Hands up whose dick has physically shrunk after taking drugs. Not just cold-swimming-pool small, but worryingly small, to the point where it is but folds of skin bunched up and fastened awkwardly to your crotch; a thumb and little finger job; the kind of thing you don't want to tell a single soul about – bar all of Reddit when you're searching for some reassurance.
No? If not, you'll definitely be familiar with the other common effect of drugs on the male anatomy: the unresponsive flaccid penis. This is an unfortunate one, because a lot of drugs famously make you want to fuck, but also completely swipe away your ability to do so. But which substances are the worst for this, and why?
"If you think of erectile physiology, you need blood flow, so anything that restricts blood flow is a bad thing," says John P Mulhall, Director of the Male Sexual and Reproductive Medicine Program at Memorial Sloan Kettering Centre in New York. "Like adrenaline: it's a tremendous blood flow restrictor, so anything that would function similarly to adrenaline – MDMA, for instance – could be extremely bad for your erectile function."
Mulhall and I have spent the last 20 minutes discussing the science of turgidity. Brilliantly, his favourite quote is: "You're only as good as your last erection." I'm trying to find out which drugs are the worst for your dick, and he's keen to state that there's been very little research done in this area. "We're mostly working with basic principles, then anecdotal evidence from patients," he says, but adds: "But I think there are serious negative effects of drugs like ecstasy and crystal meth. I think we can make a presumptive link between the two and erectile disfunction."
MDMA and ecstasy are typical of that great paradox I mentioned. With all the serotonin – the "joy chemical" that ecstasy releases – firing from your serotonergic system, you're turned into a fawning, cuddling mess, flushed in love and lust with the world and its inhabitants. "All stimulants have a global effect on all areas of the brain to enhance function, so that would enhance the libidinal drive," says Tim Williams, Clinical Director at Bristol Specialist Drugs and Alcohol Service.
But as Mulhall explained, the MDMA that's making you all cuddly and lustful is exactly what can prevent you from taking it any further. The drug works as a vasoconstrictor, narrowing blood vessels to, among other places, your penis. Which is why it can retract or becomes almost entirely useless. You also might not have been able to urinate while on MDMA before. That has nothing to do with the penis or the narrowing of your vessels, but with MDMA releasing the hormone vasopressin, which controls the kidneys' retention of water.
Being a potent stimulant, cocaine will likely also make you want to have sex, and then potentially prevent you from doing just that for the same vasoconstrictor-y reasons. But there are also some pretty appalling theories about long-term periods of cocaine use effectively shutting down your engines permanently.
"Cocaine is a really nasty drug in the brain," says Mulhall. "It causes blood vessels to constrict, and therefore you get a lack of oxygen to regions in the brain. There's some evidence in people who have died who've had long-term cocaine habits that they've got lots of these little bits of brain death, so obviously that will affect lots of regions. If you get a bit of death that affects the libidinal system, that will absolutely cause problems there."
"I think when you speak to people about cocaine they'll often say [sex] is way better," says Mulhall, which would appear to fall in line with a 2002 study that found 40 to 50 percent of respondents experienced an increase in sex drive, fantasies, pleasure, performance, obsession and unusual or risky sexual behaviours while using coke. "But it's really a perceptual issue. I don't think there's anything to be gained – from an erectile function standpoint – in any of these agents [drugs] in the short or long-term."
What of the dreaded mid-sex flop? That moment when you've managed to actually get it up and working, only for it to desert you the minute you change position or get distracted while thinking about something inane?
"Again, that's adrenalin," says Mulhall. "You see these problems in people with ADHD. They're easily distracted, they lose focus. It's the same thing with an orgasm. An orgasm occurs most readily when you're in the zone, and if you're not in the zone it's a problem. People with erectile dysfunction sometimes can also become spectators of their erection. So you're thinking, 'How am I doing. Am I doing it right?' Again, that can take them out of the zone."
Both Mulhall and Williams agree on the devastating effect that alcohol can have on your dick – "There's much better data on alcohol's effect on erectile function," says Mulhall – and when you consider that a global drug survey suggested that 80 percent of cocaine users drank while using the drug, it's not evidence to be disregarded.
"It's a social lubricant, so there's increased levels of relaxation, but every person is going to have a different threshold dose, beyond which it's going to suppress the central action of the brain," says Mulhall. "It's a central depressant, so it's going to have a negative effect at a certain dose on the brain centres that trigger erections. They're like the sparks that get everything going. You need them."
Of course, people do try to have sex on drugs other than ecstasy and cocaine. What about, for instance, ketamine? At small doses – "a small bump", according to Williams – it would enhance brain function, essentially "enhancing the libidinal drive". Any more than that, however, and the dissociative nature of it means bumping uglies is the last thing on anyone's mind.
As for weed, there's little in the way of data available, though a recent pilot study in the US suggested that the illegality of weed perhaps contributed to the facilitation of sex. "I've never seen any research to show that cannabis is associated with reduced sex drive and function," says Williams. "However, there is an a-motivational syndrome prevalent in heavy cannabis use. So you might be demotivated to go to school, leave the house, go to work or exercise. I wouldn't have thought it would help."
One question remains: is there anything we can do to help things along, beyond resorting to Viagra, which – when combined with drugs – plays a savage tug of war with your cardiovascular system?
"The best advice if you really want to have an erection?" Mulhall asks. "Don't use those drugs."
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