper version was significant, .001 see , suggestr (129) = .40, p < .001) and the CFQ total score (r (110) = .46, p < .001). The correlations between these scales were slightly stronger when using the ASRS 6-item paper version (CFQ: r (112) = .55, p < .001; BDEFS: r (131) = .52, p < .001). Of note, there was a stronger correlation between the full 18-item ASRS self-report total and both the BDEFS; r (131) = .62, p < .001, and CFQ; r (112) = .74, p < .001. This indicates that the full ADHD symptom scale covers more underlying constructs related to executive functioning and everyday cognitive failures as compared to the screener. The BDEFS measures specifically EF impairment, while the CFQ asks action orientated questions related to cognitive failure in everyday life; the two scales are strongly correlated: r (111) = .66, p < .001. These two scales are not measuring ADHD symptomatology for diagnostic cut-off; rather, they measure functional impairment experienced by those with ADHD. The moderate-to-strong linear relationships indicate some portion of overlap between the ADHD symptom rating scale and EF and cognitive failure rating scales. However, as would be expected, all three scales measure different aspects of ADHD symptomatology. A positive correlation between the BDEFS and ASRS is consistent with the finding that ADHD groups score in the high range on the BDEFS EF summary score . The BDEFS also best predicted the ASRS-Total score , over and above our measure of Psychopathology  or Psychological Distress  using a regression analysis.The total score from the 6-item ASRS screener (ASRS-TIPS) was moderately correlated with both the BDEFS EF summary score (r (59) = .36, p < .01).The ASRS informant score was not significantly correlated with the CFQ self-report total score. There was a moderate positive correlation between the ASRS informant total score and the BDEFS self-report  Students’ self-ratings of current ADHD symptoms were higher than scores reported by the significant other, but were moderately related to ratings by their significant-other; symptom ratings were all above clinical threshold for ADHD, regardless of informant or of the modality of administration; (2) Students’ initial telephone-based ratings of symptom frequency were strongly related to their self-reported ratings on a paper-version of the questionnaire completed one to two weeks later; the majority of students met threshold criterion on the initial interview-based ASRS as well as on their second self-rating (on Part-A) one to two weeks later; and (3) Students’ ratings of their ADHD symptoms on the 18-item ASRS were highly correlated with self-ratings of EF impairment and everyday cognitive failures. These correlations were not replicated between ASRS-other and self-report on the CFQ, however a moderate relationship was found between the ASRS-other and self-rated EF impairment. Scores of executive functioning were the only significant predictor of ASRS self-report.On the ASRS, respondents report the frequency of occurrence of each of the symptoms . Symptom frequency is often associated with symptom severity, thus scores on the ASRS-V1.1 Symptom Checklist may also indicate the severity of ADHD. Our findings are consistent with previous research in college students that found similar patterns between self and informant ratings, that is, current self-ratings were higher than informant ratings . Howeverr = .47), in this sample of college and university students. It is possible that the modest correlation was attributable in part to the smaller sample size: this analysis was based on only a subset of 59 participants with both self- and other-report. The low response rate by significant other might also be attributable to the fact that ratings were requested as part of a study rather than to validate symptoms for registration with DSO, so the motivation of the collateral informant may be lower. Future research is warranted on the feasibility of obtaining a collateral report for students in post-secondary education.The correlation between students’ self-report and their significant-other-report revealed only modest congruence . Systematic and detailed analyses of the students’ examples are in progress and will be reported elsewhere, but informal inspection of the behavioral examples indicated that the majority were excellent and valid examples of the specific symptoms. These data not only suggest that the students understood the question, but also afforded greater confidence in the robustness of their self-rating of the presence and frequency of occurrence of their current symptoms. Comparison of the students’ self-ratings on frequency of occurrence on six ADHD symptoms during interview and on the paper-version of the ASRS revealed excellent stability and reliability of reporting across a one to two week interval, despite the differences in modality used to obtain the information . This finding adds to the small body of literature indicating that adults can accurately self-report symptoms of ADHD. Administration of the ASRS 6-item Screener by telephone with probes for symptoms may increase confidence that symptom ratings are reflecting real life examples for the students. Moreover, the test re-test reliability of the ASRS was strong this college sample, suggesting that this tool may be useful for monitoring symptoms and severity across the semester.It is essential to keep in mind the limitations of this study, while considering the findings. First, this sample of college and university students with ADHD may be biased: they were already registered with DSOs and were highly motivated to seek and undergo intervention, despite the heavy time commitment and effort required to complete the working memory training. Thus, the findings may not be generalizable to the population of students with ADHD in the post-secondary education sector. Results are also specific to this group of post-secondary students with higher cognitive and academic ability as compared to peers who do not go on to university or college. Second, we were unable to confirm whether the participants