LSD is a remarkably non-toxic drug, with few (if any) adverse physical effects. The estimated LD50 (dose at which 50% of subjects die) for humans is estimated at 12,000-14,000mcg LSD. There are reports in the literature of individuals ingesting 40,000mcg of LSD and surviving unscathed.

There have been NO recorded fatalities as a result of LSD intoxication alone. All deaths have been associated with poly-drug use or accidents as a result of intoxication. LSD has rarely (and controversially) been implicated in suicide. There are some reports of hyperthermia syndromes with LSD, but again these have only been reported with doses of LSD in vast excess of normal.

(Coma, Hyperthermia, and Bleeding Associated with Massive LSD Overdose, A Report of Eight Cases Klock JC, Boerner U, Becker CE : Clinical Toxicology, 1975; 8(2):191-203)

Even when used repeatedly over long periods of time LSD is not addictive and there is no withdrawal syndrome on discontinuation of use. However if LSD is used daily for several days tolerance to its hallucinogenic effects will build up, meaning a user requires larger doses of LSD to achieve the same result. This tolerance disappears if LSD is abstained from for several days. Cross-tolerance to mescaline and psilocybin also occurs.

Other than accidents, acute dangers of LSD are limited to a person being unable to cope with the thoughts and feelings engendered by the trip. Sometimes people can enter confusing and frightening states, with time loops and distortions which they feel unable to deal with. This is colloquially known as a “bad trip”. Although frightening for a LSD user this is a temporary state that very rarely requires medical intervention.

As with any drug LSD can exacerbate pre-existing mental health problems, including depression. Some LSD users have experienced what is clinically referred to as “LSD Psychosis”, a schizophrenic-type disorder that appears to have been triggered by the drug. However, in careful analysis of LSD psychosis patients, it appears that those who have strong family histories of major psychosis or psychopathology are more vulnerable than those who do not.

In a survey of five-thousand individuals who had used LSD a total of twenty-five-thousand times, Cohen (1960) found 1.8 psychotic episodes per thousand ingestions, 1.2 attempted suicides, and 0.4 completed suicides -- figures consistent with the those of the general population, which means that psychotic episodes could not be attributed to LSD.

(See Here…

There was a study done in 1967 which reported that LSD could cause chromosomal breakage. This has subsequently been disproved by numerous other studies.

(See Here: …

“Flashbacks” associated with hallucinogen use are often referred to in sensationalist news articles. The term refers to a transient recurrence of disturbances in perception that are reminiscent of those experienced during one or more earlier “trips”. The person must have had no recent hallucinogen use and must show no current drug toxicity. The symptoms cannot be attributable to a general medical condition and cannot be better accounted for by another mental disorder. They are otherwise referred to as “Hallucinogen Persisting Perception Disorder”. The frequency of flashbacks is controversial with quoted figures in the literature ranging from 15-77%!

(See here about LSD flashbacks: Flashbacks in Theory and Practice)