For any drug you might care to name, there exists a range of very sensible reasons not to take it quite apart from its legal status. If someone doesn't want to take illegal drugs because of the laws against them and all the trouble they cause, or they want to avoid all or some drugs for spiritual or other reasons of their own, that's all well and good; for the rest of us, the question is whether the reasons for not taking any particular drug are good enough to outweigh the reasons for taking it. Most of the arguments on the plus side can probably be found in the individual nodes for the drugs. Here go the arguments against...
  • Alcohol
    Alcohol lowers inhibitions and clouds people's brains, making them much stupider and, on the whole, quite unable to sense their own stupidity; as a result they frequently do things they later regret. It makes people clumsy, inept, impotent, inarticulate and nauseous. It is also implicated in an alarmingly high proportion of road accidents and violence of all sorts, and kills people not just by making them murder each other and run each other over but also by making them choke on their own vomit, poisoning them, hardening their arteries and increasing the risk of getting diseases including heart disease and cirrhosis of the liver. Finally, alcohol is strongly addictive; it causes more personal damages to its addicts and those around them than perhaps any other drug besides heroin and crack; and hangovers are a bitch.

  • Tobacco
    Tobacco is highly addictive, smelly, unsatisfying, expensive and remarkably likely to lead to an early, painful death. It also accelerates many signs of aging, such as wrinkled skin and hardened arteries, and promotes infertility. Those at risk of death from tobacco include not just smokers but those who have to share rooms with them.

  • Caffeine
    Caffeine causes dependency in a remarkably high proportion of its users, making them irritable and unable to function properly in the morning until they have had a cup of coffee or tea. Caffeinated fizzy drinks are similarly addictive, hooking huge numbers of people - many of them too young to be considered responsible enough to start experimenting with any other addictive drug. Some people become jumpy and quick to anger while under the influence of caffeine. Too much caffeine can cause headaches, the shakes, and insomnia, as can abrupt withdrawal from the drug. As a stimulant, it is widely supposed that caffeine must be bad for the heart; surprisingly, however, epidemiological studies have on the whole failed to find an elevated risk of heart disease in its users. It may be that the natural antioxidants present in both coffee and tea are sufficient to counteract any negative effect - in fact, it looks as though tea in particular is actively good for the heart. Caffeine is still not recommended for people with known heart conditions, however.

  • Pain-killers
    The legal pain-killers - aspirin, paracetamol (acetaminophen), ibuprofen, codeine and so on - all have risks associated with them. Ibuprofen and especially aspirin can cause stomach irritation and gastrointestinal bleeding, and should never be taken on an empty stomach; aspirin is also implicated in Reye's Syndrome, so it should not be given to children; paracetamol can cause liver failure, and should never be taken with alcohol. Codeine is an opiate, and can cause dependence and sluggishness. In general, going to a pill at the first sign of a headache or similar tends to mean ignoring the root cause of the pain; most headaches have a simple and often easily treated cause, which pain-killers do nothing to address. The single biggest cause of headaches is certainly dehydration; unless you are sure the cause lies elsewhere, it's often wise to drink about a pint of water as soon as you feel a headache coming on. Hunger is another leading cause of headaches, so replenish your blood sugar and salt levels if you think you might need to; stress is another cause; tiredness is another; eye strain is another. Most headaches can be treated without recourse to drugs by addressing one or more of these issues. Many people feel that extensive use of drugs like pain-killers as quick fixes to problems instils an unhealthily drug-dependent outlook in children from an early age.

  • Psychiatric drugs
    Drugs are used more and more in psychiatry to treat an ever-growing range of diagnosable conditions, many of which it would never have occurred to anyone to think of as disorders a hundred years ago, twenty years, a decade. With every newly recognised condition come ideas about how to treat it with drugs; indeed, sometimes - as with anxiety disorders - the idea that there is something that is best seen as a disorder to be treated seems to have come about only after the invention of the drugs used to treat them. Many people are uneasy about this phenomenon, seeing it as a sign of the creeping medicalization of everyday life - based on a conception of normality which may itself be pathological. Many psychiatric drugs cause chemical dependence; most have long lists of side effects associated with them, of which both the prescriber and prescribee may be only peripherally aware. It is frighteningly common for psychiatric drugs to be prescribed and re-prescribed for conditions for which there is little or no evidence that they are effective; in some cases the drugs seem to be used as a 'chemical cosh' to keep patients quiet and make things a bit easier for those around them. There is evidence that the feelings of detachment which many patients feel while taking anti-depressants can lead some people to extremes of behaviour including suicide and - in a small number of cases - murder.

