Background: Fluctuations in mood are quintessential features of bipolar disorder; however, previous studies have seldom examined the extent to which pharmacotherapies for bipolar disorder may reduce or ameliorate daily or weekly mood variability. The anticonvulsant lamotrigine has demonstrated efficacy for relapse prevention in bipolar disorder, but its possible mood-stabilizing properties on a day-to-day or week-to-week basis have not previously been investigated.
Methods: Weekly mood shifts were examined over 26 weeks using patients' self-reported prospective Life Chart Method (LCM) data obtained as part of a previously reported randomized relapse prevention comparison of lamotrigine monotherapy or placebo in 182 bipolar patients with DSM-IV rapid cycling. Generalized estimating equation (GEE) analyses were used to compare treatment arms for subjects who achieved euthymia across weeks.
Results: After adjusting for potential confounding factors, a final GEE model revealed that subjects taking lamotrigine were 1.8 times more likely than those taking placebo to achieve euthymia, as measured by LCM, at least once per week over 6 months (95% confidence interval [CI] = 1.03-3.13). Subjects taking lamotrigine had an increase of .69 more days per week euthymic as compared with those taking placebo (p = .014).
Conclusions: Achievement of euthymia across weeks represents a novel paradigm shift in gauging the mood-stabilizing properties of a psychotropic agent. The present findings demonstrate the utility of the prospective Life Chart Method for assessing longitudinal mood stability during randomized clinical trials for bipolar disorder. The results lend support to the potential mood-stabilizing properties of lamotrigine monotherapy for bipolar disorder.