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Objective: The Quantified Behavioral Test (QbTest) is a computerized diagnostic test for ADHD, used in clinical psychiatric care, but its validity may be questioned. We analyzed the QbTest's diagnostic validity and its relation to cognitive ability and psychosocial factors in an adolescent population with a high occurrence of neurodevelopmental disorders. Method: In total, 340 participants aged 15 years, completed the QbTest, along with questionnaires, clinical and intelligence quotient (IQ) assessments. Results: The clinical assessment resulted in 89 (26%) participants with ADHD. Area under curve (AUC) scores indicated a random to poor validity of the QbTest (AUC range = 0.48-0.64). QbTest scores of inattention and impulsivity correlated with IQ. Conclusion: The QbTest was insufficient as a diagnostic test for ADHD, and was not able to differentiate ADHD from other neurodevelopmental conditions. Clinicians should be aware of the dubious discriminating power of the QbTest. [ABSTRACT FROM AUTHOR]

Previous research has found a complex relationship between psychopathic traits, neurodevelopmental problems (NDPs), and conduct disorder (CD) in children. This study explores associations between psychopathic traits, assessed with the Child Problematic Traits Inventory—Short Version (CPTI-SV), and CD in children with and without coexisting NDPs (i.e., attention deficit/hyperactivity disorder [ADHD] and autism spectrum disorder [ASD]) in a community-based sample of Swedish twins (n = 8762). Findings indicate weak to moderately strong correlations between psychopathic traits and CD, ADHD, and ASD, respectively. Furthermore, in univariable analyses, both psychopathic traits and NDPs displayed significant positive associations with being screened positive for CD, though only the grandiose-deceitful dimension of CPTI-SV and the ADHD domain concentration and attention deficits remained significantly associated with CD in a multivariable regression model. The results are relevant to screening and assessment in child and youth psychiatry, as a grandiose and deceitful interpersonal style may also be a valid sign of children at risk of developing CD. [ABSTRACT FROM AUTHOR]

Background: Reliable and easy to administer screening instruments focusing on neurodevelopmental disorders and associated conditions are scarce. The Autism-Tics, AD/HD and other Comorbidities inventory (A-TAC) has previously been validated and reporting good-excellent validity for several disorders. This article aims to expand these findings by including more conditions in a substantially larger sample augmented with the Swedish National Patient Register (NPR). Methods: Since 2004 parents of all 9-year-old Swedish twins have been invited to participate in a telephone interview in the Child and Adolescent Twin Study in Sweden, CATSS. The CATSS is linked to the NPR which includes data from in- and outpatient care. Data on neurodevelopmental disorders (A-TAC) collected in CATSS were compared with diagnoses from the NPR. We investigated diagnoses that had been made both before (previous validity) and after (predictive validity) the interview. Results: Sensitivity and specificity of A-TAC scores for predicting earlier or later clinical diagnoses were mostly good-excellent, with values of the area under the curve for a clinical diagnosis of autism spectrum disorder (ASD) of .98, attention deficit hyperactivity disorder (ADHD) .93, learning disorder (LD) .92, and oppositional defiant disorder (ODD) .99, with small differences in terms of previous and predictive analyses. A-TAC provided little validity for eating disorders. Conclusion: The result support previous claims: A-TAC is a broad screening instrument with a particular strength in assessing ASD, ADHD, LD, and ODD at ages 9 and 12, and also provides phenotypic information about other child psychiatric disorders. [ABSTRACT FROM AUTHOR]

