People who drink at least seven drinks a week could be at an increased risk of abusing amphetamines compared with those who drink less alcohol, according to a new study.

The finding adds to mounting evidence that suggests even moderate drinkers could be more susceptible to the addictive effects of stimulants, the researchers said.

"Lots of us sample drugs at some point in our college careers , but most of us don't go on to abuse them," said study researcher Craig Rush, a professor of behavioral science, psychiatry and psychology at the University of Kentucky.

The goal of the study was to learn why some people become drug abusers, Rush said.

The four-year study began in 2005, with 33 volunteers, ages 21 to 30, recruited from Lexington and around the university. The 16 women and 17 men underwent a series of medical exams including cardiovascular tests, and reported their drug histories.

After the tests, the researchers evaluated the participants based on their alcohol intake, and split them into groups of light drinkers (those that had up to six drinks a week) and moderate drinkers (those that had seven to 14 drinks a week).

The researchers gave all participants eight capsules containing either a low-dose (8 to 10 milligram) amphetamine, a high-dose (16 to 20 mg) amphetamine or a placebo. The researchers then gave the participants opportunities to earn more of the stimulant one-eighth of their first dose by working on a computer exercise.

Researchers found that moderate drinkers worked more for high-dose amphetamines and reported feeling greater effects of the drug than light drinkers.

They also found that, compared to the placebo, both doses of amphetamines increased the likelihood the moderate drinkers would work for more drugs. Only the high dose had this effect in light drinkers.

"Hopefully, what this should result in is educating college-age students about the hazards of drinking beyond drinking and driving ," Rush told MyHealthNewsDaily. "Going out and drinking seven-plus drinks a week can have consequences in terms of other drug use."

The results are consistent with a 2003 study published in the journal Alcoholism: Clinical & Experimental Research, which found that moderate alcohol use may raise susceptibility to drug abuse, the researchers said.

Further studies will examine how moderate drinkers react to other drugs, such as opiates and sedatives, Rush said.

While some previous studies suggest the use of amphetamines in treating addictions to drugs such as cocaine, Rush said, any such treatment is likely to alter an addict's behavior.

"There is no magic bullet out there that we are going to find that's just going to stop people from using [drugs]," he said. "There's a lot of behavior involved with drug use and abuse . We've got to deal with that as well."

In 2009, approximately 7 million Americans ages 12 and older used psychotherapeutic drugs for non-medical reasons, according to the 2009 National Survey on Drug Use and Health.

The study will be published in the March 2011 issue of the journal Alcoholism: Clinical & Experimental Research.