We all experience a variety of moods such as happiness, sadness, and anger. Unpleasant moods and changes in mood are normal reactions in everyday life, and we can often identify the events that caused our mood to change. However, when we experience extreme mood changes that affect how we behave and function, these changes are often the result of a mood disorder.

Bipolar disorder (formerly known as manic-depressive disorder) is a mood disorder that consists of periods of extremely elevated mood (mania), extremely low mood (depression), and normal mood.

Bipolar disorder typically begins for people during adolescence and early adulthood. The most common onset is from the teenage years to the early 30s. It is unusual for bipolar disorder to begin in childhood without strong familial risk factors, and it is rare for its onset to occur after the age of 60 (unless it is associated with another medical condition). Bipolar disorder occurs in about 1% to 3% of the adult population, and men and women are affected equally. The rate of suicide for people with bipolar disorder is around 15 times higher than that of the general population.

There is no single, proven cause of bipolar disorder, but research suggests that it is the result of abnormalities in the way some nerve cells in the brain function or communicate. Researchers also believe that there is a definite genetic link (family history) in which there is a higher risk for people who have a parent or full sibling (i.e., a first-degree relative) with bipolar disorder.

Whatever the precise nature of the cause of bipolar disorder, it clearly makes people with the disorder more vulnerable to emotional and physical stresses. As a result, upsetting life experiences, alcohol, illicit drug use, lack of sleep, certain antidepressants, or other stresses can trigger episodes of illness, even though these stresses do not actually cause the disorder.

Bipolar disorder is not the fault of the person suffering from it and is not the result of a "weak" or unstable personality. Rather, bipolar disorder is a treatable medical condition.

Bipolar disorder is a condition in which the person's mood changes in cycles – from extremely high or irritable to extremely low and hopeless – over weeks to months. The nature of these mood changes varies from one person to the next. A person may go through periods of elevated mood, depressed mood, and times when mood is normal. The period of time that the extreme high and low moods are experienced are called episodes of mania and depression. It is less common for a person to alternate between mania and depression; in most, one or the other is predominant.

Mania: During a manic episode, a person will experience a high, irritable, angry, or aggressive mood for at least one week that is not caused by drug abuse, medication, or other medical conditions. The person's mood disturbance will be severe enough to cause concerns from family or friends, and may warrant a hospital stay to prevent harm to self or other. In addition, they will experience 3 or more of the following:

• needing little sleep
• being more talkative than usual, often more loudly or quickly
• having racing thoughts (thoughts that won't quiet)
• being much more active than usual
• being distracted, often by unimportant or irrelevant stimuli
• having an inflated feeling of power, greatness, or importance (inflated self-esteem)
• doing reckless things without concern about possible consequences (e.g., spending too much money, engaging in inappropriate sexual activity, or making risky business investments)

A manic episode may also include psychotic symptoms such as delusions (firmly believing things that are not true) or hallucinations (hearing, feeling, or seeing things that are not there). A person going through a manic episode is unlikely to be able to keep up with important daily obligations, such as their job or schoolwork.

Hypomania is a milder form of mania that has the same symptoms but less severe, and has less negative impact on a person's daily activities. Symptoms must last for at least 4 consecutive days. During a hypomanic episode, the person may have an elevated mood and be more productive, but the mood is uncharacteristic of the person's baseline personality. Because these episodes often feel good, the quest for hypomania may even cause some people with bipolar disorder to stop taking their medications. However, a hypomanic episode does not usually last for long and gradually shifts into either mania or depression. Therefore, it is important for hypomania to be treated.

Depression: During a depressive episode, the person experiences feelings of sadness or loses interest in the things they normally enjoy. At least 5 of the following additional symptoms persist for at least 2 weeks and cause clinically significant impairment of social or occupational functioning:

• insomnia (trouble sleeping) or sleeping too much
• depressed mood
• weight loss or weight gain (more than 5% of body weight)
• decreased interest in pleasurable activities
• fatigue or decreased energy
• problems concentrating or making decisions
• feeling slowed down or feeling too agitated to sit still
• feeling worthless or guilty or having very low self-esteem
• recurrent thoughts of death or of committing suicide

A depressive episode may also include symptoms such as severe anxiety, excessive worry, and other physical symptoms (e.g., pain) as well as psychotic symptoms such as delusions (firmly believing things that are not true) or hallucinations (hearing, feeling, or seeing things that are not there).

Some people with bipolar disorder experience mixed episodes. These are episodes of mania or hypomania which also have 3 or more symptoms of depression together or alternating frequently during the day. Individuals are excitable or agitated as in mania, but they also feel irritable and depressed. Mixed episodes present the highest risk of suicide. Approximately 25% to 50% of all people with bipolar disorder have a lifetime risk of attempting suicide.

Some people with bipolar disorder also experience problems with movement, called catatonic symptoms. These symptoms include physical agitation, immobility, and unusual movements or body positions.

Patterns of bipolar disorder

People with bipolar disorder vary in the types and frequency of episodes that they experience. Some people may have equal numbers of manic and depressive episodes, while others may have mostly one type (usually depression).

While several years can pass between the first few episodes without treatment, most people eventually have more frequent episodes. Episodes can last for days, weeks, months, or sometimes even years. For some people, the episodes have rapid cycling where they experience at least 4 episodes per year in any combination of mania, hypomania, mixed, or depression.

Classifications

According to the episode patterns, bipolar disorder can be classified as:

• Bipolar-I disorder: A person has at least one manic episode or mixed episodes and a depressive episode.
• Bipolar-II disorder: A person has only hypomanic and depressive episodes, not full mania or mixed episodes. Hypomania often seems normal to the person, and they seek treatment only for depression.
• Bipolar disorder not otherwise specified: A person has met most of the criteria for bipolar disorder but not all (e.g., shorter duration of a given episode or only hypomanic episodes).
• Cyclothymic disorder: A person has recurring hypomanic episodes and depressive symptoms.

A doctor will diagnose bipolar disorder based on a pattern of symptoms. Diagnosis usually involves a thorough medical history, questions about family history, a physical exam, and a psychiatric evaluation that assesses the individual's history of depression and manic episodes. The doctor will make sure the symptoms are not due to certain medical conditions, or due to medications or other substances. Early and proper diagnosis is an important step towards preventing other complications such as suicide, alcohol or substance abuse, marital or work problems, and more frequent cycling episodes.