Do women really suffer more anxiety and depression than men? Or do doctors ask the sexes different questions while brain research provides misleading results?
Is he feeling her pain?
Larry Summers ultimately resigned from the presidency at Harvard University because he suggested that there were differences in the way male and female minds approach the study of science. While the jury is still out on Summers's controversial statements, researchers have begun to discover in their studies in mice that males and females do have a fundamentally different experience, at least, when it comes to anxiety.
The findings of Australian scientists who recently analysed how male and female mice are prone to stress ran counter to expectations. The researchers, led by Dr Tim Karl from the Garvan Institute of Medical Research in Sydney, looked at the effects on anxiety in mice of a neurotransmitter called neuropeptide Y (NPY). NPY, which is found in the brain, is thought to lower anxiety levels, and so it was no surprise that mice genetically engineered to not have the gene for NPY were more anxious.
More curious, however, was the finding that male mice without NPY were more anxious than females without it, a counter-intuitive result because in humans it is women who tend to be diagnosed more often with anxiety disorders. Since males do not exhibit the fluctuations linked to the oestrogen cycle of females, male mice have been used in more than four-fifths of the studies of the anxiety-regulating neurotransmitter, NPY.
Moreover, the large difference in results between males and females suggests something that reaches far beyond this specific neurotransmitter in mice: gender differentiation is frequently absent in scientists' study of the brain. The study suggests that only through separate examination of the chemistry in the brains of both genders will researchers gain maximum understanding of whatever phenomenon is under analysis.
Just as males are more commonly used in laboratory tests on mice, so clinical trials of people in the past have more commonly looked at men. Organisations such as the Society for Women's Health Resources in the United States have worked to remove these biases. The group has argued that men's and women's bodies can react differently to drugs and treatment, whether for mental or physical conditions, and show far different symptoms and patterns of disease.
But nowhere are these differences more apparent than with depression and related anxiety disorders. Until they are aged about 13, the sexes display equal susceptibility to these afflictions, but later females suffer more commonly and women are diagnosed with depression at about twice the rate as men. However, there is some evidence that men might suffer from depression and other psychiatric disorders more often than commonly thought. Dr Peter Branney, a research fellow at the Centre for Men's Health at Leeds Metropolitan University in England, says the difference in how commonly the sexes are diagnosed with mood disorders may not reflect how often they actually suffer from them.
"Maybe general practitioners and mental health professionals aren't good at detecting mood disorders in men, or they have a bias in detecting them in women," he says. "The bias towards women might be that [clinicians] may be more likely to talk to women about their emotions, and depression is about mood and emotion. "With men, they might be more likely to talk about practical things. Rather than how are you feeling, it's a case of what have you been doing."
Take not being able to sleep, a common symptom of depression. Dr Branney says health professionals might tend to ask a female patient how this problem affected their mood. With a male patient, by contrast, the questions will more commonly relate to practical issues such as what the patient has been doing to try to combat their insomnia. Also, depression in men is sometimes associated with aggressive behaviour, but this is not used in the diagnostic classification of depression, again making it more likely that in men the condition may not be recognised.
"It may be that we see a bias towards focusing on women's emotions and seeing women as people who are emotional, while some people may say that men are not as good at talking about their emotions," says Dr Branney. Among clinicians, Dr Branney says, there is recognition of the "stereotypical" differences between men and women, but not enough awareness of how the sexes may differ in how they present and deal with psychological problems.
Just as more women than men are diagnosed with depression, so borderline personality disorder (BDP) is more often seen in females. In fact, between two-thirds and three-quarters of those diagnosed are female. BPD is a condition characterised by among other things unusually large mood swings and problems in forming stable relationships. Dr Shirley Yen, an assistant professor of research in the department of psychiatry and human behaviour at Brown University, Rhode Island, United States, says there are reasons to believe that, as could be the case with depression, men may more commonly go undiagnosed.
"BPD tends to be more diagnosed in women than men, and I think that's something people have argued is a bias," she says. One of the potential reasons for this, Dr Yen believes, is that, also as with depression, there are differences in the traits or personal histories that accompany the condition. For example, women with BPD are more likely than men with the disorder to have been the victims of childhood abuse or to have suffered from eating disorders. Men with BPD, on the other hand, more commonly are involved with substance abuse of some kind. This substance abuse may be more readily identified than the BPD, which is then masked and as a consequence not diagnosed.
In another example, both men and women with BPD are more prone than the average to impulsive behaviours. With men, however, this trait manifests itself as a tendency to get into fights or other criminal behaviour, which more readily leads to a diagnosis of antisocial personality disorder rather than BPD. As a result of these clinical differences, Dr Yen says it is unclear whether women are actually more prone to BPD, or whether they make up the majority of diagnoses because the condition is more readily identified in females.
"There are clinical differences in how they present and so that might be the reason why there's a disparity in men and women being diagnosed," says Dr Yen. "With men, BPD might take a back seat to some of the other behaviours that are more readily externalised. "With men, you're more likely to see some of the aggressive behaviours that might attract more clinical attention [than the BPD]." While the chemical imbalances that may lead to mental illness remain a largely uncharted frontier, further study of gender differences in the brain's functioning appear to introduce a set of useful questions.