Sept. 4 (UPI) -- A study of a pharmaceutical form of the psychedelic drug lysergic acid diethylamide suggests it might relieve anxiety symptoms for up to three months.

The results of a preliminary study on the effects of MM120, which is an oral form of LSD, show that a single dose could lessen the symptoms of generalized anxiety disorder, according a study published on Thursday in the Journal of the American Medical Association, USA Today reported.

Researchers at New York-based biotech company MindMed conducted the study on 198 adults who were diagnosed with generalized anxiety disorder.

"Ours is the first modern trial to look specifically at LSD, or any psychedelic, for generalized anxiety disorder," MindMed's Dan Karlin told New Scientist.

The disorder causes excessive worry regarding a wide variety of things, including relationships and employment, and often is treated with anti-depressants, mood-enhancing drugs and talk therapy.

Selective serotonin reuptake inhibitors often are prescribed to treat the condition but don't work for about half of patients, Karlin said.

They also can have unwanted side effects, such as suppressing emotions, and only work when taken on a daily basis.

Prior studies have shown LSD might be an effective alternative medication that increases the amount of the brain's mood-enhancing serotonin.

The MindMed study indicated nearly two-thirds of adults who took a single dose of MM120 had improved anxiety symptoms 12 weeks later, versus about 31% of those who took a placebo.

The study also showed a remission rate of nearly 48% after 12 weeks, versus 20% for those who took a placebo.

LSD has been a popular, but illegal, recreational drug since at least the 1960s due to its mood-enhancing capabilities and potential for inducing hallucinations.

About 90% of study participants given LSD experienced hallucinations after taking a 100mg dose.

Other reported side effects include nausea and headaches.

"It's a very impressive study," Harriet De Wit, a professor at the University of Chicago's Department of Psychiatry and Behavioral Neuroscience, told ABC News.

"The investigators are experts at clinical trial design," she added, "and I was very struck by the results."

MindMed has launched additional clinical trials in the United States and Europe and might seek approval from the Food and Drug Administration to market the drug as an anxiety treatment.