Low doses of the psychedelic drug LSD increase complexity in the brain, even when they donāt alter a personās consciousness. The finding challenges the idea that these two phenomena are correlated and raises the possibility that even small doses of LSD might have therapeutic effects.
Neural complexity is a measure of the amount of information the brain produces, with all repetitive signals removed ā that is, the lowest number of unique brain signals over a given period. Previous studies have shown neural complexity correlates with consciousness. So, it decreases when people are asleep or in a coma and increases when they are awake. High doses of psychedelic drugs also boost neural complexity, leading some experts to posit that this may be how the drugs exert their therapeutic effects.
But it has been unclear if neural complexity changes with small doses of psychedelics. To tackle this question, at the University of California, Los Angeles, and his colleagues gave 21 adults either a placebo or one of two microdoses of LSD ā 13 or 26 micrograms. LSD doses this small typically donāt elicit hallucinatory effects.
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The researchers assessed neural complexity by measuring the electrical activity of each participantās brain using electroencephalography (EEG). Participants also completed a questionnaire afterwards to determine whether they had experienced an altered state of consciousness.
The team repeated these experiments in two additional groups using high doses of tetrahydrocannabinol, or THC ā a psychoactive compound in marijuana ā and methamphetamine. At high doses, THC, but not methamphetamine, can influence consciousness.
Of all the drugs, only the 26-microgram dose of LSD significantly changed neural complexity. Compared with the placebo, this LSD dose raised complexity by about 12 per cent, on average. The questionnaire also indicated the 26-microgram dose didnāt alter consciousness, although participants reported feeling some effects from the drug. Murray says this challenges the previous notion that shifts in complexity and consciousness are always correlated, a finding further supported by the fact that THC altered participantsā consciousness without changing their neural complexity.
āAs some of the earlier papers weāve published with these [LSD] doses have shown, they act on the brain in [similar] ways [to] some of the higher doses,ā says Murray. That may be why people report feeling more creative and connected with others when microdosing LSD. However, clinical trials havenāt found that microdosing improves overall well-being more than a placebo, making it unclear if these small doses are really beneficial, especially given potential risks. āWe really donāt know the dangers of repeated low doses, either on the brain or other organs,ā says Murray.
Taking psychedelics has previously been shown to increase the brainās overall entropy, but this new result shows that the effect is dependent on the dosage, says at the University of California, San Franscisco. āIt suggests that [neural complexity] is not a mere arousal effect, as it didnāt increase with methamphetamine, nor a generic āhighā, as it didnāt increase with THC,ā he says.
However, he disagrees with the researchers claim that low doses of LSD donāt influence consciousness since participants reported feeling the drug. āI think we need better scales to pick up on psychedelic effects,ā he says.
Neuropsychopharmacology
