LSD is a hallucinogenic drug which distorts the way the mind perceives things. Its effects are usually felt within half an hour of use and last for up to 12 hours. Experiences vary according to the individual so are difficult to typify.

Users report that objects appear much brighter and may seem to be moving or distorted. Hearing may also be intensified and the user's feeling of time and place may be distorted. Once a 'trip' has begun, it is impossible to stop or control it. The drug tends to exaggerate the mood a person is feeling when they take it. Users do not become physically dependent on LSD, but some may experience a psychological dependence. Some develop a tolerance of the drug and need to take higher and higher doses, but deaths and overdose are rare.

LSD users sometimes experience flashbacks which may distress them. It has also been linked with long-term psychiatric illnesses, such as schizophrenia. Magic mushrooms also have a hallucinogenic effect which is generally milder than that associated with LSD. However, the physical effects are generally more pronounced, such as increased heart rate and blood pressure. Side effects include nausea, vomiting and stomach pains. Long-term effects may include flashbacks, but little research has been done in this area.

There are reported to be no withdrawal symptoms and no risk of physical addiction.