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Low Testosterone Linked to Depression in Elderly Males
> 3/7/2008 3:01:04 PM

The greater vulnerability of women to depression has been the subject of many hypotheses. Some have suggested a social difference, perhaps comprised of the unique pressures facing women, while others have posited a biological difference such as divergent brain-structures or sex hormones. A study this month in the Archives of General Psychiatry lends credence to the last of these explanations.

Lead researcher Dr. Osvaldo Almeida took blood samples from 3987 men aged 65 and older. They were recruited not from a single, or even multiple, communities but rather from a random pool generated from electoral rolls. Even so, a geographically transcendent correlation emerged between low levels of free testosterone and high levels of depression. The men were asked to self-evaluate their mood on the 15-item Geriatric Depression Scale, and those who scored in the highest quartile of depression were 3.12 times more likely to be in the lowest quartile of free testosterone.

These results are so valuable because of the great lengths to which Dr. Almeida went to correct for confounding variables. This is crucial, because there are many health problems and social factors that can affect both mood and hormone levels. In fact, the general ravages of age were found to decrease both mood and testosterone, so it was adjusted for, along with educational level, smoking, BMI, cognitive impairment, and previous treatment for depression (in case the side-effects of antidepressants somehow altered body chemistry). Dr. Almeida also caught a subtle personality difference, finding that subjects with depression were 2.17 times less likely to consent to a blood test in the first place. Previous work, such as the Rancho Bernardo Study by Barrett-Connor, found an inverse relationship between Beck Depression Inventory scores and free testosterone, but they did not take confounding variables into account adequately.

The correlation between depression and testosterone was not linear. Rather, the risk creeps up almost imperceptibly until testosterone falls below 6 ng/dL, after which a subject's vulnerability skyrockets. This critical threshold makes the information more helpful for treatment. Doctors may soon be able to identify patients at high risk for depression with a simple blood test. It is not yet clear which way the chain of causation goes. If low testosterone causes depression, then supplemental injections may protect them and restore the confidence that these patients presumably enjoyed as young men.

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