"Robotripping" -- getting high on cold medicine -- appears to be back in vogue with U.S. teens.

Although cough syrup abuse has been around for more than 30 years, cases of teens overdosing on Robitussin, NyQuil, Benadryl and Coricidin seem to be increasing in frequency, addiction expert Dr. Drew Pinsky told ABC's Good Morning America.

The culprit ingredient in these over-the-counter medications is dextromethorphan, a common additive in cough suppressants that can cause hallucinations when taken in large quantities, Pinsky said.

Users can suffer psychosis, brain damage, and seizures. Last year, 14 people died from deliberate overdoses of cold medicine, according to Pinsky, and several hundred were hospitalized.

This news comes at the same time as a University of Michigan study that reports a downward trend in drug, alcohol, and tobacco use among American teenagers.