LSD: From Scientific Discovery to Prohibition — and Its Return to Mental Health Research

LSD: From Scientific Discovery to Prohibition — and Its Return to Mental Health Research

LSD is often associated with the counterculture of the 1960s, but its story actually began in a pharmaceutical laboratory. Long before it became a symbol of recreational drug use, scientists were studying LSD as a possible tool for understanding the human mind and assisting psychotherapy.

Today, after decades of limited research, LSD and other psychedelics are again being investigated in modern clinical trials. The renewed interest is important—but so is understanding the difference between psychedelic-assisted therapyand taking psychedelics without appropriate screening, preparation, supervision, and integration.

How LSD Was Discovered

Lysergic acid diethylamide, better known as LSD, was first synthesized in 1938 by Swiss chemist Albert Hofmann, who was working at Sandoz Laboratories in Basel, Switzerland. Hofmann was studying compounds derived from ergot, a fungus that grows on grains, while researchers were looking for potentially useful medicines. The compound was initially known as LSD-25 because it was the twenty-fifth substance in a series of lysergic acid derivatives. (PubMed)

Its unusual psychological effects were not recognized until 1943, when Hofmann was accidentally exposed to a small amount and experienced significant changes in perception and consciousness. Soon afterward, he intentionally tested the substance himself, beginning a completely new chapter in psychedelic science. (PubMed)

Sandoz later made LSD available to psychiatrists and researchers as an experimental substance. During the 1950s and early 1960s, researchers explored whether LSD could help scientists better understand consciousness, psychosis, personality, and the process of psychotherapy. (PubMed)

LSD and the Early Mental Health Research

Before its prohibition, LSD was studied in several areas of psychiatry. Researchers investigated its possible role in anxiety, depression, alcohol dependence, psychosomatic conditions, and psychotherapy. (PubMed)

Two broad therapeutic models emerged. In one approach, relatively lower psychedelic doses were sometimes used across multiple psychotherapy sessions to facilitate emotional exploration. Another approach involved fewer but more intense psychedelic sessions surrounded by psychological preparation and follow-up therapy.

Importantly, LSD was generally not viewed simply as a medication that a person would take on their own. Even early researchers recognized that the person's psychological state, relationship with the therapist, expectations, environment, and subsequent processing of the experience could strongly influence the outcome. (PubMed)

Some early studies reported encouraging results, but many were conducted before today's standards for randomized controlled trials, standardized diagnoses, adverse-event reporting, and research methodology existed. This makes the older literature scientifically interesting, but difficult to compare directly with modern clinical trials. (PubMed)

Why Was LSD Banned?

The common explanation is that LSD was prohibited simply because governments considered it dangerous. The real history is more complicated.

During the 1960s, LSD moved rapidly outside laboratories and clinics and became closely associated with the counterculture movement and widespread nonmedical use. Political concern about psychedelics increased dramatically. At the same time, pharmaceutical research regulations were becoming much stricter. (PubMed)

Researchers also faced genuine scientific problems. Psychedelic experiences are extremely obvious to participants, making traditional double-blind placebo-controlled trials difficult. Therapeutic outcomes were also influenced by psychotherapy, expectations, environment, and the relationship with the therapist, which complicated attempts to isolate the effect of the drug itself. (PubMed)

Sandoz stopped distributing LSD for research in the mid-1960s, regulations became increasingly restrictive, and nonmedical use became prohibited in the United States in 1970. LSD was placed in Schedule I under the Controlled Substances Act, and research largely disappeared for decades. (PubMed)

So the collapse of LSD research was caused by several overlapping factors: political controversy, uncontrolled recreational use, increasingly strict regulation, and weaknesses in the scientific evidence available at the time. It was not the result of one simple scientific conclusion that LSD had no therapeutic potential. (PubMed)

Why Scientists Became Interested Again

Modern psychedelic research began to re-emerge under far stricter scientific and ethical standards.

One randomized controlled study examined LSD-assisted therapy in people experiencing anxiety, including individuals living with serious illnesses. Participants received LSD within a structured therapeutic protocol rather than taking the drug independently. Researchers reported significant reductions in anxiety that remained detectable months after treatment. (PubMed)

An earlier pilot study involving people experiencing anxiety related to life-threatening disease also found reductions in anxiety following LSD-assisted psychotherapy, although the study was very small and therefore could not provide definitive evidence. (PubMed)

Systematic reviews of historical and modern LSD research have found potentially encouraging signals for anxiety, depression and substance-use disorders, but researchers continue to emphasize that the evidence base remains much smaller than that for established psychiatric treatments. (PubMed)

More broadly, research involving psychedelics such as psilocybin, LSD, MDMA and related compounds has renewed scientific interest in their possible role in depression, anxiety, PTSD and other conditions. However, these are still evolving areas of clinical research rather than simple replacements for existing mental-health treatment. (PubMed)

A Psychedelic Experience Is Not the Same as Psychedelic-Assisted Therapy

This distinction may be the most important part of the discussion.