actually met the DSM-IV criteria for ADHD, but the fact that they were all registered with the college and university DSOs suggests that their documentation of an ADHD diagnosis and impairments was adequate. We were unable to confirm co-occurring disorders in this sample; we did not have access to information about confirmed diagnosis for other disorders, such as learning disabilities or psychiatric disorders. Third, we were unable to confirm who the significant-others were in many cases  or that the students and their significant-others completed the 18-item ASRS-V1.1 questionnaire independently. However, that the students and their significant-others completed the questionnaire in different modalities (paper-version versus on-line electronic version) and at different time points (in the research lab versus on-line one to two weeks later), would have made it difficult for them to confer. Fourth, our comparisons of reported (self- versus significant-other) and modality (6-item screener items using interview or paper version) may be confounded by other factors, such as time or practice. It is also a limitation that we did not have informant reports for the BDEFS and CFQ. Finally, it is possible that financial incentive may have increased the student’s motivation to exaggerate symptom severity to be included in the study. However, the incentive was not great ($25) given the length of baseline assessment plus preceding intake telephone call .The ASRS is available in the public domain and provides a brief and cost-efficient tool that is readily administered by telephone, computer, or in paper format, to both the student and collateral informant. It is available in several languages and is recommended for clinical use internationally. In this sample, test-retest reliability across modality and time was strong, with moderate congruence between self- and other-report, indicating that more research is merited to further examine the use of the ASRS in gathering collateral information. The addition of probes for examples of each of the six ASRS Screener items in a telephone-interview version may afford the clinician greater confidence in the robustness of the student’s self-report of current ADHD symptoms. Use in conjunction with self-report measures EF may provide valuable information about everyday impairment related to ADHD symptoms for college students.The 6-item ASRS Screener and 18-item ASRS Symptom Checklist are feasible, reliable and cost efficient approaches to use in the assessment and monitoring of ADHD symptoms in the college population. The use of probes to elicit examples of each symptom as manifest in daily life along with self-ratings, in combination with the inclusion of a collateral report and self-report of executive functioning and cognitive failure, may afford increased confidence of accurate symptom reporting and provide corroborating evidence for symptom severity and functional impairment.10.7717/peerj.324/supp-1Supplemental Information 1Click here for additional data file.


The authors conclude that exposure to these environmental contaminants, and possibly others, may increase the prevalence of ADHD.Attention deficit/hyperactivity disorder (ADHD), the most frequently diagnosed neurobehavioral disorder in children, affects more than 5% of the population worldwide. Although the etiology of ADHD is poorly understood, characteristics similar to those seen in children with ADHD also have been observed in children and animals exposed to lead or polychlorinated biphenyls (PCBs). Two literature reviews in this issue provide an overview of ADHD diagnostic criteria and explore the parallels between behavioral test results from children with ADHD and findings from children and laboratory animals with developmental exposure to lead or PCBs Deficits in executive function and attention are key characteristics of both ADHD and developmental exposure to lead and PCBs. Executive function encompasses cognitive abilities critical to goal-oriented problem solving, such as working memory, response inhibition, cognitive flexibility , and planning. Attention revolves around alertness  and vigilance .ADHD has a strong genetic component but, like other neurodevelopmental disorders, appears to involve interactions between genetic, environmental, and social factors. Neuroimaging studies in children with ADHD have revealed alterations in brain regions that control executive function and attention, such as the prefrontal cortex. Alterations in catecholamine neurotransmitter signaling also are present in children with ADHD. Such signaling is potentially susceptible to damage by environmental toxicants.Developmental exposure to lead has been widely studied and is known to have a negative impact on cognitive function as well as on children’s behavior. Across studies, cognitive flexibility, vigilance, and alertness appear to be the functions most consistently affected by lead, but evidence also exists for negative effects on working memory, response inhibition, and planning. Several studies have reported associations between blood lead levels in children and ADHD.In contrast, researchers are only just beginning to explore the relationship between PCB exposure and ADHD diagnosis. Developmental exposure to PCBs is known to affect cognitive functions including working memory, response inhibition, cognitive flexibility, and alertness, although there appears to be little if any impact on vigilance. Animal studies further show that both lead and PCBs can reduce dopamine (a catecholamine) signaling in the prefrontal cortex of the brain.Although levels of lead and PCBs have declined overall in the environment and in our bodies, they remain public health issues. A better understanding of their roles in ADHD and other neurodevelopmental disorders is needed, and this knowledge could be useful in investigating other environmental agents including brominated flame retardants, bisphenol A, phthalates, organophosphate pesticides, and polyfluoroalkylated chemicals, all of which have been suggested by recent research to possibly be associated with ADHD.


