Manic-depressive illness, also called bipolar disorder, is a condition in which periods of depression alternate with periods of mania or lesser degrees of excitement. Manic-depressive illness affects slightly less than 2% of the population to some degree. The illness is believed to be hereditary, although the exact genetic defect is still unknown. Manic-depressive illness is equally common in men and women and usually first encountered from the teenage years through to early thirties. Manic-depressive illness usually begins with depression and includes at least one period of mania at some time during the illness. Episodes of depression typically last 3 to 6 months. In the most severe form of the illness, called Bipolar I Disorder, depression alternates with intense mania. In the less severe form, called Bipolar II Disorder, short depressive episodes alternate with hypomania (mild mania). Symptoms of Bipolar II Disorder often change with the seasons, for example depression in the fall and winter, and brief excitement in the spring or summer.

In an even milder form of Manic-depressive illness called Cyclothymic Disorder, periods of elation and depression are less severe, typically lasting only a few days and recurring fairly often at irregular intervals. Although Cyclothymic Disorder may ultimately evolve into Manic-depressive illness, in many people it never leads to major depression or mania. Having a Cyclothymic Disorder may contribute to a person's success in business, leadership, achievement, and artistic creativity. However, it may also cause uneven work and school records, frequent change of residence, repeated romantic breakups or marital failure, or alcohol and drug abuse. In about a third of people with Cyclothymic Disorder, these symptoms can lead to a mood disorder that requires treatment.

The diagnosis of Manic-depressive illness is based on the distinctive pattern of symptoms. A doctor determines whether the person is experiencing a manic or depressive episode so that the correct treatment can be given. About one in three people with Bipolar Disorder experience manic (or hypomanic) and depressive symptoms simultaneously. This condition is known as a Mixed Bipolar State.

Most people with Bipolar Disorder have extreme cycles only once every few years. Those with rapid cycles may go through four or more episodes of mania and depression per year; those with ultra-rapid cycles have episodes shorter than a week, with distinct and dramatic moods shifts within a 24-hour period. Some people with Bipolar Disorder may have weeks, months, or even years with absolutely no extreme ups and downs at all. Manic-depressive illness recurs in nearly all cases. People who cycle rapidly are more difficult to treat.

In some cases, alternative methods may work in a complementary way to the use of conventional medications, helping them to work better or, in some cases, to lower necessary dosages. In other cases, alternative treatments may be effective on their own, allowing a reduction in existing medications or lessening mood swings to the point where patients can lead more normal and satisfying lives.

Hypomania shares symptoms and characteristics similar to the mania aspect of manic depression, but to a less severe degree. The characteristics of a hypomanic episode include:

• Euphoric mood lasting for at least several days on end which can switch to irritability, intolerance and rage
• Increased activity and high energy levels
• Rapid speech and flow of ideas
• Extrovert nature, seeking out people, including strangers
• Exalted self-esteem
• Loss of judgment
• Spending too much money
• Lack of inhibitions and increased sexual drive
• Increased productivity and creativity
• Feeling a need for less sleep