Neurodevelopmental disorders (Attention-Deficit/Hyperactivity Disorder (ADHD), Autism Spectrum Disorder (ASD), tic disorder, intellectual disability (ID)), in prison populations have received increased attention but the focus has generally been on one single condition leaving out the global picture. This study assessed the prevalence and overlap of neurodevelopmental disorders (NDD) in a consecutive cohort (n=270) of young adult male offenders (age 18–25 years), sentenced for “hands-on” violent offences and serving prison time in Swedish prisons. Seventy-one percent of all who met inclusion criteria participated. Comprehensive clinical assessments were carried out including history of early antisocial behavior and maladjustment, self-report questionnaires and an intelligence test. Sixty-three percent of the study group met DSM-IV criteria for childhood ADHD, 43% for ADHD in adulthood, 10% met criteria for an ASD, 6% for Tourette syndrome, and 1% for ID. Twenty-two percent had borderline intellectual functioning. A substantial rate of overlap between the NDDs was found. The combined NDD group had an earlier onset of antisocial behavior, had more aggressive behavior and lower school achievements than the non-NDD group. The results highlight the need for prison and probation services to be attentive of and screen for neurodevelopmental disorders in young violent offenders. [ABSTRACT FROM AUTHOR]

The Child and Adolescent Twin Study in Sweden (CATSS) is an ongoing longitudinal twin study targeting all twins born in Sweden since July 1, 1992. Since 2004, parents of twins are interviewed regarding the children's somatic and mental health and social environment in connection with their 9th or 12th birthdays (CATSS-9/12). By January 2010, 8,610 parental interviews concerning 17,220 twins had been completed, with an overall response rate of 80%. At age 15 (CATSS-15) and 18 (CATSS-18), twins and parents complete questionnaires that, in addition to assessments of somatic and mental health, include measures of personality development and psychosocial adaptation. Twin pairs in CATSS-9/12 with one or both twins screening positive for autism spectrum disorders, attention deficit/hyperactivity disorder, tic disorders, developmental coordination disorder, learning disorders, oppositional defiant disorder, conduct disorder, obsessive–compulsive disorder, and/or eating problems have been followed with in-depth questionnaires on family, social environment and personality, and subsequently by clinical assessments at age 15 together with randomly selected population controls, including 195 clinically assessed twin pairs from the first 2 year cohorts (CATSS-15/DOGSS). This article describes the cohorts and study groups, data collection, and measures used. Prevalences, distributions, heritability estimates, ages at onset, and sex differences of mental health problems in the CATSS-9/12, that were analyzed and found to be overall comparable to those of other clinical and epidemiological studies. The CATSS study has the potential of answering important questions on the etiology of childhood mental health problems and their role in the development of later adjustment problems. [ABSTRACT FROM PUBLISHER]

Background: Reliable, valid and easily administered screening instruments would greatly facilitate large-scale neuropsychiatric research.Aims: To test a parent telephone interview focused on autism - tics, attention-deficit hyperactivity disorder (ADHD) and other comorbidities (A-TAC).Method: Parents of 84 children in contact with a child neuropsychiatric clinic and 27 control children were interviewed. Validity and interrater and test - retest reliability were assessed.Results: Interrater and test - retest reliability were very good. Areas under receiver operating characteristics curves between interview scores and clinical diagnoses were around 0.90 for ADHD and autistic spectrum disorders, and above 0.70 for tics, learning disorders and developmental coordination disorder. Using optimal cut-off scores for autistic spectrum disorder and ADHD, good to excellent kappa levels for interviews and clinical diagnoses were noted.Conclusions: The A-TAC appears to be a reliable and valid instrument for identifying autistic spectrum disorder, ADHD, tics, learning disorders and developmental coordination disorder. [ABSTRACT FROM AUTHOR]

Objective: Neurodevelopmental problems (NDPs) may influence the transition from childhood to adolescence. Our aim was to study long-term psychosocial outcomes of NDPs, focusing on ADHD. Method: Data was collected through a telephone interview with parents of twins at ages 9 or 12 years. NDP screen-positive children were clinically assessed at age 15; N = 450. Psychosocial outcome concerning peers, school, internalizing problems, antisocial behavior, alcohol misuse, drug misuse, and impaired daily functioning was examined. Results: Even after controlling for other NDP comorbidity, screen-positivity for ADHD doubled or tripled the odds of later psychosocial problems. When controlling for parental education level, the significant effect of ADHD remained only for antisocial behavior and impaired daily functioning. Conclusions: Signs of NDPs as well as other psychiatric diagnoses at ages 9 or 12 years are associated with a more problematic adolescence. However, despite the presence of comorbidity, early ADHD symptoms stand out as the most important risk factor for later antisocial development and impaired daily functioning. [ABSTRACT FROM AUTHOR]