In clinical research, participants typically do much more than simply take a psychedelic substance.

Protocols may involve:

• medical and psychological screening before participation;

• evaluation of medications, physical health and psychiatric history;

• preparation sessions before the psychedelic experience;

• a controlled environment;

• trained professionals remaining present during the experience;

• monitoring of psychological and physical responses;

• psychological support if fear, confusion or distress emerges;

• follow-up and integration sessions afterward.

Modern psychedelic-assisted therapy research therefore investigates a whole therapeutic process, not merely the pharmacological effect of a drug. (PubMed)

This is also why describing psychedelics as medications that someone can simply take by themselves to improve mental health can be misleading.

Why Unsupervised or Repeated Use Can Be a Problem

LSD can produce extremely powerful alterations in perception, emotions, sense of self, memory and thought. Controlled studies in healthy participants have shown that higher doses produce greater psychological effects and can increase anxiety, heart rate, blood pressure and body temperature. Some participants have also reported temporary flashback-like experiences. (PubMed)

Importantly, the relatively reassuring safety findings often quoted from psychedelic research come primarily from carefully screened participants in controlled research environments. That is very different from uncontrolled use in the community. A 2024 safety meta-analysis found a low rate of serious adverse events in psychedelic psychotherapy studies, but specifically emphasized that these results occurred in controlled settings with appropriate inclusion criteria. (PubMed)

Researchers are also paying increasing attention to adverse psychological outcomes and the need for better monitoring. People with certain psychiatric vulnerabilities—including psychotic disorders—are commonly excluded from psychedelic trials because of concern that psychedelics could worsen or trigger psychiatric symptoms. (PubMed)

Even microdosing should not automatically be considered a proven mental-health intervention. In a randomized study involving repeated low doses of LSD, researchers found no lasting improvement in mood or most cognitive outcomes. Another randomized study found temporary subjective changes on dosing days but no persistent improvement in overall mood or cognition after six weeks, and several participants withdrew because of anxiety. (PubMed)

More is therefore not necessarily better—and repeated psychedelic exposure should not be confused with evidence-based psychedelic-assisted therapy.

The Importance of Preparation and Integration

Psychedelic experiences can bring forward powerful emotions, memories, fears, personal beliefs and shifts in identity.

Having an intense experience is not necessarily the same as healing.

The potential therapeutic value may depend partly on what happens before and after the psychedelic experience: psychological preparation beforehand, a safe and supportive environment during it, and careful integration afterward.

Integration allows a person to explore what happened, differentiate meaningful insight from temporary altered-state thinking, understand difficult emotions, and translate useful insights into everyday life.

Recent research examining psychedelic-assisted psychotherapy continues to treat psychological preparation and integration as central components of the treatment model. (PubMed)

The Responsible Perspective

The return of psychedelic research should not lead us back to the uncontrolled experimentation that contributed to the field's collapse decades ago.

The lesson from LSD's history is almost the opposite.

These compounds deserve serious scientific investigation precisely because they are psychologically powerful.

Current research suggests that LSD and other psychedelics may eventually have valuable roles in mental-health care for carefully selected people, but the therapeutic model being studied is generally structured, screened, supported and monitored. (U.S. Food and Drug Administration)

Taking LSD repeatedly or attempting to treat trauma, depression or anxiety independently is therefore not equivalent to psychedelic-assisted therapy and should not be presented as such.

And simply having someone described as a “psychedelic assistant” nearby is not enough. For mental-health treatment, the relevant support should come from appropriately trained and qualified professionals working within a legal and ethical framework, with screening, preparation, safety planning and integration.

The future of psychedelic mental-health care is unlikely to depend on encouraging people to take more psychedelics.

It will depend on learning when these substances may help, who may benefit, who may be harmed, and how they can be used responsibly within evidence-based care.

Educational note: This article is intended for general information and does not encourage or provide instructions for using LSD or other controlled substances. Psychedelic research remains an evolving area of medicine, and individual risks can vary substantially. (PubMed)