Prior stimulant treatment in adolescents with bipolar disorder: association with age at onset.

OBJECTIVES: To compare demographic and clinical characteristics between bipolar adolescents with and without a history of stimulant treatment, we hypothesized that adolescents treated with stimulants would have an earlier age at onset of bipolar disorder, independent of co-occurring attention-deficit-hyperactivity disorder (ADHD).
METHOD: Thirty-four adolescents hospitalized with mania were assessed using the Washington University at St Louis Kiddie Schedule for Affective Disorders and Schizophrenia (WASH-U-KSADS). We systematically evaluated age at onset of bipolar disorder and pharmacological treatment history.
RESULTS: Bipolar adolescents with a history of stimulant exposure prior to the onset of bipolar disorder had an earlier age at onset of bipolar disorder than those without prior stimulant exposure. Additionally, bipolar adolescents treated with at least two stimulant medications had a younger age at onset compared with those who were treated with one stimulant. There was no difference in age at onset of bipolar disorder between bipolar adolescents with and without ADHD.
CONCLUSIONS: Our results suggest that stimulant treatment, independent of ADHD, is associated with younger age at onset of bipolar disorder. A behavioral sensitization model is proposed to explain our findings. There are several limitations to our study including the small sample size, the retrospective assessment of stimulant exposure and age at onset of bipolar disorder, and the inclusion of only hospitalized patients, who may be more likely to present with a severe illness. Nonetheless, future prospective longitudinal investigations that systematically assess the effects of stimulant medications in children with or at genetic risk for bipolar disorder are warranted.