A pilot study suggests that low doses of LSD may have different effects on sustained attention in women and men. The findings, presented at the ECNP annual congress in Munich, are preliminary, but they add to growing evidence that people may not all respond to psychedelic microdosing in the same way.
Microdosing means taking a very small amount of a psychedelic drug, below the level usually associated with a full psychedelic experience. Some people report using low-dose LSD in the hope of improving focus, concentration, productivity or mood, and there are also anecdotal reports of people using it to manage problems with attention. However, controlled scientific studies have produced mixed results, making it important to test these claims carefully.
A group of researchers from the University of Maastricht tested the responses of volunteers to microdosing. The randomised controlled study involved 48 healthy volunteers, including 24 women, with an average age of 36.9 years. Participants were randomly assigned to receive either placebo or four low doses of LSD, each containing 15 micrograms, over a two-week period (typical psychedelic effects tend to appear with doses greater than 60mcg). Neither the participants nor the researchers knew who had received LSD and who had received placebo until after the study was completed.
Researchers looked at three areas of mental performance: sustained attention, information processing and working memory. Participants completed tests at the start of the study, after the first dose, after the fourth dose and at follow-up. The most notable result was seen in a test of sustained attention, where people had to watch a screen and respond as quickly as possible when a signal appeared.
Women given the placebo in the study tended to have slower reaction times and more attention lapses than men given the same task. Under low-dose LSD, however, women responded about 8% faster to the stimulus than in the placebo condition (335ms, compared to 308ms under LSD) and made on average 2.3 sustained attention lapses, as against the 4.7 lapses made by the women who received the placebo. For attentional lapses, this pattern was seen after the first dose, after repeated dosing and at follow-up. No comparable improvement was observed in men given the microdoses.
Lead researcher, Iva Totomanova (of the University of Maastricht) said:
"We examined the effect of LSD on 3 different cognitive tasks. The key finding was that LSD improves how women can sustain attention in certain tasks. With the information processing and working memory cognitive tasks, the results were not as clear-cut, which may have led sex-related effects being missed in previous studies. It's important to note that while our work suggests that microdosed LSD improves sustained attention in women, it does not show that low-dose LSD generally improves cognition, nor that women are generally more responsive to LSD than men. Instead, the results point to a more cautious message: effects may depend on the person, the cognitive task being measured and the circumstances of use. A better question may be, who responds to microdosing, and under what circumstances?"
The work is a re-analysis of an earlier completed study, so the authors say the results need to be confirmed in research designed specifically to examine sex differences (for example, by looking at hormone concentrations in the blood and taking into account menstrual phase, contraceptive use, etc).
Ms Totomanova added "This is a small pilot study, so it does need to be confirmed in a larger population. If we can do that it may help us understand why some people respond to LSD in a particular way, when others don't. We are beginning to see that people respond to psychedelics in different ways. With psychedelic pharmaceuticals, it looks like personalised medicine is important".
Commenting, Dr Mikkel Højlund (of the University of Southern Denmark) said:
"Microdosing of psychedelics has received much attention in media, so testing this in a proper research context is important to advance our knowledge on the subject. Even though it is a double-blind placebo-controlled study, the researchers are cautious: as they say, this is a small study, with several variables, but it merits further work on a bigger scale".
This is an independent comment, Dr Højlund was not involved in this work.
