A national survey suggests use of synthetic drugs increased from 2009 to 2013. Many people who use these drugs also use other illicit drugs such as LSD, cocaine and Ecstasy, according to the researchers from NYU Langone Medical Center.

The survey included data from the National Survey of Drug Use and Health on drug use among young people ages 12 to 34. Use of synthetic drugs was most common among males, whites, people with lower incomes and city dwellers, News-Medical.net reports. The survey looked at self-reported use of 57 new drugs. About 1 percent of respondents said they used any of the new drugs.

The findings are published in Drug and Alcohol Dependence.

“This is the first study reporting on use of a variety of new drugs in a nationally representative U.S. sample,” lead researcher Joseph J. Palamar, PhD, MPH, said in a news release. “However, we’re pretty confident that use of new drugs was severely underreported, as the research subjects were not asked about most of these drugs specifically.”

He said previous research suggests use of bath salts and synthetic marijuana are much higher than this survey indicates. “Hundreds of new psychoactive drugs have come out in recent years and some of them can be very dangerous,” he said. “We need health surveys to ask about use of new drugs, in addition to traditional drugs such as marijuana and cocaine, in order to quickly pick up on potential drug epidemics.”