Diagnosis

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.