Depression and low testosterone are common in middle-aged and older men and both are linked to bad sex. Researchers from the Department of Psychiatry at the University of Toronto found that depression was a better marker of sexual dysfunction than low testosterone levels. Testosterone levels and sexual problems were assessed in depressed and non-depressed middle-aged men.
Poor sexual performance was most common in depressed men with low testosterone levels. Sexual problems were less prevalent in non-depressed men with low testosterone, which showed that depression was a more common cause of bad sex than low testosterone. (Journal Sexual Medicine, 7: 816-825, 2010)