Background Studies have found an association between low birth weight and ADHD, but the nature of this relation is unclear. First, it is uncertain whether birth weight is associated with both of the ADHD dimensions, inattentiveness and hyperactivity-impulsivity. Second, it remains uncertain whether the association between birth weight and ADHD symptom severity is confounded by familial factors. Method Parents of all Swedish 9- and 12-year-old twins born between 1992 and 2000 were interviewed for DSM- IV inattentive and hyperactive-impulsive ADHD symptoms by the Autism - Tics, AD/ HD and other Comorbidities (A- TAC) inventory ( N = 21,775 twins). Birth weight was collected prospectively through the Medical Birth Registry. We used a within-twin pair design to control for genetic and shared environmental factors. Results Reduced birth weight was significantly associated with a mean increase in total ADHD (β = −.42; 95% CI: −.53, −.30), inattentive (β = −.26; 95% CI: −.33, −.19), and hyperactive-impulsive (β = −.16; 95% CI: −.22, −.10) symptom severity. These results imply that a change of one kilogram of birth weight corresponded to parents rating their child nearly one unit higher (going from 'no' to 'yes, to some extent' on a given symptom) on the total ADHD scale. These associations remained within pairs of MZ and DZ twins, and were also present when restricting the analyses to full term births. Conclusions There is an independent association between low birth weight and all forms of ADHD symptoms, even after controlling for all environmental and genetic confounds shared within twin pairs. These results indicate that fetal growth restriction (as reflected in birth weight differences within twin pairs) and/or the environmental factors which influence it is in the casual pathway leading to ADHD. [ABSTRACT FROM AUTHOR]

Background: Despite increasing knowledge of attention deficit hyperactivity disorder (ADHD) across the life span, there is still little research on adults' own experiences of being diagnosed with ADHD. The aim of the present study was to explore and describe patients' experiences and perceptions of being diagnosed with ADHD in adulthood. The study can be seen as an attempt to validate the diagnosis from a patient perspective. Methods: Twenty-one adults diagnosed with ADHD were individually interviewed. The interviews were open-ended and exploratory, analysed with a qualitative phenomenographical approach, and the results were described in categories. Results: Positive experiences were dominant, but there was a complex intra- and inter-individual variation of experiences. Descriptions focused on the diagnosis, on identity, and on life. The diagnosis was described as explaining a previously inexplicable life history, but was also questioned, both as a phenomenon and in relation to the individual (the diagnosis in focus). It was experienced as providing self-knowledge and increased value, but could also cause devaluation and concern about identity (identity in focus). It meant help to achieve a better life, but was also perceived to restrict possibilities and cause disappointment over lack of professional help. It could lead to a wish for an earlier diagnosis that could have spared suffering, as well as to a changed view of the participants' relatives (life in focus). All but one of the interviewees expressed important positive consequences of being diagnosed with ADHD. About half of them acknowledged negative aspects of being diagnosed, but none regretted going through the neuropsychiatric evaluation. Conclusions: From a patient perspective, there are major positive consequences of being diagnosed with ADHD, compared to the undiagnosed situation. Knowledge of the individual's combination of experiences is important for professionals, as these experiences can affect well-being and interfere with treatment. Negative experiences in particular might need to be addressed in the treatment work. [ABSTRACT FROM AUTHOR]

