Elderly men with lower levels of free testosterone in their blood appear more likely to suffer depression than those with higher amounts of the sex hormone, according to a report in the March issue of Archives of General Psychiatry.

Osvaldo P. Almeida, M.D., Ph.D., F.R.A.N.Z.C.P., of the University of Western Australia, Perth, and colleagues studied 3,987 male participants aged between 71 and 89 years old, between 2001 and 2004. The men were asked to report information about demographics and health history. They then underwent testing for depression and cognitive (thinking, learning and memory) difficulties.

Information about physical health conditions was also obtained from a short survey, and an Australian health database. The researchers also collected blood samples from the participants, and measured levels of total testosterone and free testosterone, which is not bound to proteins.

Of the almost 4,000 participants, 203 or 5.1 percent, met criteria for depression; these men had significantly lower total and free testosterone levels then men who were not depressed. After controlling for other factors — such as education level, body mass index and cognitive scores — men in the lowest quintile (20 percent) of free testosterone concentration had three times the odds of having depression, compared to men in the highest quintile.

The authors note:

The mechanism by which low hormone levels might affect depression risk has not been identified, but might involve changes in the levels of neurotransmitters or hormones in the brain.

Professor Almeida commented:

More research is needed to prove whether low testosterone causes depression or whether it’s only associated with it

Depression affects between 2 percent and 5 percent of the population at any given time, according to background information, and women are more likely to be depressed than men until they reach age 65, when sex differences almost disappear. Previously, several studies have suggested that sex hormones might be responsible for this phenomenon.

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Men’s testosterone levels are usually about 300 to 1,000 nanograms per decilitre of blood, according to the U.S. National Institutes of Health.

In a separate study, researchers in Australia found that a quarter of men aged over 60 had testosterone levels of 294 nanograms or less, per decilitre of blood.

Posted by Jonathan in Biochemistry, Psychology