The incidence of bipolar disorder among relatives of affected patients is higher than in the general population and highest among maternal relatives. The closer the relationship, the greater the susceptibility.

Although certain biochemical changes accompany mood swings, it’s unclear whether these changes cause the mood swings or result from them. With both mania and depression, intracellular sodium concentration increases during illness and returns to normal with recovery.

Patients with mood disorders have a defect in the way the brain handles certain neurotransmitters—chemical messengers that shuttle nerve impulses between neurons. Low levels of the chemicals dopamine and norepinephrine, for example, have been linked to depression, whereas excessively high levels of these chemicals are associated with mania.

Changes in the concentration of acetylcholine and serotonin also may play a role. Although neurobiologists have yet to prove that these chemical shifts cause bipolar disorder, it’s widely assumed that most antidepressants work by modifying these neurotransmitter systems.

New data suggest that changes in the circadian rhythms that control hormone secretion, body temperature, and appetite may contribute to the development of bipolar disorder.

Emotional or physical trauma, such as bereavement, disruption of an important relationship, or a serious accidental injury, may precede the onset of bipolar disorder; however, bipolar disorder often appears without identifiable predisposing factors.

Manic episodes may follow a stressful event, but they’re also associated with antidepressant therapy and childbirth. Major depressive episodes may be precipitated by chronic physical illness, psychoactive drug dependence, psychosocial stressors, and childbirth. Other familial influences—especially the early loss of a parent, parental depression,
incest, or abuse—may predispose a person to depressive illness.

The manic patient typically appears euphoric, expansive, or irritable with little control over his activities and responses. He may describe hyperactive or excessive behavior, including elaborate plans for numerous social events, efforts to renew old acquaintances by telephoning friends at all hours of the night, buying sprees, or promiscuous sexual activity. He seldom hesitates to start projects for which he has little aptitude.

The patient’s activities may have a bizarre quality, such as dressing in colorful or strange garments, wearing excessive makeup, or giving advice to passing strangers. He often expresses an inflated sense of self-esteem, ranging from uncritical self-confidence to marked grandiosity, which may be delusional. Common features of the manic phase are accelerated speech, frequent changes of topic, and flight of ideas. The patient is easily distracted and responds rapidly to external stimuli, such as background noise or a ringing telephone.

Physical examination of the manic patient may reveal signs of malnutrition and poor personal hygiene. He may report sleeping and eating less than usual.

Hypomania can be recognized during the assessment interview by three classic symptoms: elated but unstable mood, pressured speech, and increased motor activity. The hypomanic patient may appear elated, hyperactive, easily distracted, talkative, irritable, impatient, impulsive, and full of energy but seldom exhibits flight of ideas, delusions, or an absence of discretion and self-control.

The patient who experiences a depressive episode may report a loss of self-esteem, overwhelming inertia, social withdrawal, and feelings of hopelessness, apathy, or self-reproach. He may believe that he’s wicked and deserves to be punished. His growing sadness, guilt, negativity, and fatigue place extraordinary burdens on his family.

During the assessment interview, the depressed patient may speak and respond slowly. He may complain of difficulty concentrating or thinking clearly but usually isn’t obviously disoriented or intellectually impaired.