Attention Deficit with Hyperactivity Disorder (ADHD) is one of the most prevalent disorders within the child population today. Inattention problems can lead to greater difficulties in completing assignments, as well as problems with time management and prioritisation of tasks. This article presents an intelligent tele-therapy tool based on Serious Games for Health, aimed at the improvement of time management skills and the prioritisation of tasks. This tele-system is based on the use of decision trees within Django, a high-level Python Web framework. The technologies and techniques used were selected so as to boost user involvement and to enable the system to be easily customised. This article shows the preliminary results of the pilot-phase in an experiment performed to evaluate the use of adaptive tele-therapies within a group of typically developing children and adolescents aged between 12 and 19 years old without ADHD. To do so, we relied on the collection of parameters and the conduct of surveys for assessing time management skills, as well as measuring system usability and availability. The results of a time management survey highlighted that the users involved in the trial did not use any specific or effective time management techniques, scoring 1.98 and 2.30 out of 5 points in this area for ages under 15 and over 16 years old, respectively. The final calculations based on the usability questionnaire resulted in an average score of 78.75 out of 100. The creation of a customisable tool capable of working with different skills, in conjunction with the replication of the current study, may help to understand these users’ needs, as well as boosting time management skills among teenagers with and without ADHD. Attention deficit with hyperactivity disorder (ADHD) is one of the most prevalent disorders within the child population today, affecting an estimated 5.29% of children worldwide . At presADHD usually manifests before the child is 7 years of age and is characterised by a certain degree of impulsiveness, inattention and excess of activity which does not match the child’s developmental age and is not appropriate in all situations that may arise . In addiet al., in their review of the literature, reported the most relevant features associated with these management problems. These include delays in the performance of specific tasks, problems related to turn-taking and premature answers [Time management is meant as the ability to use the resource of time in the most efficient way. This efficiency depends upon task management and prioritisation, routine planning and the ability to remember what is still to be done. These management, organisation and perception-related problems are detailed in the current definitions of ADHD ,7,8. Top answers , as wellTime management and the estimation of the likely duration of tasks differ among the users diagnosed with ADHD and those belonging to the control group, both in adulthood and in childhood. This difference has been reflected in many studies, especially by assessing the estimation of the length of short periods of time while performing specific psychological tests ,13,14,15Parents, doctors and teachers all report these types of behaviour, especially when they are linked to a lack of organisation and the acquisition of the appropriate time-planning strategies . OrganisIt is important to work on these management skills from childhood, providing the tools and the knowledge necessary to empower users. The improvement and promotion of these skills is directly connected, in most cases, to an improvement in school performance .Succeeding in motivating a child affected by ADHD to undertake academic activities is a key element in their development. There is a need to encourage their learning process and memory, concentration and time management skills using structured activities, clear rules and striking materials. The possible solutions or improvements include developing the interest of the group towards these activities, which, together with an early and continuous intervention , can achThe use of techniques employed in the design of videogames, combined with the establishment of certain goals, guidelines and rules which not only encourage the use of these type of technologies, but also serve to reinforce the training of such skills as working memory, stimulation of attention, concentration and the aforementioned management skills, represent a new type of effective therapy in their application to ADHD ,20.The online performance of these therapies provides the users involved with greater autonomy, fostering communication between participating groups  . MoreoveThe aim of this article is to assess the time management abilities of a group of typically developing children and adolescents, and to make a preliminary evaluation of the utility, usability and availability of the tool with respect to that group. These tests are intended to serve as guidance for adapting the tool presented in this article to final users, helping them to evaluate whether it could be used on a daily basis with users with and without ADHD. An important additional aim of the present study is to discuss whether the use of online game-based interventions fosters motivation and engagement in therapies. A supplementary objective is the evaluation of the use of online therapies to promote availability and convenience while using the tool. A