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Using stimulant drugs like cocaine, amphetamines and ADD/ADHD drugs even occasionally can permanent dull the brain, according to researchers.

Researchers at the University of California, San Diego School of Medicine said brain scans of college students who used stimulant drugs showed impaired neuronal activity in regions associated with anticipatory functioning.

The latest study, which used functional magnetic resonance imaging, suggests that brain changes from occasional use of stimulant drugs can make people more prone to drug addiction later in life.  Researchers define occasional users as those who have taken stimulants for an average of 12 to 15 times.

"If you show me 100 college students and tell me which ones have taken stimulants a dozen times, I can tell you those students' brains are different," Dr. Martin Paulus, professor of psychiatry at UC San Diego said in a news release. "Our study is telling us, it's not 'this is your brain on drugs,' it's 'this is the brain that does drugs.'"

Participants in the latest study were college students aged 18 to 24. They were shown either an X or an O on a screen and told to press, as quickly as possible, a left button if an X appeared or a right button if an O appeared. Participants were instructed not to press a button if they here a tone. Researchers recorded participants' reaction times and errors.

After accounting for other factors like alcohol dependency and mental health disorders, researchers found that occasional users have slightly faster reaction times, suggesting a tendency toward impulsivity. Researchers found that the difference between occasional drug users and non-users was most pronounced during the "stop" trials. The study revealed that occasional users made significantly more mistakes compared to the control group. Their performance also worsened as the task became harder.

Further analysis revealed that brain scans of occasional users showed consistent patterns of less neuronal activity in the parts of the brain associated with anticipatory functioning and updating anticipation.

"We used to think that drug addicts just did not hold themselves back but this work suggests that the root of this is an impaired ability to anticipate a situation and to detect trends in when they need to stop," lead author Katia Harlé, PhD, a postdoctoral researcher in the Paulus laboratory said in a news release.

"Right now there are no treatments for stimulant addiction and the relapse rate is upward of 50 percent," Paulus added. "Early intervention is our best option."

The findings are published in the Journal of Neuroscience.