London - It was the drug of choice for hippies looking to turn on, tune in and drop out during the late Sixties.
But LSD may not have been as mind-blowing as many revellers who took it believed, researchers claim.
A study has found that those given a placebo – an inert tablet such as a sugar pill – can be persuaded they are undergoing the same mind-bending experience as they would if they had taken hallucinogenic drugs such as LSD or magic mushrooms.
It means some who believed they had ‘taken a trip’ may have felt high due merely to the atmosphere of the party or event they were at. The same may apply to the "rave" drugs taken at acid house parties in the Eighties and Nineties.
The research, by scientists at McGill University in Montreal, suggests that "trippy" experiences can be brought on by the expectation you are about to get high.
To test whether psychedelic effects could be induced by a placebo, Canadian researchers gave 33 volunteers – who believed they were taking part in a study of the effects of drugs on creativity – the fake LSD at a four-hour psychedelic party with DJ, colourful paintings and light show.
To convince participants they had been given a hallucinogenic, there were ten white-coated staff, a security guard and several actors who behaved as though they had taken a psychedelic substance.
When asked near the end of the study, 61 percent of the volunteers reported some effect of the drug, ranging from mild changes to symptoms resembling taking a moderate or high dose of an actual drug.
Several of the volunteers said they saw paintings on the walls "move" or "reshape" themselves. Others described themselves as feeling "heavy... as if gravity [had] a stronger hold", and one described having a "come down" before another "wave" hit her.
Several were certain that they had taken a psychedelic drug.
Samuel Veissiere, a cognitive anthropologist who teaches at McGill’s Department of Psychiatry and supervised the study, said: "These results may help explain 'contact highs' in which people experience the effects of a drug simply by being around others who have consumed it.
"More generally, our study helps shed light on the 'placebo boosting' component inherent in all medical and therapeutic intervention, and the social influences that modulate these enhancing effects."