LSD has been used in a controlled clinical trial approved by the U.S. Food and Drug Administration for the first time in more than 40 years, according to The LA Times. The psychoactive drug was used in combination with therapy to study the anti-anxiety effects on on patients facing life-threatening illnesses, where were considerable and constant, as well as free from troubling side effects.
According to the report, "12 patients suffering deep anxiety due to serious illnesses participated in several drug-free psychotherapy sessions, and then joined a pair of therapists for two full-day psychotherapy sessions, separated by two to three weeks, under the influence of LSD."
Patients were either given a placebo, a small dose, or full dose of LSD, and those who received the full dose "experienced measurable and lasting improvements in their 'state' and “trait” anxiety scores," far beyond those who received either the placebo or small dose.
In the '60s, LSD-aided psychotherapy was widely practiced in the US until 1966, but became illegal with the increase of recreational use, ending all US research on the drug's possible benefits on mental health.
MDMA has also been the subject of clinical trials regarding mental health, recently, specifically for patients suffering from post traumatic stress disorder.