Background: Recent studies have reported associations between air pollution exposure and neurodevelopmental disorders in children, but the role of pre- and postnatal exposure has not been elucidated. Aim: We aimed to explore the risk for autism spectrum disorders (ASD) and attention-deficit hyperactivity disorder (ADHD) among children in relation to pre- and postnatal exposure to air pollution from road traffic. Methods: Parents of 3,426 twins born in Stockholm during 1992–2000 were interviewed, when their children were 9 or 12 years old, for symptoms of neurodevelopmental disorders. Residence time-weighted concentrations of particulate matter with a diameter <10 μm (PM10) and nitrogen oxides (NOx) from road traffic were estimated at participants’ addresses during pregnancy, the first year, and the ninth year of life using dispersion modeling, controlling for seasonal variation. Multivariate regression models were used to examine the association between air pollution exposure and neurodevelopmental outcomes, adjusting for potential confounding factors. Results: No clear or consistent associations were found between air pollution exposure during any of the three time windows and any of the neurodevelopmental outcomes. For example, a 5–95% difference in exposure to NOx during pregnancy was associated with odds ratios (ORs) of 0.92 (95% confidence interval (CI): 0.44–1.96) and 0.90 (95% CI: 0.58–1.40) for ASD and ADHD respectively. A corresponding range in exposure to PM10 during pregnancy was related to ORs of 1.01 (95% CI: 0.52–1.96) and 1.00 (95% CI: 0.68–1.47) for ASD and ADHD. Conclusions: Our data do not provide support for an association between pre- or postnatal exposure to air pollution from road traffic and neurodevelopmental disorders in children. [ABSTRACT FROM PUBLISHER]

Introduction: The study of differences between monozygotic (MZ) twin pairs with respect to ADHD may provide novel leads to disentangle the environmental contribution driving its phenotypes. Objectives: To examine non-shared environmental influences on executive function in dimensionally defined ADHD. Methods: This study included 27 MZ twin pairs (7 female) aged 11–20 years being moderately to substantially discordant for ADHD traits as assessed by the Attention Problem (AP) scale of the Child Behavior Checklist/Adult Behavior Checklist. The twins completed the Wisconsin Card Sorting Test (WCST) for cognitive flexibility and the Tower Test (TT) for foresighted planning. Two statistical approaches were used to analyze the data. First, correlations between ADHD trait intra-pair differences and WCST and TT scores were calculated. Second, the significance of those intra-pair differences on WCST and TT, using ADHD as categorical variable in clinically discordant pairs, was tested. Results: Both analysing strategies revealed a link between ADHD on one hand, and foresighted planning and inhibitory control on the other hand mediated by non-shared environmental factors. The first statistical approach yielded positive correlations between intra-pairs differences on the AP scale and intra-pair differences on two subscales of the TT: total rule violation (rs = 0·41) and rule-violation-per-item-ratio (rs = 0·38). Findings in categorically discordant pairs were consistent, showing within-pair differences on the same subtests (z-1·63, P = 0·05, one-tailed and z = −1·60, P = 0·05, one-tailed). Conclusions: Findings confirm previous research suggesting ADHD to be a quantitative extreme on a continuum with executive functions being a cognitive marker of ADHD traits. Non-shared environmental factors appear to influence planning skills and inhibitory control. [ABSTRACT FROM AUTHOR]

Autism spectrum disorders (ASD) and attention deficit hyperactivity disorder (ADHD) show high comorbidity. The following questions were addressed regarding their specific symptoms: What is the factor structure of ASD and ADHD symptoms, to what degree do different symptom domains cluster together, to what extent are these domains caused by the same genetic and environmental influences, and what is the best model of their co-occurrence? A population-based twin cohort of over 17,000 9- and 12-year-olds were assessed using the Autism-Tics, AD/HD, and other Comorbidities parental interview inventory. Principal component analyses were conducted, and symptom domain clustering was assessed. Four multivariate twin models were compared. Factors split into three ASD (social impairments, communication impairments, and restricted repetitive behaviors and interests), and three ADHD (inattention, hyperactivity, and impulsivity) symptom domains. Some ASD-ADHD symptom domain combinations clustered together often, although others not at all. A two-factor common pathway model fit the data, suggesting that ASD and ADHD symptom domains tap into separate "ASD" and "ADHD" latent factors that showed high genetic overlap. All subdomains also showed significant specific genetic and environmental influences, reflecting the etiological heterogeneity both within and between ASD and ADHD. These flndings support the conceptual distinction of ASD and ADHD, and demonstrate the considerable natural co-occurrence of particular ASD/ADHD symptom domains. The results imply that more children with 1 condition shov/ features of the other condition than show complete comorbidity. Emphasis on symptom co-occurrence, rather than complete comorhidity between disorders, may help focus clinical approaches and advance molecular genetic research. [ABSTRACT FROM AUTHOR]

