LSD boosts people’s suggestibility, raising possibility of clinical uses

A rigorously controlled new study reports that a dose of LSD makes us more susceptible to suggestions, a finding that raises the possibility of clinical usage in contexts where hypnosis has proven effective.

The study recruited 10 participants (9 men), aged 27–47, all of whom had used psychedelics in the past, but were clear of any diagnosis of mental illness. They attended two testing sessions 5–10 days apart where placebo was administered in the first session, and a standard dose of LSD (40–80 μg) on the second. This fixed order was necessary to avoid any leakage of psychedelic effects from one session to another, mimicking the design of an earlier experiment on nitrous oxide.

Two hours after receiving placebo/dose, participants closed their eyes and were led through a series of standard suggestions used in hypnosis research, such as imagining hearing exquisite music, feeling time slowing, or their finger becoming numb. Their subsequent ratings of vividness of the imaginings were nearly one point higher (on a five-point scale) in the LSD session than the placebo, a significant effect.

LSD led to bigger rises in suggestibility for participants who scored higher on a measure of conscientiousness. Conscientiousness is associated with "ego control", and it may be that LSD's much-reported effect of "ego dissolution" may be pulling down bulwarks that would otherwise make these individuals resistant to accepting suggestions.

If you've had personal experience with LSD, the results of this study may seem plausible to you. If you haven't, users report a sense of the external world mingling with their own thoughts. Also, groups of people who "go on a trip" together tend to converge on the same ideas and feelings in an uncanny fashion. Given these subjective accounts it makes sense that the drug was associated with increased suggestibility in this research. The practical significance of this finding is that it shows the malleability offered by LSD has parallels with how hypnosis operates, justifying and paving the way for exploration of LSD in contexts where hypnosis has proven effective – clinically in areas such as pain, PTSD and weight loss, often in conjunction with other interventions.

It's high time for LSD to receive this renewed focus. Its potential for suggestibility was investigated clinically – albeit without the placebo controls we see here – way back in the 1950s (and no doubt influenced its investigation in the CIA's infamous MK-Ultra programme for mind control). Indeed, in its early days LSD was considered full of promise for clinical applications; a meta-analysis of a set of trials looking at LSD treatment for alcoholism showed an effect that hasn't been bettered by any other means.

Regulatory restrictions imposed in the mid–1960s slammed shut the door onto these perceptions, forcing later researchers to operate in an unwelcoming climate, including political obstacles and costly, difficult licensing criteria, which explains why peer-reviewed articles gave way to albums and other missives of the counterculture as our main sources of information about the significance of hallucinogens.

Now we may be seeing the beginning of a renaissance of psychedelic research, with fuller understanding of its activity at the levels of neuronal populations and brain regions, and clinical investigation into its use to reduce anxiety in those with terminal illness.

Further reading

R. L. Carhart-Harris & M. Kaelen & M. G. Whalley & 7 M. Bolstridge & A. Feilding & D. J. Nutt. (2014). LSD enhances suggestibility in healthy volunteers. Psychopharmacology.