Men with low testosterone symptoms were almost three times as likely to be depressed as those with higher testosterone levels.
The study, which appears in the March 2008 issue of the Archives of General Psychiatry, shows that older men with abnormally low free testosterone levels are 271% more likely to display clinically significant signs of depression than men with higher testosterone levels.
Lead author Dr. Osvaldo P. Almeida, MD, Ph.D., director of research at the Western Australian Centre for Health and Ageing, and professor and chair of Geriatric Psychiatry, School of Psychiatry and Clinical Neurosciences, at the University of Western Australia, in Perth, notes that: "Older men with depression should be assessed for hypogonadism, and older hypogonadal men who fail to respond to standard antidepressant therapy may benefit from testosterone replacement."
The study looked at 3,987 men aged 71 to 89 years who live in Perth, Australia. The men were screened for cognitive impairment and depression, and 203 (5.1%) had a score within the depression range (scores of 7 or more). Compared with men in the highest 20%, the odds of having depression in men in the lowest 20% for total testosterone were almost doubled. This change could be accounted for by other health problems, but when they looked at the more reliable "free testosterone" blood test, the researchers found that even after eliminating the effects of other health issues, the low testosterone itself was associated with a 270% higher risk of depression.
According to Dr. Almeida, "The findings of this study are compelling in suggesting a causal relationship between low free testosterone and depression in older men… The association is biologically plausible; there is evidence from lab work that testosterone may increase the bioavailability of serotonin and noradrenaline in the brain, and this could explain its antidepressogenic effect."
It is free testosterone, or testosterone that is not bound to the proteins albumin and sex-hormone-binding globulin, that is biologically active (also called "bioavailable" testosterone). "In other words, if we wish to clarify what testosterone does, we need to look at free testosterone," said Dr. Almeida.
He noted, too, that while depression is more prevalent among women, the gap between the sexes "all but disappears" later in life. "Our findings may partly explain why that is so," he said.
Arch Gen Psychiatry. 2008;65:283-289. or http://www.medscape.com/viewarticle/571098