final and future objective is to further assess the impact on the mid-term usage of this tool in teenagers with ADHD.To accomplish the stated aims, this article presents an online interactive tool aimed to assist in the prioritisation of tasks by children and adolescents with ADHD, based on the techniques used in Serious Games for Health. This tool has been designed to strengthen time management skills related to day planning, and to help parents and instructors to determine which areas cause more confusion when establishing organisation strategies. The ultimate goal of this application is to serve as guidance to final users, providing them with advice and recommendations about management, as well as giving them sufficient autonomy to plan their day, by prioritising certain tasks above others.In This section reviews the previous work available in the literature on the use of Serious Games for Health in the field of ADHD, as well as recent studies on the evaluation of time management skills in people with ADHD.This section analyses the use of Serious Games for Health in the diagnosis and treatment of ADHD. These games are specially designed to evaluate, diagnose, and be employed in therapies with children affected by ADHD, and have captured the attention of schools in recent years. The reason for this interest lies in the fact that many children who do not inhibit their hyperactive and/or impulsive behaviour, are capable of regulating it while playing videogames that motivate and foster their concentration ,24.It also should not escape notice, especially in relation to commercial videogames, that there seems to be evidence concerning the vulnerability of certain subgroups diagnosed with ADHD to videogame addiction ,26. NoneThe Supermarket Game has been developed in Brazil. It has been tested with 80 children diagnosed with ADHD and it has proven to be an efficient way of distinguishing among children who have, and who have not been diagnosed with ADHD. Decision-making algorithms are currently being optimised in order to discriminate among different types of ADHD [et al. designed a 3D virtual classroom to help in the diagnosis of ADHD based on the interaction with the system. This system was tested with eight children with ADHD and 10 non-diagnosed children with positive and accurate results [This section details the most relevant publications related to the diagnosis and evaluation of ADHD using Serious Games for Health. A game designed and tested to help in the diagnosis of ADHD called  of ADHD ,29. Seve results . The con results .Cyber Cruiser is a car rally-style game oriented towards the assessment of the executive function and prospective memory in children with ADHD, and has been used to establish differences in these skills among diagnosed and control groups in a sample of 80 children [Cognitive Carnival and Caribbean Quest in 2012 [children , with pochildren . The imp in 2012 ,35.At present, there exist some evidence indicating that videogames can contribute to the improvement, regulation and standardisation of some symptoms related to ADHD. The first therapeutic videogame available to do so was developed by Pope and Bogart in 1996, and is a modification of software developed by NASA for the training of pilots, based on the progressive adaptation of a computer programme to user attention levels . In 2001The Journey to Wild Divine, a 3D virtual world created to be controlled through biofeedback, and available for purchase. This game is controlled by relying on relaxation techniques, which are very useful in the regulation or monitoring of hyperactivity and impulsivity in children and adolescents with ADHD [Self City was released. It is oriented towards the improvement of social skills in adolescents diagnosed with ADHD and/or Pervasive Developmental Disorder. This game was developed in the shape of a 3D virtual world in which the adolescent is forced to cope with several situations [Another alternative is ith ADHD . At the ith ADHD  to measutuations .Play Mancer and Personal Investigator (PI). Play Mancer emerged from a European Cooperation Project in 2007, aimed at the creation of a common framework for the development of therapy-oriented Serious Games [PI is a 3D game specially designed to help adolescents with disorders through the use of Focused Solution Therapies—SFT and therapy games. It was initially tested with 4 adolescents with positive results [The games not specifically designed for ADHD, but oriented towards a wide spectrum of disorders in children include us Games ,42. PI i results .Robomemo  [In addition to the games specifically designed for the treatment and/or diagnosis of ADHD, among another disorders, commercial videogames adapted to ADHD therapy programs have also been used over the past few years, including  Sweden) . Table 1Building on the background developed in this section along with the information available in The Supermarket Game and CyberCruiser can be featured. These two projects have been tested with over 50 users.Due to the number of users involved in the testing of the project, which strengthens the systems described, Aula Nesplora, The Journey to Wild Divine and Play Attention need to be considered. These three systems are currently being used outside of the laboratory by professionals in psychotherapeutic or scholastic settings (Aula Nesplora and Play Attention). The Journey to Wild Divine is a commercial