Bipolar Disorder

Episodes of mania and depression: types of bipolar disorder, what's known about its biology, the story of lithium, and the role of sleep and body clocks.

Highs and lows

Bipolar disorder — formerly called manic depression — is characterised by episodes of mania or hypomania and, usually, depression. During mania, people may feel euphoric or irritable, need little sleep, talk rapidly, have racing thoughts and grandiose ideas, and take serious risks with money, relationships or safety; severe mania can include psychosis. Depressive episodes resemble major depression and are often longer and more frequent than manic ones. The WHO estimated about 40 million people had bipolar disorder in 2019.

Types

Bipolar I: at least one full manic episode. Bipolar II: at least one hypomanic episode (milder, without severe impairment) and at least one major depressive episode. Cyclothymia: long-term fluctuating milder symptoms. Because people often seek help during depression, bipolar II is frequently first misdiagnosed as depression — important because antidepressants alone can sometimes trigger mania.

Biology

Bipolar disorder is among the most heritable psychiatric conditions (twin estimates around 60–85%), with many genetic variants involved, some shared with schizophrenia. Research implicates altered regulation of emotion circuits (prefrontal cortex and amygdala), dopamine and other signalling systems, cellular energy metabolism and, prominently, circadian rhythms: sleep loss can trigger mania, and many people with bipolar disorder have unstable body clocks.

The lithium story

In 1949 the Australian psychiatrist John Cade, testing ideas about toxins in urine, gave guinea pigs lithium salts and noticed they became calm. He then gave lithium to patients with mania, with dramatic results. After safety concerns delayed its adoption, lithium became a mainstay of treatment. It remains among the most effective mood stabilisers for preventing relapses and is associated with reduced suicide risk. How it works is still not fully understood. It requires blood monitoring because the effective and toxic doses are close.

Treatment and self-management

Other mood stabilisers (valproate, lamotrigine), antipsychotics and psychological therapies are used. Regular sleep and routines, learning early warning signs, and family-focused therapy help prevent episodes. Many people with bipolar disorder lead full lives, including successful careers.