The Autism-Tics, AD/HD, and other Comorbidities (A-TAC) inventory is used in epidemiological research to assess neurodevelopmental problems and coexisting conditions. Although the A-TAC has been applied in various populations, data on retest reliability are limited. The objective of the present study was to present additional reliability data. The A-TAC was administered by lay assessors and was completed on two occasions by parents of 400 individual twins, with an average interval of 70 days between test sessions. Intra- and inter-rater reliability were analysed with intraclass correlations and Cohen's κ A-TAC showed excellent test-retest intraclass correlations for both autism spectrum disorder and attention deficit hyperactivity disorder (each at .84). Most modules in the A-TAC had intra-and inter-rater reliability intraclass correlation coefficients of ≥ .60. Cohen's κ indicated acceptable reliability. The current study provides statistical evidence that the A-TAC yields good test-retest reliability in a population-based cohort of children. [ABSTRACT FROM AUTHOR]

Melatonin is a powerful antioxidant and a synchronizer of many physiological processes. Alteration in melatonin signaling has been reported in a broad range of diseases, but little is known about the genetic variability of this pathway in humans. Here, we sequenced all the genes of the melatonin pathway - AA-NAT, ASMT, MTNR1A, MTNR1B and GPR50 - in 321 individuals from Sweden including 101 patients with attention-deficit/hyperactivity disorder (ADHD) and 220 controls from the general population. We could find several damaging mutations in patients with ADHD, but no significant enrichment compared with the general population. Among these variations, we found a splice site mutation in ASMT (IVS5+2T>C) and one stop mutation in MTNR1A (Y170X) - detected exclusively in patients with ADHD - for which biochemical analyses indicated that they abolish the activity of ASMT and MTNR1A. These genetic and functional results represent the first comprehensive ascertainment of melatonin signaling deficiency in ADHD. [ABSTRACT FROM AUTHOR]

Many international studies show that adolescents in coercive institutional care display high prevalences of mental disorders, especially in the form of disruptive behavior disorders [including attention-deficit/hyperactivity disorder (AD/HD), oppositional defiant disorder, and conduct disorder], anxiety disorders, and mood disorders. High degrees of overlap across mental disorders have also been reported. In addition, institutionalized adolescents are often traumatized. Despite this well-documented psychiatric morbidity, the mental health care needs of detained adolescents are often overlooked. The main objective of this study is to assess prevalences of psychiatric disorders, results of intelligence tests, and previous contacts with child and adolescent psychiatric services among adolescents in institutional care. DSM-IV diagnoses, mental health contacts, substance abuse, neurocognitive abilities, and school performance were registered in 100 adolescents (92 boys, 8 girls) aged 12-19 years (mean age 16.0; SD ± 1.5) consecutively committed to Swedish juvenile institutions between 2004 and 2007. At least one psychiatric disorder was diagnosed in 73% of the subjects: 48% met DSM-IV diagnostic criteria for AD/HD, 17% for an autism spectrum disorder, and 10% for a mental retardation. The collapsed prevalence for psychiatric disorders requiring specialist attention was 63%. Our data indicate that systematic diagnostic procedures are crucial in the treatment planning for institutionalized adolescents. Adequate treatment strategies need to be designed and implemented to meet the extensive mental health care needs of this vulnerable population. [ABSTRACT FROM AUTHOR]

