Doctors have long assumed that diabetes--which strikes tens of millions of people--can bring on depression because of the difficulties it causes in the lives of sufferers, says the study’s senior author, Patrick Lustman of Washington University. But now, the idea that the reverse could be true--that is, that depression may lead to diabetes--is being seriously considered, says Lustman. One clue may lie in the inactivity and overeating that accompany depression. Each contributes to diabetes.