Figures for the lifetime prevalence of depression vary according to the criteria used to define depression. Using DSM-IV's criteria for 'major depressive disorder' which are similar to the ICD-10 criteria for 'moderate depression', the lifetime prevalence of depression is about 15 percent and the point prevalence about 5 percent. This means that an average person has about a one in seven (15 percent) chance of developing depression in the course of his or her lifetime, and about a 1 in 20 (5 percent) chance of suffering from it at this very point in time.
However, these figures mask a very uneven gender distribution as depression is about twice as common in women than in men. The reasons for this uneven gender distribution are not entirely clear, but are thought to be partly biological, partly psychological, and partly sociocultural.
1. Compared to men, women may have a stronger genetic predisposition to developing depression.
2. Compared to men, women are much more subjected to fluctuating hormone levels. This is especially the case around the time of childbirth and at the menopause, both of which are associated with an increased risk of developing depression.
3. Women are more ruminative than men, that is, they tend to think about things more—which, though a very good thing, may also predispose them to developing depression. In contrast, men are more likely to react to difficult times with stoicicism, anger, or substance misuse.
4. Women are generally more invested in relationships than men. Relationship problems are likely to affect them more, and so they are more likely to develop depression.
5. Women come under more stress than men. Not only do they have to go work just like men, but they may also be expected to bear the brunt of maintaining a home, bringing up children, caring for older relatives, and putting up with all the sexism!
7. Women are more likely to seek out a diagnosis of depression. They are more likely to consult a physician and more likely to discuss their feelings with the physician. Conversely, physicians (whether male or female) may be more likely to make a diagnosis of depression in a woman.
Perhaps you can think of some other reasons why depression is twice as common in women than in men, in which case please do let me know!