Dear Polly, probably not. There are dozens and dozens of possible causes of hair-loss, including simple aging, as increasing numbers of us discover every time we comb our hair ! This is not a probable side-effect of anti-depressants, so, although you don't mention which one you have been taking, it sems one of the least likely causes for the problem you've noticed. If its mild, its probably not going to be serious, and may not be worth worrying about. If it is marked loss of hair, and really bothers you, see your GP for a general check-up to explore some of the other many possible ( and more probable ) causes ) and he'll advise you on how to clear it up, based on whatever cause he finds.