  • Cannabis
    Although some people find just the opposite, many people find that cannabis makes them lethargic and anxious (even paranoid). It can also cause or aggravate (or help cure or prevent) headaches, insomnia, panic attacks, depression, eating disorders, schizophrenic symptoms and boringness. Stoned people frequently report impaired short term memory, and certain tasks - chiefly boring ones - become much more difficult to concentrate on. Cannabis is usually smoked, exposing the user's lungs and airways to excessive heat, carbon monoxide, tar and a range of known carcinogens. In some parts of the world it is most often smoked with tobacco, with all the risks of addiction and disease that brings with it. However, whether cannabis smoking itself actually increases the risk of cancer or any other major fatal disease remains unclear; statistically, cancer rates do not seem to be any higher among long-term cannabis users than they are among the rest of the population.

  • Amphetamines (speed)
    Speed is known for its addictiveness and harsh comedowns. It almost certainly places an unhealthy strain on the heart, and the most common methods of ingesting it carry their own risks: Snorting any powder up one's nose does bad things to the mucous membrane; eating speed damages the lining of your stomach; rubbing into gums promotes tooth decay. Many ampthetamine addicts - speed freaks - become restless, irritable and paranoid. As with all stimulants, speed use is also very likely to lead to insomnia. Crystal meth, a refined amphetamine, combines a more powerful kick with correspondingly nastier side effects.

  • MDMA (ecstasy)
    Ecstasy seems to work by causing cells in the brain to release their stores of serotonin in a big burst, and then re-absorb it much slower than they usually would. Many users find that the surge of happy, lovey feelings this causes is matched by a bout of irritability, coldness and depression a few days later. Although not severe as these things go, this negativity is probably not something it's fair to inflict on those around you on a weekly basis. There is some tentative evidence that Ecstasy causes permanent changes in the brain, damaging serotonin transport fibres. However, the science is far from conclusive, however enthusiastically it may have been seized on by certain anti-drugs agencies; the key tests involved only 14 subjects, and even assuming the results were not a statistical aberration they failed to rule out other possible causes, such as the wide range of other drugs taken by most of the subjects. Another possibility is that the 'changes' detected could have been pre-existing differences which predisposed people to take drugs, and not damage caused by the drugs at all. This is not to say that ecstasy doesn't cause brain damage; but the truth of the matter is that at this stage nobody knows.
    Much has also been made of the sudden deaths of Ecstasy users; there is no mistaking that these occur, although the statistics suggest the average ecstasy user is about four times more likely to die in a car crash. In most cases the fatalities are caused not directly by the drug itself but by heatstroke caused by too much dancing, which is both more likely to occur and more likely to be missed in those on MDMA. Other causes of death include hyponatraemia, in which the blood thins and the brain swells; this was the condition which did for Leah Betts. It results from excessive water consumption, aggravated by the body's impaired ability to handle water while under the influence of MDMA. Finally, a tiny proportion of the population is at risk from something called serotonin syndrome when they take MDMA. This is a poorly understood, extremely rare reaction which results in shivering, rigidity and death.

  • Cocaine
    Cocaine turns people into arseholes. The boost it gives to a person's ego and self-confidence while they're under its influence makes many people insufferable. It also produces extraordinarily powerful psychological addiction, although it doesn't cause physical dependence; it is sometimes said that one of the main effects of cocaine is to make you want to take more cocaine, and this is only overstating the case slightly. Cocaine is thought to be extremely bad for the heart. Since it is usually snorted, cocaine can cause serious damage to the inside of the nose; it is said that in some coke abusers the septum rots away entirely. Cocaine is usually cut with other substances to increase its bulk; often this occurs at several stages between the producer and the eventual consumer. Mostly the powders it is cut with are relatively benign things like powdered glucose, but sometimes they are much nastier, and it's very difficult to guess what any given batch might have been cut with. Cocaine is also an exceptionally expensive drug, although it has come down in price in recent years, and surprisingly subtle and short-lived in its effects. It is implicated more strongly than any other drug in the funding of terrorists and other criminal organisations.

  • Crack (freebase cocaine)
    Crack is like cocaine, only more so; multiply the above arguments against cocaine severalfold, especially the bits about addiction and turning people into arseholes. Crack is also held to blame for much of the street crime in areas where it has taken hold, and its supply networks are largely controlled by ruthless, gun-wielding gangs.

  • Heroin
    The reasons for not taking heroin are so well-known that it almost seems pointless to reproduce them here. For completeness, here they are quickly: It is extraordinarily addictive, not just psychologically but physically; regular users are notorious for dropping out of society, being unable to hold down jobs, and funding their habit through theft, dealing or prostitution; it is frequently adulterated with ingredients which cause serious damage when injected into veins, and almost always adulterated with something; batches of pure heroin, when they do turn up, frequently catch people by surprise and kill them through overdose; the act of injecting potentially dangerous substances on a regular basis can do serious damage to a person's network of blood vessels; and the sharing of needles is one of the main routes by which HIV is passed from one person to another.

