The San Diego Naval Medical Center says it admitted 15 sailors over a five-month period last year for use of a synthetic drug that mimics marijuana.
Doctors say side effects of the drug often known as Spice include hallucinations, paranoia and confusion that can become debilitating. The symptoms can often last days.
The San Diego Union-Tribune said Tuesday the Navy spent the past year battling the new designer drug, which at first was legal and couldn't be detected by commonly used drug tests.
The U.S. Drug Enforcement Administration named the drug a controlled substance on March 1 in an emergency action, making it illegal for over-the-counter sales.
In January, seven students were discharged from the U.S. Naval Academy due to use of the drug.