The cause of bipolar disorder is unclear, but hereditary, biological, and psychological factors may play a part. For example, 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. Children with one affected parent have a 25% chance of developing bipolar disorder; children with two affected parents, a 50% chance. The incidence of this illness in siblings is 20% to 25%; in identical twins, the incidence is 66% to 96%.

Although certain biochemical changes accompany mood swings, it isn’t clear whether these changes cause the mood swings or result from them. In 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 may also play a role. Although neurobiologists have yet to prove that these chemical shifts cause bipolar disorder, it’s widely assumed that most antidepressant medications 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 symptoms 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 commonly 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 caused 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. (See Cyclothymic disorder.)

The American Psychiatric Association estimates that 0.4% to 1.2% of adults experience bipolar disorder. This disorder affects women and men equally and is more common in higher socioeconomic groups. It can begin any time after adolescence, but onset usually occurs between ages 20 and 35; about 35% of patients experience onset between ages 35 and 60. Before the onset of overt symptoms, many patients with bipolar disorder have an energetic and outgoing personality with a history of wide mood swings.

Bipolar disorder recurs in 80% of patients; as they grow older, the episodes recur more frequently and last longer.

Signs and symptoms vary widely, depending on whether the patient is experiencing a manic or a depressive episode. The manic patient:

• typically appears grandiose, euphoric, expansive, or irritable with little control over his activities and responses

• may appear hyperactive or describe 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

• may have a bizarre quality, such as dressing in colorful or strange garments, wearing excessive makeup, or giving advice to passing strangers

• commonly expresses an inflated sense of self-esteem, ranging from uncritical self-confidence to marked grandiosity, which may be delusional

• may have accelerated and pressured speech, frequent changes of topic, and flight of ideas

• is easily distracted and responds rapidly to external stimuli, such as background noise or a ringing telephone

• may have signs of malnutrition and poor personal hygiene

• may report sleeping and eating less as well as being more physically active than usual.

Hypomania, more common than acute mania, can be recognized during the assessment interview by three classic symptoms:

• euphoric but unstable mood

• pressured speech

• increased motor activity.

The hypomanic patient:

• may appear elated, hyperactive, easily distracted

• is talkative, irritable, impatient, impulsive, and full of energy

• seldom exhibits flight of ideas. (Delusions and other symptoms of psychotic intensity are never present.)

The patient who experiences a depressive episode may speak and respond slowly but is not usually disoriented or intellectually impaired. His growing sadness, guilt, negativity, and fatigue place extraordinary burdens on his family. He may report:

• loss of self-esteem

• overwhelming inertia

• difficulty concentrating

• social withdrawal

• feelings of hopelessness, apathy, or self-reproach

• feelings of being wicked and that he deserves to be punished.

Physical examination of the patient with a depressive episode may reveal:

• reduced psychomotor activity

• lethargy

• low muscle tonus

• weight loss

• slowed gait

• constipation

• sleep disturbances (falling asleep, staying asleep, or early morning awakening)

• sexual dysfunction

• headaches, chest pains, and heaviness in the limbs.

Typically, symptoms are worse in the morning and gradually subside as the day progresses.

The patient’s concerns about his health may become hypochondriacal, such that he may worry excessively about having cancer
or some other serious illness. In an elderly patient, physical symptoms may be the only clues to depression.

• This illness is associated with a significant mortality; 20% of patients commit suicide, many just as the depression lifts.

• There are significant economic and social stresses associated with bipolar disorder. For example, families may suffer economic hardship if an individual’s mania is associated with unchecked spending.

• Studies show that the prevalence of cardiovascular disease risk factors (smoking, obesity, hypertension, dyslipidemia, and type 2 diabetes) is twice as high among individuals with bipolar disorder than in the general population.

For characteristic findings in patients with this condition, see Diagnosing bipolar disorders, page 33.

Diagnosing bipolar disorder requires a team approach in order to rule out medical, neurologic, and psychiatric problems that impact the diagnosis. In addition to physical and psychological examinations the patient may require:

• hematologic, endocrine, and other laboratory tests to rule out medical causes of mood changes, such as hypothyroidism, hyperthyroidism, uremia, or psychoactive substance abuse

• neurologic evaluation and imaging studies to rule out disturbances, such as cerebral arteriosclerosis, parkinsonism, psychoactive drug abuse, brain tumor, and uremia

• review of the medications prescribed for other disorders, which may indicate the possibility of druginduced depression or mania.

Treatment for bipolar disorder commonly consists of:

• drug therapy prescribed by a psychiatrist

• psychotherapy, which provides support and guidance

• cognitive behavioral therapy, which helps patient change negative thought patterns

• family therapy