Background: Reliable, valid, and easy-to-administer instruments to identify possible caseness and to provide proxies for clinical diagnoses are needed in epidemiological research on child and adolescent mental health. The aim of this study is to provide further validity data for a parent telephone interview focused on Autism - Tics, Attention-deficit/hyperactivity disorder (AD/HD), and other Comorbidities (A-TAC), for which reliability and preliminary validation data have been previously reported. Methods: Parents of 91 children clinically diagnosed at a specialized Child Neuropsychiatric Clinic, 366 control children and 319 children for whom clinical diagnoses had been previously assigned were interviewed by the ATAC over the phone. Interviewers were blind to clinical information. Different scores from the A-TAC were compared to the diagnostic outcome. Results: Areas under ROC curves for interview scores as predictors of clinical diagnoses were around 0.95 for most disorders, including autism spectrum disorders (ASDs), attention deficit/hyperactivity disorder (AD/HD), tic disorders, developmental coordination disorders (DCD) and learning disorders, indicating excellent screening properties. Screening cut-off scores with sensitivities above 0.90 (0.95 for ASD and AD/HD) were established for most conditions, as well as cut-off scores to identify proxies to clinical diagnoses with specificities above 0.90 (0.95 for ASD and AD/HD). Conclusions: The previously reported validity of the A-TAC was supported by this larger replication study using broader scales from the A-TAC-items and a larger number of diagnostic categories. Short versions of algorithms worked as well as larger. Different cut-off levels for screening versus identifying proxies for clinical diagnoses are warranted. Data on the validity for mood problems and oppositional defiant/conduct problems are still lacking. Although the A-TAC is principally intended for epidemiological research and general investigations, the instrument may be useful as a tool to collect information in clinical practice as well. [ABSTRACT FROM AUTHOR]

Objective: The authors describe personality development and disorders in relation to symptoms of attention deficit hyperactivity disorder (ADHD) and autism spectrum disorders. Method: Consecutive adults referred for neuropsychiatric investigation (N=240) were assessed for current and lifetime ADHD and autism spectrum disorders and completed the Temperament and Character Inventory. In a subgroup of subjects (N=174), presence of axis II personality disorders was also assessed with the Structured Clinical Interview for DSM-IV Personality Disorders (SCI D-l I). Results: Patients with ADHD reported high novelty seeking and high harm avoidance. Patients with autism spectrum disorders reported low novelty seeking, low reward dependence, and high harm avoidance. Character scores (self-directedness and cooperativeness) were extremely low among subjects with neuropsychiatric disorders, indicating a high overall prevalence of personality disorders, which was confirmed with the SCID-II. Cluster B personality disorders were more common in subjects with ADHD, while cluster A and C disorders were more common in those with autism spectrum disorders. The overlap between DSM-IV personality disorder categories was high, and they seem less clinically useful in this context. Conclusions: ADHD and autism spectrum disorders are associated with specific temperament configurations and an increased risk of personality disorders and deficits in character maturation. [ABSTRACT FROM AUTHOR]

The objective of the study was to explore the possibility of common signs and symptoms of childhood-onset neuropsychiatric disorders and personality disorders, especially psychopathy, in a cohort of violent offenders. A structured neuropsychiatric status comprising features recorded in childhood-onset neuropsychiatric disorders and adult personality disorders was assessed in 89 perpetrators of severe crimes against other persons, analysed for factor structure, and compared to clinical diagnostics of neuropsychiatric disorders and independent assessments of psychopathy rated by the Psychopathy Checklist Revised (PCL-R). One or several childhood-onset neuropsychiatric disorders [autism, attention-deficit/hyperactivity disorder (AD/HD), tics and learning disability] affected the majority of adult offenders. A factor analysis yielded four higher-order problem constellations: Executive Dysfunction, Compulsivity, Social Interaction Problems and Superficiality. All four constellations were positively correlated with life histories of aggression, stressing the clinical importance of these problems in adult forensic psychiatry. Compulsivity and Social Interaction Problems were associated with autistic traits and tics, Executive Dysfunction with AD/HD, conduct disorder and psychopathic as well as autistic traits. Superficiality was a distinct aspect of AD/HD and psychopathic traits, especially the PCL-R factor reflecting interpersonal callousness. Neuropsychiatric disorders and personality disorders such as psychopathy share common symptoms. The various facets of psychopathy are associated with executive dysfunction and empathy deficits with superficial understanding of self, others and the rules of communication. [ABSTRACT FROM AUTHOR]

