Head circumference and height in autism: a study by the Collaborative Program of Excellence in Autism.

Data from 10 sites of the NICHD/NIDCD Collaborative Programs of Excellence in Autism were combined to study the distribution of head circumference and relationship to demographic and clinical variables. Three hundred thirty-eight probands with autism-spectrum disorder (ASD) including 208 probands with autism were studied along with 147 parents, 149 siblings, and typically developing controls. ASDs were diagnosed, and head circumference and clinical variables measured in a standardized manner across all sites. All subjects with autism met ADI-R, ADOS-G, DSM-IV, and ICD-10 criteria. The results show the distribution of standardized head circumference in autism is normal in shape, and the mean, variance, and rate of macrocephaly but not microcephaly are increased. Head circumference tends to be large relative to height in autism. No site, gender, age, SES, verbal, or non-verbal IQ effects were present in the autism sample. In addition to autism itself, standardized height and average parental head circumference were the most important factors predicting head circumference in individuals with autism. Mean standardized head circumference and rates of macrocephaly were similar in probands with autism and their parents. Increased head circumference was associated with a higher (more severe) ADI-R social algorithm score. Macrocephaly is associated with delayed onset of language. Although mean head circumference and rates of macrocephaly are increased in autism, a high degree of variability is present, underscoring the complex clinical heterogeneity of the disorder. The wide distribution of head circumference in autism has major implications for genetic, neuroimaging, and other neurobiological research.

Comorbid psychiatric disorders in children with autism: interview development and rates of disorders.

The Kiddie Schedule for Affective Disorders and Schizophrenia was modified for use in children and adolescents with autism by developing additional screening questions and coding options that reflect the presentation of psychiatric disorders in autism spectrum disorders. The modified instrument, the Autism Comorbidity Interview-Present and Lifetime Version (ACI-PL), was piloted and frequently diagnosed disorders, depression, ADHD, and OCD, were tested for reliability and validity. The ACI-PL provides reliable DSM diagnoses that are valid based on clinical psychiatric diagnosis and treatment history. The sample demonstrated a high prevalence of specific phobia, obsessive compulsive disorder, and ADHD. The rates of psychiatric disorder in autism are high and are associated with functional impairment.

Temporal lobe, autism, and macrocephaly.

BACKGROUND AND PURPOSE: Because of increased prevalence of macrocephaly in autism, head size must be controlled for in studies that examine volumetric findings of the temporal lobe in autistic subjects. We prospectively examined temporal lobe structures in individuals with autism who were normocephalic or macrocephalic (head circumference > 97th percentile) and in control subjects who were normocephalic or macrocephalic or who had a reading disorder (unselected for head size). The rationale for the reading disorder group was to have control subjects with potential temporal lobe anomalies, but who were not autistic. METHODS: In individuals aged 7-31 years, autism was diagnosed on the basis of standardized interview and diagnostic criteria. Control subjects ranged in age from 7 to 22 years. All subjects were male. MR morphometrics of the major temporal lobe structures were based on ANALYZE segmentation routines, in which total brain volume and total intracranial volume (TICV) were calculated. Both group comparisons and developmental analyses were performed. RESULTS: No distinct temporal lobe abnormalities of volume were observed once head size (TICV) was controlled for. In autistic and control subjects, robust growth patterns were observed in white and gray matter that differed little between the groups. Although subtle differences were observed in some structures (ie, less white matter volume in the region of the temporal stem and overall temporal lobe), none was statistically significant. CONCLUSION: No major volumetric anomalies of the temporal lobe were found in cases of autism when IQ, TICV, and age were controlled. Temporal lobe abnormalities that may be associated with autism are likely to be more related to functional organization within the temporal lobe than to any gross volumetric difference.

Autism, regression, and the broader autism phenotype.

The broader autism phenotype (BAP) is a subclinical set of personality and other features that is thought to index familiality and/or genetic liability to autism. Eighteen parents of autistic probands with a history of language regression and 70 parents of autistic probands without regression were assessed for features of the BAP and compared with published rates in parents of nonautistic subjects. Parents of probands with regressive and nonregressive autism demonstrated similar rates of the BAP (27.8% vs. 32.9%; P = 0.33). The rate of the BAP was significantly higher in both groups of autism parents than in parents of nonautistic subjects (P < or = 0.01). Thus, this measure of genetic liability is increased equally in families with both forms of autism when compared with controls. Environmental events are therefore unlikely to be the sole cause of regressive autism in our sample. Environmental events, however, may act in an additive or "second-hit" fashion in individuals with a genetic vulnerability to autism.