Risk Factors

Between 1,000,000 and 2,000,000 Americans are thought to suffer from bipolar disorder. Estimates of the lifetime risk for the disorder run between 1.0 - 1.5%. There is some indication that the incidence of bipolar disorder may be increasing, but more research is needed to confirm this.

Gender

Bipolar disorder affects both sexes equally, but there is a higher incidence of rapid cycling, mixed states, and cyclothymia in women. Early-onset bipolar disorder tends to occur more frequently in men and it is associated with a more severe condition. Men with bipolar disorder also tend to have higher rates of substance abuse (drugs, alcohol) than women.

Age

Bipolar disorder is the most common psychotic disorder, and experts believe that it occurs in 1% of people among all age groups.

Early-Onset Bipolar Disorder. In one survey, 59% of bipolar disorder patients had their first symptoms when they were children or adolescents. Typically, there was a very long delay until the condition was diagnosed and treated. Bipolar symptoms in young people closely mimic those in adulthood, but may have slight differences:

  • The initial episodes are more likely to be depressive. A study reported that 33% of children who experienced major depression developed bipolar I by age 21 and 15% of them had bipolar II disorder.
  • Manic phases usually begin in adolescence or young adulthood, with an average age of onset being 18 years. Mood often involves irritability, but in general symptoms, resemble those seen in adults (euphoria and grandiosity, flight of ideas, racing thoughts, and a decreased need for sleep).

Early-onset bipolar disease is also associated with the following characteristics:

  • A family history of bipolar disorder is usually present. Children with bipolar disorder who have one or more parents with the same disorder often have a more severe form than does the affected parent.
  • A higher rate of co-existing conditions such as panic disorder, conduct disorder, substance abuse, suicidal behavior, and psychotic symptoms may occur during bipolar episodes. Young patients are at higher risk for these complications regardless of the presence or absence of supportive parents.
  • The condition is often more severe in children than in adult patients, with a higher risk for mixed mania (simultaneous depression and mania), multiple and frequent cycles, and a long duration of illness without well periods.

Adult-Onset Bipolar Disorder. Bipolar disorder can also appear for the first time in people over the age of forty. In fact, age 40 is another peak of onset for women.

Onset Late in Life. Bipolar disorder that occurs late in life often either follows many years of repeated episodes of unipolar depression or it accompanies medical and neurological problems (particularly cerebrovascular disease, such as stroke). It is less likely to be associated with a family history of the disorder than earlier-onset bipolar disorder.

Accompanying Neurologic or Emotional Disorders

Patients with bipolar disorder, especially type II or cyclothymic disorder, have frequent episodes of major depression. Anxiety disorders also commonly coexist in these patients. For example, the occurrence of panic disorder in patients with bipolar disorder is 26 times that of the general population. Patients with bipolar disorder, particularly those with type II, are also subject to phobias. In one study, the presence of anxiety disorders was also associated with longer and more severe bipolar depressive episodes and with a higher risk for suicide.

Symptoms of bipolar disorder in children are often confused with attention-deficit hyperactivity disorder (ADHD). Furthermore, the two conditions can coincide. In one study, 65% of adolescents with bipolar disorder met criteria for ADHD. Yet another study indicated that close to 25% of children diagnosed with ADHD either already had bipolar disorder or go on to develop it. The risk for both diagnoses is highest in white males. Symptoms are also more severe in people with both conditions. Some experts believe that many of these disorders may actually be variations of a single disease.

Family History

Bipolar disorder frequently occurs within families, although genetic factors account for only about 60% of cases. Family members of patients with bipolar disorder also have a higher than average incidence of other psychiatric problems. They include schizophrenia, schizoaffective disorder, anxiety disorders, ADHD, and major depression.

Review Date: 12/13/2005
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital