ADHD is the most frequent comorbidity of FASD but the exact relationship between the two entities is not well defined. There is some evidence that a specific clinical subtype of ADHD occurs in FASD, with earlier onset and a different response to medication. However, the relationship between ADHD and FASD may be coincidental, may reflect a common etiologic pathway, or may reflect the frequent genetic origin of ADHD and its prevalence in the general population. It is likely that a range of these etiologic factors account for ADHD in FASD, resulting in a heterogeneous population, which makes it difficult to replicate or generalize findings across studies.