  • Psychedelic drugs
    Psychedelic drugs change who you are, by making you perceive things in ways which would never have been possible without them. They often seem cheap in terms of the money paid for them, but it is important to realise that the real price is paid mainly out of your sense of reality as you knew it. By no means is this is always a negative thing; people are often inspired to make positive changes in the way they live their life, and the new perspectives afforded by psychedelics have spurred many people to create art the likes of which would never have entered their mind if not for their experimentation with entheogens. However, a lot of people have ended up going a bit crazy, or indeed entirely crazy, and many are not entirely comfortable with the things they realise while under the influence. Psychedelic experiences are very often life-changing one way or another, so they should never be entered into lightly, and usually they should not be entered into at all by people who are not very comfortable with themselves and their surroundings. Regardless of longer-term changes, a bad trip is undoubtedly one of the most unpleasant and frightening things that can happen to a person. Here are some additional reasons not to take particular psychedelic drugs:

    • LSD (acid)
      Acid trips last much too long for many people: Up to about twelve hours, which is an incredibly long time to lose track of what reality used to be like, and long enough to leave the insecure wondering whether it will ever be like that again. Also, the novelty of pulsating ceilings and mind-bending time distortions often wears off after a few hours or so. The amount of LSD in one dose varies unpredictably between batches and between trips within a single batch (in its refined liquid form it is intensely powerful in tiny, tiny quantities). Finally, acid seems to be uniquely likely to lead to flashbacks years after the drug is taken, although these are far from common.

    • Psilocybin/psilocin (magic mushrooms)
      A mushroom trip is nothing like as long-lived as an acid trip (about six to eight hours), but it is still long enough that a mushroom trip which goes bad can be seriously traumatic. Also, stomach cramps are quite a common side-effect of magic mushrooms - particularly if eaten straight, rather than made into mushroom tea, and particularly if mixed with alcohol - and vomiting has also been known to result. With the intense awareness of bodily sensations that comes with psilocybin, things like stomach cramps - not to mention any pre-existing itches, aches and pains - take on a whole new dimension of unpleasantness.

    • Mescaline (peyote, etc.)
      The mescaline experience is somewhat longer than a mushroom trip, on average - 6 to 14 hours, according to my source. Also, the intensity of the trip caused by a given dosage is extremely unpredictable. The peyote cactus, the main traditional source of mescaline, is now an endangered species thanks to too many psychonauts digging up the slow-growing plants, and should only be considered as a source of mescaline by those with religious reasons to seek it out and those with access to peyote grown especially for the purpose. However, mescaline is also found in various other, more common species of cactus, some of which are quite popular as houseplants. The cacti themselves are quite bitter with an unpleasant texture, and aside from the very potent peyote cactus they all need to be consumed in quite substantial quantities. However, the grisliness of eating a chunk of fetid cactus flesh a foot long by three inches across can be avoided by extracting the drug first.

    • DMT
      Widely considered the most potent psychedelic in existence, DMT hits those who take it with an intensity unrivalled by other entheogens. The unstopping rush of bizarre imagery which swamps the senses has been known to convince people that they have just died; abject terror is not an uncommon feature of the DMT experience. The involved visions reported by many who experiment with DMT - for example, whole conversations with what appear to be alien beings or spirit guides - have led many to a shamanistic scepticism about consensus reality, which may or may not be healthy. A DMT trip lasts for only a few minutes, but they will probably be the longest and most intense few minutes of your life. Even more than other psychedelics, DMT is not recommended for people who are not secure in their sanity.

    • Salvia divinorum
      Salvia is the only major psychedelic which is not illegal in many Western countries. It is consumed in two forms: The dried leaves, which for most people take some persistence and good smoking technique to feel any strong effect from; and an extract derived from them. The extract is said to rival DMT in its intensity; since salvia trips last for somewhere in the region of an hour, this is a somewhat alarming prospect. By contrast, the leaves are sufficiently weak that you may feel as much effect from all the carbon dioxide in the smoke as you are from the divinorum itself. A salvia trip, especially the low-dose version, is a fragile thing, easily shattered by bright lights and walking around; so there is not much point taking salvia if there is anything else you want to be doing.

    • Ketamine
      Ketamine is a general anaesthetic as well as a hallucinogen, and perhaps doesn't really belong under the heading psychedelic. Along with intense visual hallucinations it causes feelings of numbness and dissociation from one's body , all of which some people find actively unpleasant. I have never heard of anyone on ketamine having the sort of psychological and spiritual insights reported by many of those who have taken the various other psychedelics mentioned here. What I have heard of, though, is people starting to see apparently meaningful connections between things everywhere they look, quite often accompanied by a feeling that they are themselves the nexus of these connections. Addiction to ketamine is not uncommon, and it is usually taken by snorting or injecting, with all the problems these cause. Finally, ketamine and its dissociative stablemates DXM and PCP can cause quite serious damage to the brain - see Olney's lesions.