LSD-assisted therapy could provide benefits to patients struggling with anxiety disorders, according to new research published in Biological Psychiatry. The findings suggest that the psychedelic drug can produce notable reductions of anxiety and comorbid depression symptoms.

LSD-assisted therapy involves the controlled administration of lysergic acid diethylamide under the guidance of a trained therapist. Although LSD is best known as a recreational drug, some research suggests that it can have powerful therapeutic effects in a wide range of psychiatric conditions when combined with psychotherapy.

The findings from the new research provide preliminary evidence that LSD-assisted therapy can result in long-term reductions in anxiety symptoms. “The response was surprisingly sustained,” said study author Matthias Liechti, a professor of clinical pharmacology at University Hospital Basel.

A small pilot study had already found evidence that LSD-assisted therapy could help reduce anxiety symptoms in patients with life-threatening illness. The new double-blind, placebo-controlled study sought to corroborate these findings in patients with anxiety with and also without a life-threatening illness.

“Primarily, we wanted to confirm a pilot study on the effects of LSD in patients with anxiety and life-threatening illness,” Liechti explained. “Secondly, we also wanted to explore therapeutic benefits in patients with an anxiety disorder such as general anxiety disorder and without the somatic illness. Furthermore, we wanted to use LSD instead of psilocybin, which is more commonly used in modern psychedelic research, to broaden the field.”

The study included 20 participants who had a life-threatening somatic illness (such as a diagnosis of cancer) and 22 participants with an anxiety disorder that was not associated with a somatic illness. Psychiatric symptoms were assessed with the Spielberger’s State-Trait Anxiety Inventory, the Hamilton Depression scale, the Beck Depression Inventory, and the Symptom-Check-List-90-R — scientifically-validated questionnaires that are widely used both in clinical settings and in research.

Each participant underwent an initial screening visit and two 24-week treatment periods. The study employed a crossover design, meaning that the participants were randomly assigned to receive either LSD or placebo in the first treatment period and vice versa in the second treatment period. The participants 200 μg of LSD, a relatively high dose.

The researchers found that LSD produced strong reductions in anxiety, depression, and general psychiatric symptomatology compared with placebo. These reductions were still observed 16 weeks after the last LSD treatment.

“LSD may have therapeutic benefits in anxiety disorders and also reduce depression,” Liechti told PsyPost. “The therapeutic effects set in fast and were sustained up to 16 weeks following the treatment with two single doses of LSD.”

The researchers also found evidence that some of the specific subjective effects of LSD were linked to reductions in anxiety. In particular, participants who reported greater feelings of oceanic boundlessness, which is characterized by a feeling of oneness with the world, were more likely to experience long-term reductions in anxiety symptoms. The same was true for participants who scored high on a measure of mystical experiences.

“LSD was overall well tolerated,” Liechti noted. During the entire study, a total of nine serious adverse events occurred. Six of these events occurred during the LSD treatment period.

But only one serious adverse event was considered related to treatment, according to the researchers. A patient experiencing anxiety and delusions during an LSD session was treated with lorazepam and olanzapine. “The patient was kept overnight and discharged in the morning and experienced no further long-term symptoms.”

While the initial results are promising, Liechti said that “more studies are needed to confirm these effects.” The issue of unblinding has been raised as a concern for psychedelic research. Because of the powerful subjective effects of LSD, it’s easy for participants to determine whether they’ve received the substance or a placebo.

“The blinding of the acute effects of psychedelics is not possible against a placebo,” Liechti said. “Future studies may therefore include different doses and show a dose-response effect instead.”

The study, “Lysergic acid diethylamide-assisted therapy in patients with anxiety with and without a life-threatening illness: A randomized, double-blind, placebo-controlled Phase II study“, was authored by Friederike Holze, Peter Gasser, Felix Müller, Patrick C. Dolder, and Matthias E. Liechti.