Bipolar affective disorder

In the most commonly used classification system of mood disorders, depression and mania are viewed as representing polar extremes, as illustrated in Figure 1. ‘Bipolar’ disorders are those in which both extremes of depression and elation occur, usually in separate depressive and manic episodes, but sometimes together in what are known as mixed affective episodes. Bipolar affective disorder, previously known as manic depression, is diagnosed when a person has had two or more episodes of mood disorder in total and at least one of these has been a manic or mixed affective episode. Any of the acute affective episodes shown in Table 1 can occur during the course of the condition and, at different times in their lives, some people with bipolar disorder will experience most, if not all, of these different mood states.

Fig. 1 Classification of mood disorders.

Table 1 ICD10 classification of mood disorders

In some cases of bipolar disorder, only manic episodes occur. It might be expected that this presentation would be classified as ‘unipolar’ mania, but in fact a diagnosis of bipolar disorder is made even when there have been episodes of mania with no episodes of depression. The reason for this is the finding in cohort studies that most people with a history of manic episodes will eventually have a depressive episode. Also, people with bipolar disorder, including those who have had only manic episodes, have an increased rate of relatives with both bipolar and unipolar mood disorders. People with a history of depressive but not manic episodes tend to have a family history of unipolar depression only.

Manic episodes are divided into two types, hypomania and mania. Hypomania is milder and is only diagnosed if the person affected is able to maintain a reasonable level of social and occupational function. Mania involves a complete disruption of the person’s usual activities and when diagnosed should be classified as occurring either with or without psychotic symptoms. People with bipolar disorder who have had at least one episode of mania are said to have bipolar I disorder. Those with a history of depressive and hypomanic episodes are classified as bipolar II. A final term used in the classification of bipolar disorder is ‘rapid cycling’, which denotes a phase of illness in which there is frequent switching of mood states, defined as four or more episodes of mania and depression occurring within a period of one year.