title available for online purchase.The next group of projects have been selected due to their use outside of a laboratory setting. In this section By examining This solution is focused on techniques used in the field of Serious Games, combined with work on time management skills, particularly centred on prioritising tasks. Furthermore, the fact that these exercises can be carried out online makes this tool accessible anywhere, and could serve as a consultation tool in everyday life.This section reviews the latest available interventions that are focused on the enhancement of time management skills and organisational behaviour in children and teenagers with ADHD. People diagnosed with ADHD may express organisational and time estimation problems ,56. Uponet al. performed an assessment, analysis and treatment of time management skills and planning deficits in children with ADHD [et al. evaluated the effect of medication  on Organisation, Time Management and Planning (OTMP) interventions. Results showed that some children remained resistant to treatment. In 2013 they concluded that the importance of performing OTMP interventions with children with ADHD was due to the promising clinical results [Abikoff and his colleagues have been working for the last decade on the analysis and impact of various approaches to organisational capacities and time management skills on children with ADHD. This paragraph outlines some examples of their research. In 2003, Abikoff, Gallagher ith ADHD . Later,  results .et al. demonstrated the importance of teaching organisational and academic planning and management guidelines to children with ADHD. They administered a Homework, Organization and Planning Skills (HOPS) intervention in a school setting [et al. developed a new school-home collaborative intervention (Collaborative Life Skills Program‒CLS) for youngsters with attention and/or behavioural problems. This study concluded that there was a reduction of symptomatology related to ADHD and there was an enhancement of organisational abilities [In 2013, Langberg, Becker  setting . In the bilities . Parker,bilities ,50.et al. assessed time estimation abilities in people with ADHD by performing the meta-analysis of fMRI images. They found potential normalisation effects in pre-frontal region linked with the use of long-term psycho-stimulant treatments [et al. evaluated the use of a 3D virtual classroom and concluded that children are vulnerable to a time-on-task effect on their performance. They stated that virtual reality is a reliable method to test ADHD children’s ability to sustain performance over time [et al. studied the use of HOPS intervention with a 3-month follow-up parent-rated organised action, on planning and homework completion behaviour. They stated that participants made significant improvements relative to the wait-list comparison, taking into account parent-rated assessment, while participants did not make significant improvements relative to the comparison group according to teacher ratings [In 2012, a considerable number of studies were published on the implications of time management and estimation deficits in people with ADHD. Hart, Radua eatments . In thisver time . Prior t ratings .et al., underlined the need to perform controlled studies on the use of specific interventions aimed at fostering executive functions [et al., engaged in the controlled monitoring of a small group of secondary students with ADHD, which showed an improvement in the use of organisational techniques in a school setting [In previous years other references can be found in the literature to the use of specific interventions for people with ADHD focused on time management skills. In 2008, Langberg, Epstein unctions . In 2006 setting .The authors have identified a need to develop tools that are fully available online at any time of the day. These tools should be ready to help and assess users outside of the specific interventions. That is why it is interesting to develop tools intended to complement the interventions focused on time management. These developments should be aimed at answering specific inquiries or doubts that may eventually arise. The system developed fits this description, as it provides final users with a consultation tool that fosters the autonomous self-management of time.This section shows the materials and methods used in the development and testing of the online application discussed in this article. The tool consists of a virtual interactive balance which, by making use of decision trees and user-entered parameters, is capable of prioritising between two proposed activities.Preliminary evaluation of the tool was made with a group of typically developing children and adolescents aged between 12 and 19 years old, with an average age of 16.23 years old.Seventeen randomly selected participants (seven women and 10 men), selected from a group of volunteers, took part in these trials. These users are resident in the Basque Country, Spain, have not been diagnosed with ADHD and have Spanish as their mother tongue. For individuals under 18 years old the approval of parents or guardians was requested prior to conducting the surveys.Users responded to questionnaires and tests independently, and used their own online devices  to do so. Participants were allowed to choose the time of day when they wanted to perform the evaluation of the tool. This evaluation took place