Bipolar disorders are mood disorders characterised by manic (bipolar I disorder,) or hypomanic episodes and major depressive episodes (bipolar II disorder). These have been reworked into the model of bipolar spectrum disorder, where manic symptom load increases from unipolar depression to bipolar II to bipolar I. In this article we consider the fMRI findings for bipolar I, bipolar II and major depressive disorder (MDD) and conclude that bipolar disorder and MDD do not share the same pattern of neural disturbance. The distinction between bipolar I and bipolar II is less clear, as the data is still preliminary in nature, but the two disorders appear to share a similar pattern of brain activity. This fMRI data suggests that the bipolar spectrum model still requires refining, but provides a useful framework upon which to base future research into affective disorders.
Keywords: bipolar disorder, mood disorders, bipolar spectrum, fMRI, neuroimaging