Neither Tom nor Mary could identify any major stressor in their lives to explain the onset of their symptoms.

A recent study has shown that there may be important differences between rapid-onset depressions and those that come on more gradually. (Hegerl U et al. J Clin Psychiatry 2008;69:1075-80). This was a retrospective study of 158 patients in Germany who had either major depressive disorder (108) or bipolar disorder (50). Rapid onset of a full-blown depression occurred in 58% of those with bipolar disorder; however, only 7% of those with major depression had a rapid onset of depression. Researchers then looked at onset of a full depression within a month. They found that 92% of bipolar people had onset within four weeks. In contrast, 68% of people with major depression experienced the onset of their depression over more than a month. There was a small group of patients who had very rapid onset of their depression — in 3 days or less — that showed a much greater incidence of libido loss and suicidal ideation when compared to a group whose depression came on over more than 30 days — 42% rapid: 15% slow for suicidal ideation; and 85% rapid: 46% slow for low libido.

This is a unique study and it suggests that the onset of depression is much more rapid in bipolar patients. It may point to a marker for bipolar illness even in people with only a history of depression — this needs further confirmation. According to the authors’ speculation, the finding suggests that there may be neurobiological differences in the two groups of patients and their depressive mechanisms.

Bottom line

Rapidly evolving depression should make the clinician wonder about bipolarity. Check the family history carefully for hospitalizations or intermittently dysfunctional relatives.

To screen for bipolar history, ask your patient about prior times when he or she may have had a period of elevated mood — when they felt:

• extra good
• needed little sleep, so that they’d be raring to go after 3-4 hours a night

Bipolar people tend to be impulsive in two areas when they are hypomanic:

• money
• sex

Ask about spending large amounts of money on inappropriate things. One of my patients bought a whole new set of furniture for his already well-furnished condo. This must be distinguished from impulse buying and shopping, which is quite common; look for disregard of consequences in purchases for the bipolar; impulse shoppers are often guilt ridden.

People in a hypomanic mood may get involved in sexual liaisons and activities that they wouldn’t normally do. Ask about such incidences specifically, as there’s often a great deal of associated shame with whatever happened. You must carefully screen out episodes that happen while the person is under the influence of drugs or alcohol — people in a hypomanic mood may abuse substances, but to make a clear diagnosis, some of this behaviour must occur while they are drug free.

I chose our two patients because they fit the pattern this research suggests:

MARY had a unipolar depression that was treated with psychotherapy and antidepressants

TOM was started on an antidepressant and had a hypomanic response within a few weeks. In retrospect, he might have had hypomanic behaviour in the past; he also recalled a relative who may have been bipolar. He was followed closely enough so that the mood shift was caught early and the antidepressant was stopped.