Bipolar affective disorder is one of a group of mood disorders, which also includes unipolar depression and dysthymia. Bipolar disorder has been classified into two main subtypes, bipolar I and bipolar II. It is important to diagnose patients with the correct subtype of bipolar disorder, as treatment and management differs between the two. Misdiagnosis leading to inappropriate treatment carries the risk of harm to others or suicide, most notably in patients with bipolar I. Bipolar I and bipolar II disorder can be largely thought of as similar conditions but at different poles on a spectrum of severity. In fact, a diagnosis of bipolar II disorder is sometimes amended to the more severe bipolar I disorder in a proportion of patients. This paper aims to explore the similarities and differences between the two conditions, as differentiation between the two conditions can often be difficult.
Keywords: bipolar I affective disorder, bipolar II affective disorder