Bipolar disorder is an illness, a medical condition. It most often starts with depression. People with bipolar disorder typically experience recurrent episodes of mood swings, or severe changes in mood and behaviour. Bipolar disorder is characterised by these mood changes from an elevated and irritable mood, mania or "highs", to a sad and hopeless or depressed mood or "lows". Some people may have high and low episodes or mood changes over a matter of days, some may have periods of normal mood in between. The frequency of these mood swings and the duration varies from person to person. Over time the interval between episodes often decreases. The manic episodes typically have a rapid onset. Some people may only experience the manic symptoms.

How common is it?

It is much less common than a depressive illness. One to two percent of the population will develop bipolar disorder at some point in their lives. It can start at any time during or after the teenage years, and can affect children and the elderly. Unlike some forms of depression it affects as many men as women. It is often not recognised as a serious disorder and people may have symptoms needlessly for years.

What causes it?

The causes of bipolar disorder are not fully understood. It is probably caused by a combination of factors.

Genetic factors - research has shown that bipolar disorder does seem to run in families. People with a close relative with bipolar disorder have a greater risk of developing the disorder than the general population.

Biochemical factors - mania like depression is believed to be associated with a chemical imbalance in the brain which can be corrected with appropriate medication. Current evidence suggests that there are unusually high levels of norepinephrine, one of the neurotransmitters in a person's brain, during a manic episode and low levels during a depressive episode.

Environmental factors - stress may play a part, particularly when increased in a person's life, and there are inadequate coping mechanisms to deal with it. Stress may then trigger an episode or contribute to the disorder's occurrence.

Lack of support or a physical illness may contribute to an episode.

Symptoms can also be caused by a wide range of medical and neurological conditions and substances, such as alcohol, marijuana and non-prescribed drugs. Antidepressant medication can occasionally cause a manic episode, and some medications particularly for high blood pressure can trigger depression.

What it is not?

It is not your fault, it is not a character disorder. Neither depression nor mania are a sign of weakness, nor that someone has just given in. The person is unable to just pull themselves out of it.