N-acetyl cysteine add-on treatment for bipolar II disorder: a subgroup analysis of a randomized placebo-controlled trial

BackgroundThe evidence base for the pharmacological treatment of bipolar II disorder is limited. In bipolar disorder, there is evidence for glutathione depletion and increased oxidative stress, as well as dysregulation of glutamate; N-acetyl cysteine (NAC) has effects on both of these systems. Add-on NAC has been shown to have a significant benefit on depressive symptoms in a randomized placebo-controlled trial. In this report, we explore the effects of this compound in a subset of patients with bipolar II disorder from that trial.MethodsIndividuals were randomized to NAC or placebo in addition to treatment as usual, in a double-blind fashion. Mood and functional outcomes were assessed up to 24 weeks of treatment.ResultsFourteen individuals were available for this report, seven in each group. Six people achieved full remission of both depressive and manic symptoms in the NAC group; this was true for only two people in the placebo group (χ2 = 4.67, p = 0.031).LimitationsSubgroup analyses in a small subsample of patients. Not all participants had elevated depression scores at baseline.ConclusionNotwithstanding all the limitations that subgroup analysis of trials carry, this data could serve as a hypothesis-generating stimulus for further clinical trials of pharmacologic treatment for bipolar II depression.