Dr. Ahmed Dahir Mohamed, at the University of Nottingham Malaysia Campus, who helped find that the drug Modafinil may not make healthy people perform better on cognitive tests.

It's reported that 1 in 5 students take the drug Modafinil in hopes of boosting their academic performance, but this so-called "smart drug" may actually impair their ability to answer questions quickly and correctly, a new study finds.

The drug, also known by the brand name Provigil, is approved the U.S. Food and Drug Administration to help people with narcolepsy and other sleep disorders stay awake. But healthy people account for about 90 percent of Modafinil's use; they take the drug because they believe it might increase their attention and wakefulness, the researchers said.

Now, a new study finds that Modafinil does not turn healthy people into A-plus students. [10 Facts Every Parent Should Know About Their Teen's Brain]

"We looked at how the drug acted when you are required to respond accurately and in a timely manner," co-author of the study Ahmed Dahir Mohamed, of the School of Psychology at the University of Nottingham Malaysia Campus, said in a statement. "Our findings were completely opposite to the results we expected."

The scientists gave 32 people the drug and another 32 people a placebo. The research was a randomized double-blind study, so neither the participants nor the researchers knew who received the active drug.

All of the study participants completed a well-known neuropsychological task, called the Hayling Sentence Completion Test, which requires participants to finish a sentence and fill in missing words as quickly and accurately as possible.

On average, the people who took Modafinil had slower reaction times and an impaired ability to complete the sentences in a timely manner, compared with those who took the placebo, according to the study published Nov. 12 in the journal PLOS ONE.

Moreover, people in the two groups made a similar number of errors on the task, indicating that Modafinil does not improve task performance, the researchers found.

"It has been argued that Modafinil might improve your performance by delaying your ability to respond," Mohamed said. "It has been suggested this 'delay-dependent improvement' might improve cognitive performance by making people less impulsive. We found no evidence to support those claims."

He added, "Our research showed that when a task required instant reactions, the drug just increased reaction times, with no improvement to cognitive performance."

The new finding echoes those of other studies, which have found that Modafinil may not improve spatial working memory, logic memory, verbal fluency, attention shifting, spatial planning or sustained attention in healthy volunteers.

Modafinil may also impair people's abilities to respond to questions in creative ways, according to a study that Mohamed and his colleagues published in September in The Journal of Creative Behavior.

But the drug did benefit some people. When the researchers examined participants' abilities to creatively solve a problem, results showed that people who were not creative to start with improved after taking Modafinil.

"Our study backs up previous research that suggests psychostimulants improve people at the lower end of the spectrum in cognition, whereas they impair people who are at the optimum level of cognitive function — healthy people for example," Mohamed said.

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