There are several biological theories that try to explain depression but none stand out as definitive. Suggestions include a genetic component to depression, a form of impaired response to stress, and impaired brain structures.
But don't antidepressants work at the biological level?
Antidepressant medications certainly do alter neurotransmitter function but there is still no valid or simple theory that states depression is due to excesses or deficits of particular neurotransmitters. Antidepressants don’t work for everyone and it seems they may have little if any effect on mild to moderate depression.
So, what about 'impaired response to stress?'
The stress hormone cortisol is often found in abnormally high levels during depression and this suggests that depression may be related to some biological defect in the way we respond to stress.
Does biology make women more likely to be depressed?
That’s true and the most obvious difference between men and women, at the biological level, is hormones. Female hormones, and specifically hormonal changes, are considered by many experts to affect vulnerability to depression.
To what extent is depression a psychological issue?
There is strong evidence to link thinking styles to depression. Negative thinking in particular is a factor considered to cause and maintain depression.
But negative thinking styles must start somewhere?
Of course. Most people experience some form of negative thinking after particularly stressful or difficult life events. However, negative thinking may develop over time and some people appear to develop a mind-set that explains their experiences and views of the world in negative terms. Among other things, they may believe they have no personal power to influence change.
So depression can be caused by bad life experiences?
Negative life events can certainly trigger a depression, but it is wrong to suggest it is inevitable. The fact remains that most people who experience such events may experience a low mood, but they do not go on to develop depression.
If I reduce my stress, do I reduce my chances of getting depressed?
Over the long term you may, but this presupposes you are vulnerable to stress or depression. The relationship between stress and depression isn’t one way, with stress causing depression. Having depression is itself stressful and over time the nature of the depression and the issues that trigger it can change.
Doesn't the cause of depression seem vague?
Depression is certainly a complex knot to untangle. We know much more about the circumstances likely to trigger a depression – such as loss and interpersonal events – but we’ve also learned that personality and thinking styles matter a great deal and that’s why cognitive therapy can be so effective.
Is vulnerability to depression both biological and psychological?
Vulnerability to depression may be biological, or psychological, or both. We also need to factor in the social dimensions that include amongst other things, personal relationships, poverty and social and emotional support.