Synthetic marijuana known as Spice can cause long-lasting psychosis, according to a report at the American Psychiatric Association Annual Meeting. Doctors at the Naval Medical Center in San Diego reported that in 10 men hospitalized for psychosis caused by Spice, symptoms lasted for days or even months.

The Los Angeles Times reports that synthetic marijuana, also known as K2, Blaze or Red X Dawn, consists of plant material covered with synthetic chemicals designed to produce a high similar to that caused by marijuana. The compounds have not been approved by the U.S. Food and Drug Administration and little is known about their safety, according to the American Psychiatric Association.

In the 10 men described in the study, symptoms from Spice included paranoid delusions, hallucinations and suicidal thoughts. While most of the men recovered in five to eight days, some had symptoms for as long as three months.

Synthetic drugs are a growing problem in the military. The drugs are increasingly being abused by military members who are trying to pass traditional drug tests. All four branches of the military have banned the use of synthetic drugs.