during the months of July and August 2013.This section details the technical features of the system and describes the questionnaires delivered to the users before and after using the application. The online tool was produced in Django , the higTime Management Behavior Questionnaire (hereinafter TMBQ) by Macan et al. [For the evaluation of users’ time management skills prior to the test, the n et al. ,64,65 wan et al. ,67. The n et al.  during tSystem Usability Scale [SUS). This questionnaire consists on 10 items. These items were evaluated by using a Likert scale ranging from 1 (“strongly agree”) to 5 (“strongly disagree”). The completion of the questionnaire aims to continue to adapt the system to the users’ final needs. This questionnaire was available online, by means of the Google Forms tools during the months of July and August 2013.The discussed tool was evaluated by a user satisfaction test based on the ty Scale  . Items were evaluated by using a Likert scale ranging from 1 (“never”) to 5 . The purpose of this analysis was to establish the global situation of the user in terms of time management skills. This test took around 15 to 20 minutes to complete.The second stage was comprised of two sections: firstly, the use of the application, and secondly, the performance of a systematic evaluation of the questionnaire. The application test was conducted in the course of a full day, integrating it in a natural way into the users’ routine. This testing required various easy questions in the application, on the basis of the activities carried out. It took between 15 to 30 min, depending on the number of attempts users made.SUS [Once this battery test was finished, the users took the online usability questionnaire SUS , translaIBM—SPSS Statistics [.All the questionnaires and tests of the application were carried out in an autonomous way by users, outside of the laboratory environment. The two testing stages were carried out on their own devices, adapting the tests to the aim of the application; they took between 35 min to 1 h to be completed successfully. The results obtained in these two stages were uploaded and analysed in the atistics  predictiThis section shows the technical results of the system, and the ones obtained after the user- experience evaluation process.In this section the application design and development is explained. The application is an online platform developed in Django, which aids in the improvement of time management skills, and more particularly, in task prioritising.A tool was designed which consists of three parts: training, consultation and monitoring. All of them are subject to the same format, but their purposes differ; each one of them will now be explained in detail.a Tool for queriesThe consultation tool is a virtual balance in which users drag two activities that cause confusion by means of drag & drop techniques. In addition to dragging the activities, as it is shown in As it is shown in the decision tree in The decision tree was made following the ID3 algorithm , which dThe tool is fully configurable, and allows the user to add new activities to the system by entering a series of parameters. This way it is possible to scale the size of the system and cover new application activities and areas. The final purpose is to serve as a consultation system when working on task prioritising skills.On the basis of these parameters and of the area in which the tasks are classified, the system is responsible for evaluating them, and determining which one needs to be a priority by making use of the decision tree shown in b Tool for trainingIn the training tool the user is presented with two activities already placed in the balance, with a series of features associated with each one of them . The user must discern, using the data provided, which activity needs to be a priority.This game mode was developed in the way of a “quiz”, where users continue working on the task prioritising on the basis of the area  and the given parameters. c Tool for supervisorsThe supervisor tool keeps a history of all the queries made and the results obtained by each user from the training tool, showing the questions with their answers, together with the date of completion, in order to determine which areas are most difficult for each user. Furthermore, this tool allows users’ exercises to be customised, enabling questions to be added to the tool concerning the specific working skills of each user. This way the system is not only adapted to the exercises contained in the tool, but it is also fully customisable from the supervision area.This section describes the preliminary results of the tool shown in this article. These results were taken during the months of July and August 2013. The tests consisted of three parts: completing a questionnaire in Spanish about time management skills, performing some exercises by using the online tool, and finally, answering an online questionnaire about the usability of this tool.Participants were 17 users randomly selected from a group of volunteers. These users performed the referred tests on their online devices in the summer of 2013. Seven women and 10 men participated in these tests, as shown in p < 0.05) for the 12–15 year-old and the 16–19 year-old groups. The following sections describe each of the tests, along with the results obtained.In order to thoroughly analyse the results, the sample was divided