The big picture of stimulant abuse has continued to shift over the past few years, a new study published Tuesday in The Journal of Clinical Psychiatry finds.

The authors analyzed six years worth of data (2005 to 2011) from three national surveys in order to figure out how adults and teens are using adderall (the brand name for dextroamphetamine-amphetamine) and ritalin (methylphenidate), two of the most commonly prescribed stimulants on the market. They found that the nonmedical use of ritalin dropped by 54 percent in that time period, while rates of adderall misuse stayed stable, as did the amount of emergency room visits related to either drug. Once the researchers took a closer look, however, they came upon a disturbing trend: In adults specifically, the rate of adderall misuse jumped by 67 percent and there was an 156 percent increase in the number of emergency room visits. No such disparities existed for adult ritalin users.

"The growing problem is among young adults," said study co-author Dr. Ramin Mojtabai, a professor of mental health at the Johns Hopkins Bloomberg School of Public Health, in a statement. "In college, especially, these drugs are used as study-aid medication to help students stay up all night and cram. Our sense is that a sizeable proportion of those who use them believe these medications make them smarter and more capable of studying. We need to educate this group that there could be serious adverse effects from taking these drugs and we don't know much at all about their long-term health effects."

That sense is further beared out by the team’s finding that out of all adderall misuse among people 12 years or older, 60 percent was reported by adults ages 18 to 25. At the same time, ER visits among teens ages 12 to 17 decreased by 53 percent from 2005 to 2011, as did treatment visits in general. According to a 2013 report from the Drug Abuse Warning Network, there were 15,585 ER visits related to the nonmedical use of prescription stimulants in 2010, a three-fold increase from 2005. Like the current study, the report found ER visits only increased among adults 18 or older during that time period.

Interestingly enough, the rise in adult adderall abuse largely isn’t the result of overprescription. "The number of prescriptions for Adderall has fallen and yet we are seeing more medical problems from its use," explained lead author Dr. Lian-Yu Chen. "This suggests that the main driver of misuse and emergency room visits related to the drug is the result of diversion, people taking medication that is legitimately prescribed to someone else. Physicians need to be much more aware of what is happening and take steps to prevent it from continuing."

Among all age groups and for both drugs, the primary nonmedical source was from friends and relatives; two-thirds of these individuals had in turn received their drugs from a legitimate physician.

While adderall is plenty useful for improving focus, particularly for individuals with attention deficit/hyperactivity disorder, Mojtabai believes people are often blind to its potential adverse effects, which can include insomnia, dependence, and the risk of sudden cardiac death. In 2006, the FDA affixed a black box label warning to adderall specifically warning of these risks and more.

"Many of these college students think stimulants like Adderall are harmless study aids," he said. "But there can be serious health risks and they need to be more aware."

Source: Chen L-Y, Crum R, Strain E, et al. Prescriptions, Nonmedical Use, and Emergency Department Visits Involving Prescription Stimulants. The Journal of Clinical Psychiatry. 2016.