Why do people remain vulnerable to depression?

New research shows that during any episode of depression, negative mood occurs alongside negative thinking (such as ‘I am a failure’, ‘I am inadequate, ‘I am worthless’) and bodily sensations of sluggishness and fatigue. When the episode has passed, and the mood has returned to normal, the negative thinking and fatigue tend to disappear as well. However, during the episode a connection has formed between the moods that were present at that time, and the negative thinking patterns.

This means that when negative mood happens again (for any reason) a relatively small amount of such mood can trigger or reactivate the old thinking pattern. Once again, people start to think they have failed, or are inadequate – even if it is not relevant to the current situation. People who believed they had recovered may find themselves feeling ‘back to square one’. They end up inside a rumination loop that constantly asks ‘what has gone wrong?’, ‘why is this happening to me?’, ‘where will it all end?’ Such rumination feels as if it ought to help find an answer, but it only succeeds in prolonging and deepening the mood spiral. When this happens, the old habits of negative thinking will start up again, negative thinking gets into the same rut, and a full-blown episode of depression may be the result.

The discovery that the link between negative moods and negative thoughts remains ready to be re-activated, even when people feel well, is of enormous importance. It means that sustaining recovery from such depression depends on learning how to keep mild states of depression from spiralling out of control.