Feeling a little less sharp today? A drug approved by the FDA to treat sleep disorders such as narcolepsy, is being used off-license as a "smart drug" to enhance cognitive performance.

Previous studies show that modafinil (Provigil) can improve alertness and concentration in people who are sleep-deprived, but less emphasis has been placed on its effect on those who are not sleep-deprived but simply want a brain-boost.

Now, a new review published in the journal European Neuropsychopharmacology shows that modafinil also gives significant cognitive benefits to those who are not sleep-deprived.

Dr. Ruairidh Battleday and Dr. Anna-Katharine Brem from the University of Oxford and Harvard Medical School evaluated all research papers about using modafinil for cognitive enhancement. They found 24 studies dealing with different benefits associated with taking the drug, including planning and decision making, flexibility, learning and memory, and creativity.

The found that the benefits of modafinil varied according to the activity, and that the longer and more complex the task, the more benefits the drug bestowed.

While modafinil made no difference to working memory, or flexibility of thought, the review showed it improved higher brain functions, such as the ability to understand new material and make decisions based on it, verifying its reputation as a "smart drug."

"The authors say that modafinil may well deserve the title of the first well-validated pharmaceutical nootropic agent," said Professor Guy Goodwin, President of the European College of Neuropsychopharmacology. "In other words, it's the first real example of a 'smart drug', which can genuinely help, for example, with exam preparation."

The validation brings up ethical questions, such as whether students should be allowed to have an advantage over others by taking the drug.