Bipolar disorder with childhood
attention-deficit hyperactivity disorder (
ADHD) is a subphenotype characterized by earlier age of onset, more frequent mood episodes, more suicide attempts, and more interpersonal violence than pure bipolar patients. The aim of this study was to test the
biological validity of using childhood
ADHD to subgroup
bipolar disorder. The monoamine metabolites, homovanillinic
acid (HVA), 5-hydroxyindoleacetic
acid (5-HIAA) and 3-methoxy-4-hydroxyphenylglycol (
MHPG) were determined in the cerebrospinal fluid (CSF) of 53 euthymic patients with
bipolar disorder type 1, with (N = 17) and without (N = 36) a history of childhood
ADHD. In addition to structured clinical interviews, childhood
ADHD was assessed by a next of kin using the
Autism-
Tics,
ADHD and other comorbidities questionnaire (A-TAC), and by patients themselves using the Wender Utah rating scale (WURS-25). Current
ADHD symptoms were assessed by the Brown
attention-deficit disorder scale (Brown ADD). Bipolar patients with childhood
ADHD had significantly lower CSF concentration (mean +/- SD nmol/l) of HVA (89.0 +/- 32.5 vs. 115.8 +/- 47.1, P = 0.039) and
5-HIAA (88.7 +/- 38.5 vs. 116 +/- 47.9, P = 0.021) than pure bipolar patients. CSF
MHPG did not differ between the groups. The WURS-25 score correlated negatively with both HVA (r = -0.27, P = 0.048) and
5-HIAA (r = -0.30, P = 0.027). Likewise, the Brown ADD total score correlated negatively with both HVA (r = -0.34, P = 0.013) and
5-HIAA (r = -0.35, P = 0.011). These findings indicate different monoaminergic function in patients with and without childhood
ADHD in
bipolar disorder type 1. This lends
biological support to the notion that those with childhood
ADHD represent a valid subphenotype of
bipolar disorder.