LSD is a very unstable chemical, and it is therefore difficult to produce. Because the dose necessary for intoxication is so small, the majority of LSD is produced by a relatively small amount of large-scale specialist manufacturers.
LSD caused a number of scare stories in the media in the 1960s, and governments were under pressure to criminalize possession of the then popular drug. It is controlled internationally by the 1971 UN Convention on Psychotropic Drugs, which means it is illegal except for scientific usage. It is a Class A drug in the UK and a Schedule 1 drug in the USA.
Before it became popular as a recreational drug, LSD was advocated and used by psychotherapists to treat patients. A notable proponent was actor Cary Grant. Currently LSD and a related non-psychoactive compound Bromo-LSD is believed to be the only known cure for cluster headaches, an extreme form of migraine.
LSD is a powerful psychedelic and its effects are very much dependent on the mental state of the user and the environment in which the drug is taken, respectively known as “set” and “setting.” It can produce a state of highly altered consciousness and perception, often subjectively described as a spiritual experience. It can make everyday experiences seem more vivid and extraordinary. LSD has significantly decreased in popularity since the 1960s, possibly due to the large amount of urban legends surrounding it, such as that it can be adulterated with strychnine, or that it can cause the user to think they can fly and jump off a building.
LSD has almost no physical side effects, and is a non-toxic substance, so overdose is nearly impossible. A high dosage or use in an unsuitable setting can however result in an overwhelming experience, including panic, confusion and despair. LSD can last up to 12 hours and so this can be extremely unpleasant. In users with pre-existing psychological problems it could trigger a psychotic episode. Changes in perception can also lead to harm done to the user, not by the drug but through unsafe behaviour.