New research has found that there are a number of differences between the brains of men and women, both in terms of size and of composition.

Amber Ruigrok, lead researcher, along with John Suckling and Simon Baron-Cohen, professors from Cambridge’s Department of Psychiatry, collated data from 126 studies, encompassing many thousands of brains.

One notable finding was that although men on average have a larger brain volume than women, by a margin of up to 13 per cent, they do not tend to perform better than women in intelligence tests.

“It is important to note that we only investigated sex differences in brain structure,” said Ruigrok, a PhD candidate. “Integrating across different levels will be an important goal for future research.”

The analysis also found that men tend to have a larger and denser hippocampus, the part of the brain that is damaged in people who suffer from depression. Studies have shown that while women are twice as likely to be diagnosed with the illness than men, prevalence is in fact equally likely between the sexes.

The overlap between sex and brain differences “known to be implicated in psychiatric conditions”, can no longer be ignored, Ruigrok tells me. Future research should “test whether sex differences in brain structure underlie skewed sex ratios of neurological and psychiatric conditions.

“It is very important to examine males and females independently to investigate if the same brain areas are implicated in the same psychiatric conditions for each sex, or if this differs dependent on sex.”

In other words, although there is a correlation in this study between differences in the size of brain regions and specific neurological and psychiatric conditions associated with those conditions, this evidence is not sufficient to draw any kind of conclusion.

However, it does provide a useful signpost for future research, potentially through investigating sex-specific developmental processes in the brain and whether these differences are related to skewed sex ratios of mental health problems.

It has already been shown that the manifestation of autism in high-functioning adults is sex-dependent; with men tending to display more autisic characteristics than women. It is highly possible that other neuro-psychological conditions have sex dependent pathologies, with different changes occurring in the male and female brain.

If so, it may be that future treatments are tailored to an individual’s sex to allow for these differences. For this to happen neuroscience researchers will have to be more mindful than ever before of the sex and gender of their research subjects.

Professor Baron-Cohen, a renowned autism expert and author of the controversial book The Essential Difference, said: “Although these very clear sex differences in brain structure may reflect an environmental or social factor, from other studies we know that biological influences are also important, including prenatal sex steroid hormones (such as foetal testosterone) as well as sex chromosome effects.

“Such influences need to be teased out, one by one.”