Sleep problems. Patients with bipolar depression have an increased need for sleep (the opposite of what they experience during highs), are sleepy during the day regardless of how many hours they sleep, and have difficulty getting up in the morning. Patients with unipolar depression also have a sleep disturbance: they may fall asleep easily, sleep for a few hours, and then awaken but are unable to fall back to sleep.31 Yet these patients usually do not complain of sleepiness during the day.
Diurnal variation of mood. Patients with unipolar depression often report that their depressive symptoms fluctuate in a circadian manner. For example, they may report that their depression is worse in the morning but improves toward evening.31 This regular alteration of circadian rhythm usually is not evident in patients with bipolar depression, whose mood may vary unpredictably or in response to stressors. Some patients with bipolar disorder, however, exhibit ultradian (ultra-rapid) mood cycling, which may be confused with the diurnal mood variation seen in patients with unipolar depression.
Tendency to recur. Although both unipolar and bipolar depressive episodes recur, a pattern of multiple recurring episodes beginning in early life is characteristic of bipolar spectrum disorders.
Behavioral history. Patients with bipolar depression are more likely than patients with unipolar depression to have a history of multiple marriages, multiple romantic relationships, episodes of promiscuity, legal problems, or financial extravagance.
Response to antidepressants. Patients with bipolar depression exhibit atypical responses to antidepressant monotherapy, such as worsening of depressive symptoms, initial improvement of mood with subsequent loss of effectiveness, premature response to an antidepressant (eg, improvement of mood within 1 to 2 days of beginning the antidepressant), fluctuation of depressive symptoms (mood cycling), or precipitation of a hypomanic or manic episode. We believe that a history of multiple failed antidepressant trials is compelling evidence of misdiagnosis of a bipolar spectrum disorder as unipolar depression.
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