Those who take hallucinogens — primarily LSD users — occasionally reexperience events or sensations from trips long after the effects of the drug have worn off. Such flashbacks may occur many weeks or even many months after the use of the drug. People who have experienced flashbacks describe them as being as vivid as the initial experiences, although they are aware that they are experiencing a flashback, not a real LSD trip.

Several studies focusing on flashbacks experienced by LSD users indicate that between 25 and 30 percent of those who take LSD have experienced flashbacks at least once. Ten percent of those found them frightening, although none felt that they were actually in danger. The majority reported that the flashbacks did not disrupt their normal routines; a few even said they found the flashbacks pleasurable.

No one knows what causes flashbacks. The first attempts to explain them suggested that minute amounts of LSD had somehow been “trapped” unabsorbed in the user’s brain and had dislodged. More recently, however, this theory has been undermined by research that suggests that some flashbacks are triggered by the use of other drugs such as alcohol or marijuana. Still other researchers believe that flashbacks are the result of various forms of stress such as sleep deprivation or a traumatic experience such as the death of a family member or loss of a job.

Some researchers, however, believe that flashbacks may not be caused by LSD at all. They assert that almost everyone experiences flashbacks, which are simply vivid memories of intense emotional experiences. Many people who have never used hallucinogenic drugs report having flashbacks of events such as an automobile accident, the funeral of a close friend or relative, or some violent incident in which they were involved. Soldiers who have experienced combat sometimes report the same fear and panic of battle overcoming them many years after returning home from war. Since LSD trips can also generate intense emotions, these researchers conclude that no differences exist between flashbacks of LSD trips and other memories of significant events. The question of flashbacks and many other unanswered questions associated with LSD use lie at the heart of why LSD use continues to be of concern to the medical profession.

LSD also continues to be of concern to law enforcement authorities, yet few people are actually prosecuted for possessing the drug. In part, this is because the small quantities in a dose of LSD make it easy to conceal. In part, too, authorities have made a conscious decision to devote their limited resources to eliminating what they see as a much more serious problem: rave drugs.


The 1960s LSD culture in the San Francisco Bay area produced more than its fair share of cultural icons. One who played a major role was Augustus Owsley Stanley III. Known simply as Owsley to the locals, he was the primary producer of LSD in 1964 before the recreational use of LSD was declared illegal.

During the early ’60s when LSD was still legal, few people making it paid careful attention to precisely mixing the chemicals. Many amateur chemists failed to get the mixture right, and the resulting compounds made people very sick or failed to induce hallucinations at all. The other problem was that the doses required to create hallucinogens were so small that precise measurements were hard to perform. As a result, users never knew if the dose was the 200 micrograms advertised or double that amount. Owsley’s fame throughout the San Francisco area was based on his precise mixing of the chemicals as well as his accurate dosage.

Owsley hired a chemist from the University of California in nearby Berkeley to make sure his LSD was pure, and he quickly acquired the reputation as a reliable maker of LSD. Many people buying LSD demanded that it be made by Owsley because it was considered reliable. Owsley was the first person to buy a professional press for making pills, and he guaranteed that each pill would contain exactly 250 micrograms of LSD. In keeping with the psychedelic spirit of the times, he manufactured the pills in many different colors and gave each a distinctive name, such as “yellow submarine” and “purple haze.”

Owsley charged two dollars a dose, and those prices never changed. Even when LSD was declared an illegal substance, Owsley continued to make LSD. He was not in the business for the money, and everyone respected him for that Cheryl Pellerin quotes Owsley in her book Trips: How Hallucinogens Work in Your Brain: “I never told anybody to go out and take it… but… I wanted to take it… and I didn’t want to poison myself. I didn’t like Russian Roulette with chemicals.”