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Remember the book turned early 90s cultural phenomenon, Men are from Mars, Women are from Venus? Well, it seems the authors were on to something. Exciting research from the Centre for Addiction and Mental Health in Canada (CAMH) and the University of Pittsburgh has identified, for the first time, biological markers in the brain that can potentially explain why women are twice as likely to suffer from major depressive disorder (MDD) than men.

MDD is the global leading cause of disability. So far, many studies on MDD have tended to use mainly men as participants which, unfortunately, doesn’t help women now that we know there are potential brain differences between the sexes. We know that women are twice as likely to be depressed than men and four times as likely than men to be diagnosed with recurrent MDD. Women report different symptoms than men and that their symptoms are more severe. Studies have shown that testosterone may help protect men from depression because testosterone has an antidepressant effect.

A recent survey released by the National Center for Health Statistics found that 5.5 per cent of men experienced symptoms of depression compared to 10.4 per cent of women between 2013 and 2016 and that high-income men were the least likely to report depression. Twenty per cent of low-income women reported depression compared to 2.3 per cent of high-income men.

Previous studies have revealed that while many men with MDD also have substance abuse problems, women with MDD tend to have anxiety as a co-occurring illness. And in the type of depression called hypersomnia, which has to do with weight gain and sleep disturbances, women are three times more likely than men to suffer from it, yet there’s a lack of studies with women as participants. 

Now, however, a new study published in the Journal of Biological Psychiatry has found biological differences in the expression of genes in males and females with MDD. Researchers have found that men and women with MDD have opposite changes in the same genes. According to the study, only 21 of the same genes in men and women with MDD were changed in the same direction out of a total of 706 genes that are affected by men with MDD and 882 genes in women with MDD. Fifty-two genes expressed changes in opposite directions and that’s what has caught researchers’ attention.

"These findings confirm the absolute necessity of doing parallel studies in men and women and of reassessing what we've taken for granted – depression is not just depression," says Dr. Etienne Sibille in a press release. Dr. Sibille is the senior author of the study and Chair of the Campbell Family Mental Health Research Institute at CAMH.

Researchers examined the post-mortem brains of 24 women and 26 men with MDD for the study so a limit of the study is that researchers do not know exactly when the molecular changes occurred. Nevertheless, the study proves that there are molecular differences and because of that, new treatments can be tailored to men and women with MDD.

"This important paper highlights the divergent molecular mechanisms contributing to depression in men and women,” says Dr. John Krystal in the press release. Dr. Krystal is the Editor of Biological Psychiatry. “It challenges the assumption that a similar diagnosis across people has the same biology."

CAMH and Pittsburgh University researchers conclude that the different types of treatments offered to men and women with MDD may vary according to whether the immune system is suppressed which they suggest for men, or boosted, which they suggest may be more appropriate for women and encourage further research and studies to expand on their current findings.

REFERENCES:

Marianne L. Seney, Zhiguang Huo, Kelly Cahill, Leon French, Rachel Puralewski, Joyce Zhang,
Ryan W. Logan, George Tseng, David A. Lewis, and Etienne Sibille, (March 2018), Opposite Molecular Signatures of Depression in
Men and Women, http://www.biologicalpsychiatryjournal.com/article/S0006-3223(18)30065-9/fulltext

Cision, (March 2018), Centre for Addiction and Mental Health, Men and women have opposite genetic changes in depression, https://www.newswire.ca/news-releases/men-and-women-have-opposite-genetic-changes-in-depression-676659293.html

Beth Waitzfelder, Christine Stewart, Karen J. Coleman, Rebecca Rossom, Brian K. Ahmedani, Arne BeckJohn E. Zeber, Yihe G. Daida, Connie Trinacty, Samuel Hubley, Gregory E. Simon, (February 2018), Journal of General Internal Medicine, Treatment Initiation for New Episodes of Depression in Primary Care Settings, https://link.springer.com/article/10.1007%2Fs11606-017-4297-2/fulltext.html

Paul R. Albert, PhD, (July 2015), Journal of Psychiatry and Neuroscience, Why is depression more prevalent in women?, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4478054/