Here, we will explore the topic in more detail. For centuries, doctors have recognized women’s vulnerability to depression and proposed a variety of explanations. At the beginning of the century, the female of the species, with her ‘excitable nervous system,’ was thought to wilt under the strain of menstruation and childbirth, or later, the pressures of work and family. But researchers are now constructing more scientific theories to explain why women are nearly twice as likely as men to become depressed.
Experts say that social bias and women’s higher rates of physical and sexual abuse and poverty play a role in this. But scientists are also studying genes that may predispose girls and women to the disorder. They are examining the likely role of estrogen and even linking the development of clinical depression to negative thinking, which is more common in women than in men.
There is no question that women bear the brunt of de-pression. The National Co-morbidity Study, a large survey of adults in the US released in 2003, found that almost two women for every man had experienced at least one episode of depression. Roughly the same ratio has been found in recent studies in nine other countries including Canada, Brazil, Germany and Japan.
It is unlikely that any single gene, hormone level or type of experience explains the higher incidence of depression in women. Instead, several genes probably work in concert with the ebb and flow of reproductive hormones to change brain chemistry in ways that might set the stage for depression, especially after an emotional ordeal. Another risk factor appears to be something that researchers call ‘over-thinking’, a tendency to dwell on petty slights, to mentally replay testy encounters and to wallow in sad feelings. Studies show that this type of negative thinking is far more common in women than in men, and that it can be a harbinger of clinical depression.
Experts feel that the gender difference in over-thinking is strongly tied to the gender difference in depression.
About half the risk of depression is thought to be genetic. The single gene, 5-HTT, that has been definitively linked to depression is no more common in women than in men. But preliminary research suggests that there are other depression-related genes that mainly affect women. For example, after scanning the genomes of people with major depression in families, scientists have identified 19 regions of chromosomes that were especially common and, therefore, likely to contain genes that promote depression.
Four of these regions showed up only in women and one in men. Such findings suggest that more genes may help to set off depression in women than in men, explaining in part why more women become depressed. One may be CREB1, a gene that has recently been identified as a strong candidate. Especially intriguing, is the fact that CREB 1 interacts with estrogen receptors.
Though the details of the relationship between CREB 1 and estrogen are unknown, researchers have long thought that levels of sex hormones play some role in depression. For one thing, sex difference in depression is most pronounced in women during their reproductive years, when sex hormone levels are highest. Before puberty, boys and girls have roughly equal rates of depression. The incidence of depression climbs in both sexes during puberty, but the climb is steepest for girls.
In a national telephone survey in the US of 12 to 17 year-olds, about 14 per cent of girls and 7 per cent of boys met the criteria for major depression. In their repro-ductive years, women are also especially prone to bouts of depression when their sex hormones are in flux—just before menstruation and just after childbirth. Two sub-types of de-pression that affect only women—premenstrual disorder and postpartum depression—occur at these times.
A leading theory is that sex hormones help induce de-pression in some women by affecting neurotransmitters in the brain that influence mood. The sensitivity of these neu-rotransmitters may increase when hormone levels are high or in a state of flux and decrease when they are low and stable. However, to blame women’s higher rate of depression on hor-mones is too simplistic, say experts. Not all women become depressed when their hormone levels seesaw.
A study sponsored by the National Institute of Mental Health in the US showed that manipulating women’s levels of estrogen and progesterone affected the moods of some women but not others. Specifically, women who usually suffered from premenstrual syndrome, a condition characterized by moodiness in the week or so before menstruation that is less severe than premenstrual disorder, found that their moods lifted when they were given a drug that kept their hormone levels low.
When their hormone levels went back to normal, these women felt blue. But women who did not suffer from premenstrual syndrome did not experience ups and downs in mood during the study. Such findings indicate that it is not hormone levels per se that make some women feel moody or depressed at times of hormonal flux, but an underlying vulnerability. The big question is ‘What is that vulnerability?’
Current research indicates that genes may tell much of this story. Some genes that raise women’s risk of depression may exert their effect in the presence of high levels of estrogen, their influence then decreasing when estrogen falls after menopause. But biology cannot entirely explain the sex difference.
Another important factor is the greater tendency of girls and women to ruminate over the common problems of life like criticism at work or school or rejection by a friend. In several studies over the last decade, scientists have found that women react more strongly than men to such experiences, mulling over them without being able to come to a resolution or to simply move on.
Dwelling on problems causes the initial sadness to snowball. In contrast, men are more likely to distract themselves from a problem, often by doing some physical activity, and this helps to blunt the emotional sting of everyday disappointments and setbacks. Some studies have found that people who habitually ruminate but are not depressed are more likely than non-ruminators to develop depression later.
There may be biological reasons behind women’s tendency to brood, but no genetic predisposition or difference in the brain has been found. In all likelihood, there are cultural and personality contributors to rumination. Women tend to forge intense emotional connections and to care deeply about relationships. Such an investment in relationships can be a source of great richness in women’s lives, but taken too far, it can also become destructive. A few studies have found that sex difference in negative thinking is apparent in children as young as nine, several years earlier than the sex difference in depression emerges.
Several strategies can be employed—staying active can help. For teenage girls, playing a sport or engaging in other extra-curricular activities can keep them from brooding about bad marks in exams or broken romances. If their self-esteem hinges on one thing, like a single relationship, there is no fallback if something goes wrong. Another strategy is to cultivate a circle of friends. When women ruminate, they tend to blow things up. It helps to have friends who can help you reflect on a problem and find a solution. On a lighter note, it is important to make sure that the friends are not too prone to rumination themselves.