Introduction

As noted by Parker, management of Bipolar II Disorder is challenging for several reasons, including the scarcity of controlled data to inform evidence-based care. Such limited data mean that clinicians commonly extrapolate information regarding BP I and/or (unipolar) major depressive disorder, and view BP II as an intermediate category. Such an approach has strengths and limitations. One notable limitation is that it may underemphasise the heterogeneity of BP II, a condition with substantial inter-patient variability.

Thus, some patients with BP II may have an illness more like major depressive disorder: relatively infrequent recurrent pure (with minimal mixed features) depressive episodes, rare hypomanias, and – with antidepressants – they experience relief of depression without treatment-emergent affective switch (TEAS) into hypomania or accelerating episodes. Antidepressants may be considered foundational treatments for this presentation. In academic centres with specialty clinics, such patients are more likely referred to major depressive disorder clinics, where clinicians may view antidepressants as the treatment of choice for this type of BP II.

However, other patients with BP II may have an illness more akin to BP I. These patients experience relatively frequent recurrent depressive episodes that include mixed features (in some instances with concurrent depression and hypomania, i.e. dysphoric hypomania), common hypomanias and, in some instances, rapid cycling. Antidepressants give inadequate relief of their depression and can confer TEAS, and/or cycle acceleration. For these patients, mood stabilisers or atypical antipsychotics – not antidepressants – may be considered foundational treatments.