Compelling evidence in Caucasian populations suggests a role for copy-number variations (CNVs) in autism spectrum disorder (ASD) and schizophrenia (SCZ). We analyzed 1,108 ASD cases, 2,458 SCZ cases, and 2,095 controls in a Japanese population and confirmed an increased burden of rare exonic CNVs in both disorders. Clinically significant (or pathogenic) CNVs, including those at 29 loci common to both disorders, were found in about 8% of ASD and SCZ cases, which was significantly higher than in controls. Phenotypic analysis revealed an association between clinically significant CNVs and intellectual disability. Gene set analysis showed significant overlap of biological pathways in both disorders including oxidative stress response, lipid metabolism/modification, and genomic integrity. Finally, based on bioinformatics analysis, we identified multiple disease-relevant genes in eight well-known ASD/SCZ-associated CNV loci (e.g., 22q11.2, 3q29). Our findings suggest an etiological overlap of ASD and SCZ and provide biological insights into these disorders.

The autism spectrum condition (ASC) group scored significantly lower than controls on the EQ, and significantly higher on the SQ. Among both control groups, females scored significantly higher than males on the EQ, whilst males scored significantly higher than females on the SQ. The distribution of 'brain types', based on the difference between EQ and SQ scores, showed distinct profiles for people with ASC, control males and control females.

Although the DSM-IV diagnostic criteria for Attention Deficit/Hyperactivity Disorder (AD/HD) exclude Pervasive Developmental Disorder (PDD), some clinicians find that the two disorders can be comorbid and, in fact, make a dual diagnosis. Nevertheless, few empirical studies have investigated the clinical necessity for this practice. In the first of our two studies, children with high-functioning PDD were selected from among 520 outpatients. Of these, children also meeting the DSM-IV criteria for AD/HD were identified through a psychologist's observation, the completion of the ADHD-Rating Scale by parents and/or teachers, and a child psychiatrist's examination. We then examined the impact of PDD subtype and age on the co-occurrence rate. Study 2 analyzed comorbidity in two cases taken from Study 1. Of the 53 subjects in Study 1, 36 children also met the DSM-IV criteria for AD/HD. The co-occurrence rate for Asperger's Disorder (AS)/Pervasive Developmental Disorder, Not Otherwise Specified (PDDNOS) (85%) was significantly higher than for Autistic Disorder (57.6 %), and AD/HD symptoms were more common in younger children. Study 2 demonstrated the existence of comorbidity of PDD and AD/HD as separate disorders. We conclude not only that AD/HD symptoms occur frequently in children with PDD, but also that in some cases a dual diagnosis is essential to the implementation of effective treatment.

In the current study, the child AQ was administered in Japan, to examine whether the UK results for reliability and validity generalize to a different culture. Assessment groups were: Group 1: n = 81 children with Asperger Syndrome (AS) or high-functioning autism (HFA); Group 2: n = 22 children diagnosed PDD-NOS with average IQ; and Group 3: n = 372 randomly selected controls from primary and secondary schools. Both clinical groups scored significantly higher than controls (AS/HFA mean AQ = 31.9, SD = 6.93; PDD-NOS mean AQ = 28.0, SD = 6.88; controls mean AQ = 11.7, SD = 5.94). Among the controls, males scored significantly higher than females. The pattern of difference between clinical groups and controls was found to be similar in both countries.

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