The secret source of humour itself is not joy, but sorrow

Testa di Medusa, Caravaggio, 1593

Latin -th[ymacr]mia, from Greek -thūmiā, from thūmos, mind, soul

A persistent instability of mood, involving numerous periods of mild depression and mild elation. This instability usually develops early in adult life and pursues a chronic course, although at times the mood may be normal and stable for months at a time. The mood swings are usually perceived by the individual as being unrelated to life events. The diagnosis is difficult to establish without a prolonged period of observation or an unusually good account of the individual's past behaviour. Because the mood swings are relatively mild and the periods of mood elevation may be enjoyable, cyclothymia frequently fails to come to medical attention. In some cases this may be because the mood change, although present, is less prominent than cyclical changes in activity, self-confidence, sociability, or appetitive behaviour. If required, age of onset may be specified as early (in late teenage or the twenties) or late.

The essential feature is a persistent instability of mood, involving numerous periods of mild depression and mild elation, none of which has been sufficiently severe or prolonged to fulfil the criteria for bipolar affective disorder or recurrent depressive disorder. This implies that individual episodes of mood swings do not fulfil the criteria for any of the categories described under manic episode or depressive episode. Includes, affective personality disorder, cycloid personality, cyclothymic personality .

This disorder is common in the relatives of patients with bipolar affective disorder and some individuals with cyclothymia eventually develop bipolar affective disorder themselves. It may persist throughout adult life, cease temporarily or permanently, or develop into more severe mood swings meeting the criteria for bipolar affective disorder or recurrent depressive disorder.