In a recent survey of 368 active-duty Army personnel, 38 percent of those who admitted using any drug in the last 90 days said they used synthetic marijuana instead of traditional marijuana (14 percent).

Synthetic cannabis, also called "K2" or "spice," is the drug most used by soldiers. This is probably due to the difficulty in testing for the marijuana-like substance.

Soldiers believe that they use synthetic marijuana more than those who aren't in the military.

"For every category of drug that we listed, soldiers believed that civilians use more drugs than soldiers. However, for spice, or synthetic cannabis, soldiers believed folks in the military use more than civilians," said study researcher Tom Walton, a project director at the School of Social Work at the University of Washington in Seattle. 

If a soldier is caught abusing a substance, they often face serious consequences, including automatic termination. In turn, soldiers avoid most illegal drugs. But spice and K2 are hard to test for, and soldiers often face great levels of stress. Thus, they turn to synthetic marijuana to cope.

Synthetic marijuana is so hard to test for is because of its constantly changing chemical formula and the many different varities of the substance available. Drug tests seek to find users positive with certain banned substances. In response, synthetic marijuana makers alter its makeup to get rid of those substances so users don't fail drug tests.

The military plans to add synthetic marijuana to its urine analysis tests but are unsure when, or how to do this. They already banned the substance in 2012.

Synthetic marijuana does have side effects. These range from nausea and seizures to paranoia and anxiety. Some soldiers, however, apparently disregard those side effects knowing that they're still getting a high experience and likely won't get caught doing it.