A dose of the hallucinogenic drug lysergic acid diethylamide or LSD, commonly referred to as acid, is an effective way to treat alcoholism, according to Norwegian researchers who analyzed results previous studies.

Researchers at the Norwegian University of Science and Technology examined results of six U.S. and Canada studies between 1966 and 1970, and found that patients who received a large dose of LSD were less likely to relapse into problematic alcohol use and had higher levels of total abstinence.

Researchers said many of the LSD patients had also reported that they had new insights into their addiction with alcohol and were more motivated to address their alcoholism. 

"In independent and standardized follow-up examinations, ranging from one to twelve months later, all of the studies showed that the patients who had received a full dose of LSD fared the best. On average, 59 per cent of full-dose patients showed a clear improvement compared with 38 per cent in the other groups," co-authors Teri Krebs and Pål-Ørjan Johansen wrote in their analysis.

LSD patients had also reported greater self-acceptance, openness and faith in their ability to cope with their future problems.

LSD has been used in many experiments as treatment for various disorders, including alcoholism in the 1950s to 1970s, but not all of them were scientifically applicable to modern standards.  Researchers said that the six studies chosen in the recent analysis are scientifically plausible by today's standards.

All of the six studies involved the same treatment program and involved a total of 536 people. Participants had either been given a single large dose of LSD, small dose of the stimulant or none.  While all studies encouraged patients to reflect on their alcohol problem, some of the studies had patients talk with a therapist and other studies only gave participants brief reassurance if the patients wanted it.

Researchers said all the studies were also blind, meaning neither participants nor researchers administering the doses had known in advance which patients would get a full dose of LSD.

The analysis found that the results from all the studies pointed in the same direction, that a single dose of LSD helped severe alcoholics with their addiction problem and made relapse less probable.

"There has long been a need for better treatments for addiction. We think it is time to look at the use of psychedelics in treating various conditions," the authors wrote.

Researchers are still unsure as to why LSD helped with alcohol addiction but they speculate that the effects stem from how LSD interacts with certain groups of serotonin receptors designated the 5-HT2 receptors in areas of the brain involved in mood, cognition, perception and in parts that receive sensory signals from external stimuli.

"We do not yet fully know why LSD works this way," researchers noted. "But we know that the substance is non-toxic and that it is not addictive. We also know that it has a striking effect on the imagination, perception and memories."

"LSD may stimulate the formation of new connections and patterns, and generally seems to open an individual to an awareness of new perspectives and opportunities for action," they said.

The U.S. had banned LSD had been banned for recreational use in 1970.  While the drug was and is still permitted as an experimental medical treatment, the researchers said that it is becoming increasingly difficult to conduct LSD clinical trials because many have claimed that the stimulant had demonstrated no medical use.

"The earliest studies reported promising results but also had methodological problems. Many scientists expected unrealistically good results from a single dose, and tended to ignore effects that lasted less than a year. Importantly, many of the individual studies did not have enough patients to reach a conclusion by themselves," they wrote.

"But when we combine studies that had sound methodology, the results are unambiguous. We can therefore safely conclude that a single dose of LSD had a positive treatment effect that lasted at least six months," Krebs and Johansen noted.

Researchers said that the therapeutic effects of a single dose of LSD was the most effective during the first few months, and as the time went on the effect gradually decreased.

"It is unusual for psychiatric drugs to have an effect that lasts for several months after a single dose. We now better understand that alcoholism is a chronic, relapsing disorder that typically requires ongoing treatment. The next step should be to periodically provide additional doses of LSD in combination with modern evidence-based treatment programs," the researchers said.

"There has long been a need for better treatments for addiction. We think it is time to look at the use of psychedelics in treating various conditions," they concluded.

The meta-analysis is being published in the Journal of Psychopharmacology.