SEX DIFFERENCES IN MENTAL HEALTH: A REFLECTION
Only a little more than a month ago, on the morning of the 15th of February, I had my usual Italian breakfast in an unusual Airbnb in Turin. I left Italy two years ago to become a researcher, and now I had the chance to return to my home country to attend one of the most relevant international conferences for my area of interest: the 10th International Meeting “Steroids and Nervous System” (15th– 20th of February 2019).
The meeting was organised in a historical building where lessons of science and anatomy were held back in the 19th century. The famous doctor Cesare Lombroso, (in)famous for having attributed moral quality to physical appearance, also opened the questioned museum of psychiatry and criminology in the same edifice.
The amphitheatric room was evocative of centuries of knowledge. I was there, surrounded by the experts in the field, the air scented with ancient knowledge.
The dissonance between old times and the new scientific insights gave the meeting a charming atmosphere.
The meeting addressed the state-of-art of research on steroids — a class of hormones that regulates everything, from sugar levels to blood pressure to memory — and their role in the interplay between body and mind. Sixty-six studies were presented over five days of work.
There are different types of steroid hormones, which can bring various types of messages to and from the brain, and regulate emotions and behaviours, including our stress response. However, the hormones that I am studying, and the reason I was there, were the sex hormones and the role of sex differences in mental health.
By studying “sex differences” in mental health, I am investigating the underlying mechanisms which may causes some well-known differences between women and men.
For example, depression is more common in women than in men. Indeed, in 2008 the lifetime incidence of depression in the USA was 1 in 8 in males and 1 in 5 in females.
Moreover, sex differences could regulate the age of onset of mental disorders; for example, schizophrenia tends to show itself earlier in men than in women.
These are just a couple of examples to highlight why sex differences in mental health are such a hot topic in research.
So, what are the sex hormones, and what do they do?
Female hormones, like estrogen and progesterone, and male hormones, like testosterone, are usually considered only important for the development of our body toward the biologically-assigned features of our sexes, and for sex-specific processes such as menstruation, pregnancy or spermatogenesis.
But in reality they do much more.
One study has looked at the socio-sexual behaviour and birdsong of canaries. An increase in testosterone levels in the brain leads to a rise in song’s tone frequency and thus change the way birds communicate.
Let’s consider another example. You may think that running for 30 minutes has the same relaxing consequences in women and in men. However, one study found that, in mice, males seem to benefit from exercising with almost an anti-anxiety effect; yet, in females, exercising improves resilience to stress and increases physical arousal.
Not surprisingly, the other researchers at the conference went on and on about the importance of studying sex hormones to understand sex differences in terms of the differential vulnerability and resilience to different mental disorders that we see in males and females.
But what about timing?
Sex hormones vary during the life-span; they increase and decrease at different times of the day and at different ages. So, when exactly do these hormones start to influence our mental health?
Well, actually this is probably sooner than we think. As early as in our mum’s tummy.
Previous studies from our research group have shown that mothers who are depressed in pregnancy have increased levels of another steroid, cortisol, which is important for the stress response. More interestingly, their babies tend to respond more to stress, by producing more cortisol.
But are these effects different in male babies and female babies?
Another series of studies conducted in mothers who were stressed at the time of pregnancy show that male children would tend to show earlier consequences, in the way that they developed skills such as language and movement, while in female children, it was observed that while they appeared unaffected until preadolescence, they then began to show signs of anxiety.