Long term effects
There are few known long term effects from hallucinogens. However, ‘flashbacks’ – times when you feel the effects of the drug again – can happen days, weeks or even years after taking the drug.
Flashbacks can include visual hallucinations and other effects. They can happen without warning, last for a minute or two and can be disturbing.
Flashbacks may be triggered by using other drugs or by stress, tiredness or physical exercise.
Regular users are more likely to experience flashbacks than people who only use the drug from time to time.
Some other long term effects of hallucinogens may be damaged memory and concentration.

Using hallucinogens may increase the risk of mental problems in some people.

Hallucinogens and pregnancy
LSD may be related to an increased risk of miscarriage, but little is known about the effects of LSD in pregnancy.

Tolerance and dependence
Anyone can develop a ‘tolerance’ to hallucinogens.
Tolerance means that you must take more of the drug to feel the same effects you used to have with smaller amounts. With hallucinogens this happens very quickly. Being tolerant to one kind of hallucinogen (eg LSD) can also make you tolerant to other kinds (‘magic mushrooms’). Tolerance goes away when you stop using the drug regularly.
‘Dependence’ means that a drug takes up a lot of your thoughts, emotions and activities.
‘Withdrawal’ means that if you stop or greatly reduce your intake of the drug, you will experience uncomfortable physical and mental signs.

There is little evidence that dependence or withdrawal syndromes exist for hallucinogens.

Hallucinogens and the law
Using hallucinogens is illegal. If you use, sell or give hallucinogens to someone else and get caught, you could face substantial fines and penalities including a prison sentence.

Hallucinogens and driving
Hallucinogens change the way you see, hear, touch and experience other sensations, making it very dangerous to drive. It is illegal to drive under the influence of drugs, including hallucinogens.

Penalties include losing your licence, a fine and/or jail.