Here's a bummer of a news bulletin from the American Journal of Psychiatry (via Reuters Health): Women are more likely than men to inherit a predisposition for major depression.

The news comes from a study of the national Swedish Twin Registry, which found that "the heritability of liability to major depression was significantly higher in women (42 percent) than in men (29 percent)."

The study results suggest that the genes that impact depression may be slightly different in men than in women -- and that the difference may be attributable to PMS and childbirth.

One of the researchers, Dr. Kenneth S. Kendler, put it this way, "We have pretty good evidence that there is a set of women that are prone to depression, particularly in the postpartum period and during the premenstrual phase of the menstrual cycle." What it may boil down to, he said, is that depression runs in families, but women's hormonal fluctuations make them more susceptible to inheriting it.

Ouch. Look for chauvinist nut jobs to amp up their "women's periods make them crazy" rhetoric in a blogosphere near you!