Diagnosis

Bipolar disorder is more common than previously thought, but this illness, particularly bipolar disorder II, is still poorly recognized in the family-practice setting. It is estimated that only a third of affected people are accurately diagnosed.

Ruling Out Similar Conditions

When making a diagnosis of bipolar disorder, it is important that the doctor rule out other conditions that may be causing symptoms of bipolar disorder.

Distinguishing Mania from Normal Euphoria or Joy. A major difficulty with a diagnosis of bipolar disorder is the tendency for a patient to be unable to recognize his or her own condition, particularly when in the manic state. The patient often denies their symptoms, which may be perceived as positive feelings. The doctor should take a careful and complete history of any and all episodes of depression, mania, or both. Hypomania, the less severe variant of mania, may be particularly difficult to distinguish from normal joy or euphoria. It can often be distinguished by the following characteristics:

• Hypomania persists for at least 4 days
• Patients with hypomania are easily distracted and overly talkative
• Patients with hypomania have difficulty functioning

Distinguishing Unipolar from Bipolar Depression. People with bipolar disorder are more likely to seek help because of a depressive episode. Indeed, about 16% of people with bipolar disorder do not have a manic episode until they have experienced three or more depressive episodes. In such cases, the condition is often diagnosed as major depression. An accurate diagnosis is important because patients with bipolar disorder who are inappropriately medicated solely with antidepressants have a higher incidence of rehospitalization than do other bipolar disorder patients.

Bipolar disorder should be suspected in patients who have been treated for depression and who had a fast and good response, followed by the return of depression and failure to respond to other antidepressant treatment.

A family history of manic-depressive illness may make a doctor suspicious, but a diagnosis of bipolar disorder cannot be established until a manic or hypomanic episode has occurred. Patients with bipolar II disorder and those with depressive mixed state are most likely to be misdiagnosed with depression.

Attention Deficit Hyperactive Disorder (ADHD). Children or adolescents with bipolar disorder may be inappropriately diagnosed with attention-deficit hyperactivity disorder. ADHD and bipolar disorder often cause inattention and distractibility, and the two disorders may be difficult to distinguish, particularly in children. In some cases, ADHD in children or adolescents can even be a marker for an emerging bipolar disorder. The primary distinction between bipolar disorder and ADHD is the presence of a manic or hypomanic episode, which occurs in patients with bipolar disorder but not those with ADHD.

Schizophrenia. Severe manic episodes that include delusions and hallucinations may be easily confused with schizophrenia. (African-American men are more likely to be diagnosed with schizophrenia than with bipolar disorder.) The key factors that distinguish bipolar disorder from schizophrenia include:

• The presence of one or more manic or hypomanic episodes in bipolar disorder, but not in schizophrenia
• A flat emotional expression, with no variability in the voice among people with schizophrenia
• People with bipolar disorder are typically very expressive

Substance Abuse. Up to 60% of patients with bipolar disorder abuse alcohol and drugs at some point during their illness. Both diagnosis and treatment are difficult in such cases, since substance abuse is often a method of self-treatment, and withdrawal can produce symptoms of mania or severe depression. The effects of cocaine in a heavy user can also produce abnormal mood swings that closely resemble those of bipolar disorder.

Other Causes of Mood Swings. Other conditions that can cause mood swings include:

• Thyroid disorders
• Adrenal disorders (Addison's disease or Cushing's syndrome)
• Vitamin B12 deficiency
• Neurologic disorders such as Huntington's disease, epilepsy, brain tumors, encephalitis, or multiple sclerosis
• Medications, including corticosteroids and certain drugs used to treat anxiety and Parkinson's disease

Laboratory Tests

Patients should be tested for drugs or alcohol if the doctor suspects that they have been using these substances. Blood tests for thyroid function should also be performed.

Imaging Tests

Noninvasive imaging tests of the brain using magnetic resonance imaging (MRI) and positron-emission tomographic (PET) scans are being used in clinical trials for detecting abnormalities in the brain. The results of these tests may eventually help identify bipolar disorder and test the effectiveness of various treatments.