As winter begins, so does the onset of a major episode of depression for some people. Experts in seasonal affective disorder (SAD) presented the latest evidence for treating patients with selective serotonin reuptake inhibitors (SSRIs) or a fluorescent light box at last month’s Canadian Psychiatric Association meeting in Victoria, British Columbia.

"We know that most depressions are caused by a disturbance in the serotonergic system, which may also be at work in SAD. This would explain the effectiveness of SSRIs and light therapy, which is thought to impact the serotonergic system," said Anthony Levitt, M.D., head of the Mood Disorders Program at Sunnybrook Health Sciences Centre in Toronto.

Levitt and Raymond Lam, M.D., co-edited the 1999 Canadian Consensus Guidelines for the Treatment of SAD. Lam is a professor and head of the division of mood disorders in the department of psychiatry at the University of British Columbia in Vancouver.

He also presented the results of several controlled studies showing that fluorescent light therapy is effective in 60 percent to 90 percent of patients diagnosed with SAD. Researchers have found that early morning exposure to bright light is more effective than evening exposure to bright light.

Because light therapy and SSRIs are both effective treatments for SAD, Levitt referred to the criteria in the consensus guidelines for choosing which treatment is best for a particular patients.

"Light therapy should be considered for patients who have less severe depression, are at greater risk for side effects with SSRIs, and prefer a natural method of treatment," said Levitt.

According to the consensus guidelines, patients should buy a fluorescent light box that has been clinically tested and approved by a regulatory body. The experts recommend a light box with 10,000 lux of white light that filters out ultraviolet light. Patients should use the light box for 30 minutes daily in the early morning for the entire winter season after an initial trial of four weeks, said Levitt.

"Because SAD is a recurring illness, we recommend that patients start light therapy one to two weeks prior to the usual onset of symptoms," said Levitt. He noted that follow-up studies of patients with SAD show that only 20 percent were in full remission about five years later, compared with 43 percent who still had SAD and 37 percent who developed nonseasonal depression.

Physicians should consider prescribing fluoxetine or sertraline if the patient has been diagnosed with severe depression, has certain preexisting eye conditions, finds light therapy inconvenient, and has insurance coverage for psychiatric medications, said Levitt. While other SSRIs may be effective as well, they have not been studied for SAD.

He noted that insurance companies rarely cover the purchase of fluorescent light boxes, which run between $200 and $300.

"The consensus guidelines recommend an eight-week trial for patients on an SSRI and then continuing it the entire winter season, if the patient responds," said Levitt. The guidelines also recommend starting the SSRI two to four weeks before SAD symptoms have appeared in the past.

Physicians should consider continuing the SSRI beyond winter if the patient shows signs of nonseasonal depression, including vegetative or mood symptoms, said Levitt.