This 3-year follow-up study compares background variables, extent of criminality and criminal recidivism in the form of all court convictions, the use of inpatient care, and number of early deaths in Swedish institutionalized adolescents (N=100) with comorbid substance use disorders (SUD) and Attention-Deficit/Hyperactivity Disorder (ADHD) (n=25) versus those with SUD but no ADHD (n=30), and those without SUD (n=45). In addition it aims to identify whether potential risk factors related to these groups are associated with persistence in violent criminality. Results showed almost no significant differences between the three diagnostic groups, but the SUD plus ADHD group displayed a somewhat more negative outcome with regard to criminality, and the non-SUD group stood out with very few drug related treatment episodes. However, the rate of criminal recidivism was strikingly high in all three groups, and the use of inpatient care as well as the number of untimely deaths recorded in the study population was dramatically increased compared to a age matched general population group. Finally, age at first conviction emerged as the only significant predictor of persistence in violent criminality with an AUC of .69 (CI (95%) .54-.84, p=.02). Regardless of whether SUD, with or without ADHD, is at hand or not, institutionalized adolescents describe a negative course with extensive criminality and frequent episodes of inpatient treatment, and thus requires a more effective treatment than present youth institutions seem to offer today. However, the few differences found between the three groups, do give some support that those with comorbid SUD and ADHD have the worst prognosis with regard to criminality, health, and untimely death, and as such are in need of even more extensive treatment interventions. [ABSTRACT FROM AUTHOR]

• Boys with a diagnosis of autism have a higher raw mean score than girls. • Girls with autism deviate further away from the sex-specific mean than boys. • Some girls with autism may not be captured by the use of existing cut-off values. Autism spectrum disorder (ASD) is diagnosed more often in boys than girls. Here, we compared the degree of autism - and related disorders - symptomatology in boys and girls with a registered diagnosis of ASD. We used parent telephone interview A-TAC (Autism-Tics, ADHD and other Comorbidities) ratings of 30,392 twins aged 9 or 12 (including 308 boys and 122 girls with National Patient Register diagnoses of ASD) participating in the Child and Adolescent Twin Study in Sweden. We used z -scores for ASD-symptoms, standardized separately for boys and girls. Boys with a diagnosis of ASD had a higher raw mean score than girls with a diagnosis on the A-TAC ASD domain. However, utilizing the z -scores, girls with a diagnosis of ASD deviated further away from the female population mean than did the boys with ASD from the male population mean. Girls also had higher standardized mean values for symptoms of Attention-Deficit/Hyperactivity Disorder, Learning Disabilities and Oppositional Defiant Disorder. The findings suggest that girls diagnosed with autism may represent an even more extreme end of the female population autistic features distribution, than diagnosed boys from the male population autistic features distribution. Future studies may benefit from examining the use of sex-specific cut-off scores. [ABSTRACT FROM AUTHOR]

Objective: Attention-deficit/hyperactivity disorder (ADHD) is more frequent in males than in females. The "female protective effect" posits that females undergo greater exposure to etiological factors than males in order to develop ADHD, leading to the prediction that relatives of females with ADHD will display more ADHD behaviors. We thus tested whether cotwins of females displaying extreme ADHD traits would display more ADHD traits than cotwins of males displaying extreme ADHD traits.Method: Parents of approximately 7,000 pairs of nonidentical twins in Sweden, and approximately 4,000 pairs of twins in England and Wales, completed dimensional assessments of ADHD traits. Probands were selected on the basis of scoring within the highest 10% of the distribution in each sample. Dimensional scores of cotwins of probands, as well as the categorical recurrence rate, were investigated by proband sex.Results: Cotwins of female probands displayed higher mean ADHD trait scores (mean = 0.62-0.79) than cotwins of male probands (mean = 0.38-0.55) in both samples. This trend was significant in the Swedish sample (p < .01) and when the 2 samples were merged into a single, larger sample (p < .001). When the samples were merged, there was also a significant association between proband sex and cotwin's categorical status, with more cotwins of female probands also being probands than cotwins of male probands.Conclusion: These findings support a female protective effect against ADHD behaviors, suggesting that females require greater exposure to genetic and environmental factors associated with ADHD in order to develop the condition. [ABSTRACT FROM AUTHOR]