In the last decade several authors have investigated the co- morbidity of ADHD in ASD population. Concurrent diagnosis of ADHD and PDD is not allowed in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV). Although differences in ADHD subtypes among PDD and non PDD samples have been investigated previously, fewer studies have done comparisons with ADHD population.
Objectives: To investigate ADHD subtypes in a large ASD and ADHD clinical population.
Methods: Children admitted to the outpatient developmental behavioral Clinic of Psychiatric Hospital Dr. Juan N. Navarro were recruited for this study. Measures: ADI-R routinely performed to this population was use as gold standard diagnosis. A semi structured interview was conducted to assign subtypes for ASD (Autism, Asperger and PDDNOS) and ADHD DSM-IV diagnosis (Inattentive, Combined and Hyperactive-Impulsive). These interviews were done by senior board certified child psychiatrist LAG.
The study sample consisted of 218 children aged 2-17 years old (M 7.68, SD 3.29), 82.6% were masculine. Within this sample 50.5% of the children (n=110) were diagnosed with Autism, (15.1%) were Asperger (n=33) and 6% had PDDNOS (n=13). The Non ASD sample 28.4% (n=62) was identified as ADHD. The ADHD prevalence in the ASD sample was 80.01% which was higher for Autism 81.8% and Asperger 78.8% compared to PDDNOS 69.2% but differences were non- significant (p=.54). In the ADHD sample, 31children (50.0%) had the inattentive type, 27 (43.5%) had the combined type and 4 (6.5%) had the hyperactive-impulsive type of ADHD. Subtypes prevalence between ASD and ADHD sample was very similar. Through multinomial logistic regression the risk for ADHD was higher for autism OR 2.0 (CI 95% 0.56-7.00).14 and for Asperger OR 1.61 (CI 95% 0.39-6.99) although non-significant.
These results show that ADHD prevalence is higher in ASD samples. The subtype pattern of prevalence in ASD is similar to ADHD clinical samples.
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