The number of emergency department visits involving the drug ecstasy more than doubled from 2005 to 2011, according to data from the Substance Abuse and Mental Health Services Administration.

Over the 6-year window, young adults and adolescents presenting at emergency departments after using 3,4-methylenedioxy-methamphetamine -- known as MDMA, ecstasy in pill form, and Molly in powder form -- rose from 4,460 admissions in 2005 to 10,176 in 2011, roughly a third of which also involved alcohol, the agency published on its website.

They cautioned that use of the drug -- which has stimulant and hallucinogenic properties -- in concert with alcohol can enhance its effects "and may increase risk of abuse."

A small study on heavy MDMA use has shown that use of roughly 40 pills a year was associated with hippocampal shrinkage, which may have adverse outcomes on memory.

MDMA has also been associated with elevated body temperatures, high blood pressure, heart failure, kidney failure, anxiety, and confusion. Heart rate and blood pressure effects are likely due to the drug triggering the release of norepinephrine.

"Ecstasy is a street drug that can include other substances that can render it even more potentially harmful," noted Peter Delany, PhD, Director of SAMHSA's Center for Behavioral Health Statistics and Quality, in a statement.

Data from the National Institute on Drug Abuse (NIDA) has found ecstasy cut with methamphetamine, caffeine, dextromethorphan, ephedrine, and cocaine, which users may not be aware of at the time of use and may be consumed with other substances, such as alcohol.

Fatalities related to MDMA use made headlines in late August 2013, when two young adult attendees of the electronic music festival Electric Zoo in New York City, N.Y., died, one of whom suffered a massive seizure after ingesting a reported "six hits of Molly," according to the New York Post.

However, hundreds of thousands of people use the drug -- the NIDA data suggests around 450,000 U.S. citizens were current users of the drug in a 2004 survey -- but deaths directly related to use are uncommon. A BBC report on drug use found roughly 500,000 English citizens use MDMA annually, but use was associated with 27 deaths.