into two age-groups. Due to the number of users that took part in this study, a Mann-Whitney non-parametric test was applied. This test was significant (a Test 1: TMBQTMB Questionnaire [The evaluation of participants’ time management skills was done by using a Spanish validated version of the ionnaire . This quAs shown in b Online tool evaluationThe section of the tool used for evaluating user experience is available online . This isc Test 2: SUS QuestionnaireIn order to evaluate system usability, the SUS questionnaire  was usedAs far as the answers are concerned, 16 participants, seven women and 9 men, out of the 17 initial participants in the trial, answered the system usability questionnaire. Due to schedule issues, one of the participants left the testing after the completion of the first questionnaire. This user belonged to the group under 15-years old. The inclusion of this user in the first test was not considered decisive in order to obtain the results. Please refer to This article addresses the issue of time management and the prioritisation of tasks in teenagers with and without ADHD diagnosis. In this section, authors attempted to answer the following questions, drawn from the section of this article which set out the objectives: Is it possible that the use of interactive and personalised content, such as serious games, encourage the use of tools to improve time management skills? Does the development of online tools foster their availability? Do users feel comfortable using these tools?Mobile devices are increasingly used in daily life, relegating computers to the background when it comes to short, specific activities . ResultsAccording to the literature mentioned in As explained in Based on the review conducted by the authors in et al. proposed a virtual development that implied the first steps in the evolution of face-to-face therapies to more innovative interventions. These new therapies included the use of new technologies such as virtual environments and computer-based therapies, thus providing users with a greater autonomy [Bioulac, Lallemand autonomy .The described system presented in this paper goes one step beyond, by including the use of online therapies which promote availability and convenience while using the tool. These therapies serve as a supporting tool for children and adolescents with time management and organizational problems. The development of new online solutions could help to complement traditional therapies fostering their effects and helping to create efficient management and organisational skills.Results obtained from the TMBQ show scores below 3.5 points out of 5 in every area. These results are especially low when it comes to the use of specific techniques for efficient time management skills.These results suggest the need for the creation of new, efficient, and attractive content that provides guidance and effective techniques to work on time management skills. It is therefore necessary to create an accessible tool for time management habits and the prioritising of tasks for adolescents in general, and not only for those diagnosed with ADHD.The described tool is focused on working on these activities, particularly on prioritising tasks. When analysing its usability, results were in 78.75 out of 100. Although this result means a good acceptance of the system, the authors have analysed its weaknesses in order to implement possible improvements. Segmenting participants by age shows that there are differences related to system usability and users’ comfort and confidence. Even though results were acceptable in both groups (please refer to As a conclusion to this study, it was confirmed that there is a need for new interactive content in order to work on time management skills in teenagers with and without ADHD. Key skills to be worked on lie not only in the field of the prioritisation of tasks, but also in the effective utilisation of specific techniques to that effect. Nevertheless, authors consider that this kind of adaptive tele-therapies should be adopted as a support tool for traditional therapies, not as a substitute for conventional interventions.Future directions for this study in the field of the design and development of the system are expanding the tool to include new skills, such as effective time organisation, that continues along the lines of the current tool. Moreover, the system should be adapted to be suitable for all age-ranges, trying to minimise divergences between them. Additionally, providing a greater degree of customisation to the tool may help to improve the acceptance by both age groups.With a higher number of users.With users with and without an ADHD diagnosis.With the segmentation of participants into two age groups.Developing a bilingual or trilingual tool that allows the study to be replicated in other national and international territories in where reported diagnosis of ADHD is significantly different from the Basque Country, Spain.Performing a longitudinal study on the impact of online game-based tools on time management skills in teenagers with and without ADHD.Finally, the main direction for the future is to replicate this study:The creation of a completely new tool capable of working on different skills, in conjunction with the replication of the current study, may help to understand these users’ needs and boost time management skills among teenagers with and without ADHD.