Tens, perhaps hundreds of thousands of Afghanistan and Iraq war veterans suffer from post-traumatic stress disorder (PTSD). So do millions of other Americans. The Department of Veterans Affairs estimates that more than 5 million people suffer from PTSD in a given year.

New clinical research suggests there is something that can help: Marijuana. Yep, you read that right. The Journal of Psychoactive Drugs this week published results from a New Mexico study that found patients reported an average 75% reduction in all three areas of PTSD symptoms while using marijuana.

Patients in the study all met the diagnostic criteria for PTSD and were symptomatic. When they used marijuana, they reported significant relief from PTSD symptoms, as well as a lack of harm or problems functioning because of marijuana use. The study used a standard PTSD evaluation tool to rate the frequency and intensity of symptoms.

"Many PTSD patients report symptom reduction with cannabis, and a clinical trial needs to be done to see what proportion and what kind of PTSD patients benefit, with either cannabis or the main active ingredients of cannabis," said George Greer, one of the researchers.

The study used smoked marijuana and was done with patients in New Mexico, which in 2009 became the first state to authorize the use of medical marijuana for PTSD. Since then, six other medical marijuana states have approved it. And in the four legal marijuana states and the District of Columbia, any adult can use marijuana for any reason.