Older men with lower levels of testosterone in their blood appear to have a higher prevalence of depression, a new study shows.

Depression affects between 2 percent and 5 percent of the population at any given time and women are more likely to suffer from depression than men until the age of 65, when sex differences in depression rates almost disappear. Several studies have suggested that sex hormones might be responsible for this phenomenon.

Dr. Osvaldo P. Almeida, from the University of Western Australia in Perth, and colleagues studied 3,987 men between 71 and 89 years of age who had their testosterone levels measured.

The overall prevalence of depression in the group was 5.1 percent, the investigators found.

They also found that men with depression had significantly lower testosterone levels than did their non-depressed peers.

After adjusting for factors that might influence the results, such as age, physical disability, smoking, body weight, and cognitive test scores, men in the lowest quintile (20 percent) of testosterone concentration had three times the odds of having depression compared to men in the highest quintile.

“These findings suggest a causal relationship,” the investigators conclude. If confirmed in a randomized trial, older men with depression may benefit from testosterone screening, and testosterone supplementation may contribute to the successful treatment of older men with low testosterone levels and depression.

SOURCE: Archives of General Psychiatry, March 2008.