Stressors and the environment cause depression

Professor Wayne Drevets discusses the ways in which stress can lead to depression. Research into interactions between stress and genes include a mutation in the serotonin transporter region.

The early onset form of depression has commonly been associated with stressors – stressful situations. That can include both social stressors like for example abuse, physical or sexual abuse, or it can include physiological stressors like some medical illness or perhaps the stressor of going through a pregnancy and delivering, or it can include stressful situations arising with just repetitive stress like bullying or perhaps even family stress or job stress. In this context, it is thought that there are gene-environment interactions that are playing some role. The gene-environment interaction that has been characterized best in depression so far has involved a mutation in the serotonin transporter region and the serotonin transporter ends up being the main target of most anti-depressant treatments (the main primary target of most anti-depressant treatments), so it’s had relevance for studies in depression. It turns out this particular mutation will increase the risk of depression only within the context of stress arising early in life. Now once the course of depression begins though, the role of stressors seems to become less prevalent. Later in life the new episodes often don’t have any clear stressful precipitants at all, and the episodes become more spontaneous and sometimes they don’t go away even when the stressor is resolved. So the end state of depression is often where you get spontaneous, recurrent or even chronic depression that gets harder and harder to treat and becomes more and more disabling, and where one stops going back to normal (the normal mood state between episodes). At this point we don’t know how to distinguish those individuals that will end up in that more chronic, disabling end state versus those individuals that will be somehow resilient and can get over an episode of depression and then may go years without another episode.