CAMBRIDGE, United Kingdom — So-called “smart” drugs, commonly used by students, might actually impair cognitive function, according to a new study. Researchers in the United Kingdom say drugs such as Ritalin, a common prescription medication for individuals with ADHD to enhance their concentration and cognitive performance, are often abused by students without the disorder.

In a series of four double-blind, randomized trials spaced a week apart, 40 healthy participants took either a placebo or one of three popular “smart” ADHD drugs. These included methylphenidate (sold as Ritalin), modafinil (Provigil), and dextroamphetamine (Adderall).

The team evaluated participants based on their performance in a test designed to simulate the complex decision-making and problem-solving tasks encountered in everyday life. They had to complete an exercise known as the Knapsack Optimization Problem, or “knapsack task.” In this task, the group received a virtual backpack and a selection of items with varying weights and values. They had to determine how to allocate the items in the backpack to maximize the total value of its contents.

Participants who took the ADHD drugs experienced small reductions in accuracy and efficiency, along with significant increases in time and effort, compared to their results when not on the drugs. While taking Ritalin, for example, participants took approximately 50 percent longer on average to complete the task than when they consumed a placebo.

“Our results suggest that these drugs don’t actually make you ‘smarter. Because of the dopamine the drugs induce, we expected to see increased motivation, and they do motivate one to try harder. However, we discovered that this exertion caused more erratic thinking — in ways that we could make precise because the knapsack task had been widely studied in computer science,” says Professor Peter Bossaerts, a professor of neuroeconomics at the University of Cambridge, in a media release. “Performance did not generally increase, so questions remain about how the drugs are affecting people’s minds and their decision making.”

Additionally, participants who performed well with the placebo often showed a more significant decline in performance and productivity after taking an ADHD drug. Those who ranked in the top 25 percent with a placebo frequently fell into the bottom 25 percent when under the influence of Ritalin.

Conversely, those who performed poorly with the placebo only occasionally showed minor improvements after taking a drug.

“Our research indicates that drugs anticipated to improve cognitive performance in patients may, in fact, cause healthy users to work harder while producing lower quality work over an extended period,” adds study author Dr. Elizabeth Bowman, a researcher at the Centre for Brain, Mind, and Markets at the University of Melbourne.

The study is published in the journal Science Advances.

You might also be interested in:

• As many as 1 in 4 middle and high schoolers abuse ADHD drugs Adderall, Ritalin
• Microbes causing a ‘leaky gut’ may be triggering ADHD in children
• Want better grades in college? Getting more sleep may boost your GPA

South West News Service writer Alice Clifford contributed to this report.