Depression most often does not arise out of nothing. Most people who experience clinical depression have a history of trauma, loss or a family history of depression. Trauma, be it from bereavement, abuse, accident or environmental catastrophe release a flood of Cortisol into the brain. Cortisol is a necessary chemical in the human brain but too much of it tends to reset neural activity into a maladaptive alarm and stress state.

Being in a stress state for a number of months and years takes a terrible toll on the body and mind. When people have lived like this for years they tend to be quite prone to depression. At other times in their lives, when a stresser comes along, they may cope with stress by becoming depressed.

Anyone with a significant family history of depression is at risk themselves for the condition. The genetics of depression are not entirely understood just yet but it is clear that if a blood relative has been treated for clinical depression you are at greater risk for developing the condition.