July 5, 2006 — Mild sadness may trigger relapse into major depression, a Canadian study shows.

But this is more likely to happen in patients treated with antidepressants than in those who receive a form of psychotherapy called cognitive-behavioral therapy, or CBT.

Relapse is a risk for people who have recovered from major depression. One reason for relapse is that a person may still have thought patterns that can trigger a downward spiral of depressive thinking, suggest University of Toronto researcher Zindel V. Segal, PhD, and colleagues.

A tip-off to whether formerly depressed people have these risky thought patterns is how mild sadness affects their thinking. So Segal’s team studied 99 people who had recovered from an episode of major depression. Forty of them recovered after treatment with antidepressants (either Zoloft, Paxil, or Effexor); 59 recovered after CBT.

The researchers gave the recovered patients a test that measured their dysfunctional attitudes. Then they had them listen to sad music — 10 minutes of Prokofiev’s “Russia Under the Mongolian Yoke” re-mastered at half speed — while remembering a time in their lives when they felt sad.

Those whose thinking became most dysfunctional during this exercise were also most likely to relapse over the next 18 months. This “cognitive reactivity” was a stronger predictor of depression relapse than the strongest previously known predictor (the number of prior relapses).

Mild sadness was more likely to trigger dysfunctional thinking in antidepressant-treated patients than in those who recovered from depression after CBT.

The finding points to new ways to prevent depression relapse, Segal and colleagues suggest. The idea would be to teach patients to recognize — and change — dysfunctional thoughts that arise when they’re sad or stressed.

“Effective relapse prevention might be achieved through approaches that … uncouple the mood-dependent accessibility of these beliefs and attitudes …,” they write.

Segal and colleagues report their findings in the July issue of the Archives of General Psychiatry.