Bipolar disorder is a complex condition that has an early age of onset. The peak rate of onset is between the ages of 15 and 19 years, with prevalence similar in both sexes. 

Bipolar patients have between 10 and 20 years premature mortality, partly due to cardiovascular disease (driven by weight gain) but also suicide, which is among the highest for any psychiatric disorder. Approximately 17 per cent of patients with bipolar I disorder and 24 per cent of those with bipolar II disorder attempt suicide during the course of their illness. 

The clinical problem 

Bipolar disorder is a cyclical mood disorder that involves episodes of disruption to mood and behaviour, interspersed with periods of recovery. These disruptive episodes can either be depressive or manic (either mania or hypomania).

The Diagnostic and Statistical Manual of Mental Disorders (DSM-V) defines bipolar disorder as: 

• Bipolar I disorder: at least one manic episode is experienced
• Bipolar II disorder: at least one major depressive episode and at least one hypomanic episode are experienced.