To the Editor: The clinical case conference by Jean A. Frazier, M.D., et al. (1) highlighted that diagnosing comorbid bipolar disorder in patients with Asperger’s disorder who display prominent affective symptoms is crucial so that these children can receive appropriate treatment. However, this is not a new observation and has already been made by me in a previous report (2). In addition to increasing awareness of the existence of such comorbidity in patients with Asperger’s disorder, I emphasized caution in prescribing psychotropic medications—especially antidepressants—to this population. Antidepressants, including selective serotonin reuptake inhibitors (SSRIs), have been shown to induce hypomania in some patients with Asperger’s disorder (3) and also to worsen aggressive behavior—the latter evident in the case study by Dr. Frazier and colleagues. Thus, when antidepressants are added to treat depression or repetitive stereotyped behavior in such patients, it may be worthwhile to add a mood stabilizer, particularly if there is a positive family history of affective illness.