Researching the effects of drink and drugs on sex is tricky, involving sometimes reticent subjects whose memories may be unreliable.

But a review of years of studies on rats, published in Hormones and Behavior, confirms that stimulants and depressants form the chemical basis for numerous performance problems, from weak erections to premature ejaculation.

Stimulants (like caffeine and cocaine) and depressants (like alcohol) can sometimes act as aphrodisiacs at first, but interfere with crucial brain functions, says study author Jim Pfaus, Ph.D.