F*cking While F*cked Up
Take, for example, alcohol. Alcohol, as everyone knows, tends to decrease people's inhibitions, making them feel more relaxed and more open to certain activities (e.g. sex). Alcohol is a depressant and so its main effect on the body is to slow all processes down, however, too much and you could end up feeling too relaxed to bother. Generally speaking, a small amount of alcohol appears to increase sexual desire, however consumption of large amounts of alcohol can have the opposite effect, and for men can make it difficult to maintain an erection. As Shakespeare put it, "It provokes the desire but takes away the performance." This is because alcohol decreases the production of testosterone in men, which is necessary for the physical arousal response. In women the effect is actually the opposite, testosterone production is increased and as a result women tend to feel more sexually aroused when drinking, although the physiological signs of arousal are actually decreased. Large quantities of alcohol can also make orgasms difficult to achieve or make the sensation of orgasm less intense for both men and women, although some women report increased intensity of orgasm after alcohol consumption. For women who experience stronger orgasms, the trick may be alcohol's relaxing effects, rather than a physical reaction. In other words, the effect alcohol has on your sex drive and performance depends on how much you drink and the ways your individual body reacts to alcohol. Unfortunately, because it lowers inhibitions, alcohol also increases risky behavior. People under the influence of alcohol are less likely to use protection. Alcohol is also a factor in many rapes, not just because of women getting too drunk to defend themselves, but unfortunately also because of men getting too drunk to realize the person they're having sex with didn't consent (always check for enthusiastic consent, guys, and girls for that matter, especially if you've been drinking).
Marijuana's effects on sex are similarly complex. Surveys of marijuana users indicate that sometimes the drug enhances the sexual experience, while other times its effect is neutral or even negative. The majority of survey respondents report increased desire when under the influence of marijuana, with women reporting an increase at slightly higher levels than men (50% of women to 39% of men, according to one survey). Marijuana, like alcohol, also lowers inhibitions and has a relaxing effect, which may make people more receptive to sex. Low doses of marijuana can create the impression that the sense of touch is heightened, which can obviously have a strong impact on sexual enjoyment. Higher doses of marijuana, however, can have a depressive effect and therefore decrease sex drive for the same reason as alcohol - it lowers testosterone levels. Also like alcohol, marijuana use can lead to the questionable decision to have unprotected sex.
Data on harder drugs is difficult to come by, possibly because researchers are more focused on general effects of drug use and how to keep people from taking such rather than exploring their effect on sexual function. Users of ecstasy do report higher levels of sensation and sexual desire, although orgasm was delayed, and erectile dysfunction was not uncommon (reported by 40% of men). Cocaine, a heavy stimulant, appears to increase sexual desire in the short term while having a negative impact on sex drive with long-term use. Heroin and other opiates are depressants, and therefore can be expected to have a negative effect on sex drive (once again, the reason is reduced testosterone levels), especially with long term use, but as always your mileage may vary. How cocaine and heroin actually make sex feel while your having it isn't clear from the scientific literature (and I don't recommend testing it out for yourself).
If you're looking to increase your sexual pleasure with intoxicating substances, the bottom line seems to be that moderation is key. Small amounts of both alcohol and marijuana can have an enhancing effect on sexual arousal, but too much and you've effectively screwed yourself (in the bad way). It's also important also to be extra vigilant about protection if you're using any such substance and having sex with someone who isn't an established monogamous partner. Yes, you really do need that condom, I don't care how relaxed and carefree you feel. A little lube might come in handy too, since alcohol can reduce physiological signs of arousal in women and marijuana tends to dry out mucous membranes (i.e. both can leave a girl a little too dry for comfort). Other than that, as long as it's an occasional enhancement and not a crutch, then go ahead and indulge. Science says it's okay.
Dr. Pisaster has a doctorate in biophysics, not actually anything sexy. She does however enjoy having sex, reading about sex, and talking about sex. Especially when she's had a little whiskey.