Ever since the federal government began passing a series of laws that made marijuana illegal in the first half of the 20^th century, one of the big arguments opponents make revolves around cannabis severely inhibiting brain function.

A new study finds that may not be the case with medical marijuana. Furthermore, the reverse might actually be true.

In a recently released report, researchers at McClean Hospital in Belmont, Mass., focused on the impact of medical marijuana on executive functions. These include areas such as cognitive flexibility, memory, Inhibition control and ability to focus attention.

Researchers found a result that opposes the long-held conventional wisdom on marijuana.

“After three months of medical marijuana treatment, patients actually performed better, in terms of their ability to perform certain cognitive tasks, specifically those mediated by the frontal cortex,” Dr. Staci Gruber,. director of the hospital’s Marijuana Investigations for Neuroscientific Discovery, said in a statement.

How The Cognitive Performance Study Worked

Gruber’s group published the study’s findings in the journal, “Frontiers In Pharmacology” under the title, “Splendor in the Grass: A Pilot Study Assessing the Impact of Marijuana on Executive Function.”

According to McClean Hospital, an affiliate of the Harvard School of Medicine, the study is believed to be the first to examine the impact of medical marijuana on cognitive functions. Researchers selected a test group which had not used marijuana in at least the last 10 years and tested their cognitive skills. They then were tested again after three, six and 12 months of medical marijuana use.

In addition to higher scores on executive functions, those who participated in the study reported improvement in their medical conditions. They also reported sleeping better and using less prescription medications. For example, study participants reported a 42 percent reduction in the use of opiates.

Gruber said in a statement that the reduction in opiate use is a significant finding and “certainly warrants deeper and broader investigation.”

Continued Study

Researchers plan on continuing the study for two more years, further exploring the long term effects of medical marijuana on brain function.

In the statement, Gruber emphasized that there is a difference between medical and recreational marijuana, with the former sometimes (although not always) having lower levels of THC than the latter. Part of the continuing study will be investigating the various compositions of different types of medical marijuana.

Gruber said her group has only one goal in their research.

“I’m only interested in the truth,” Gruber said. “That’s what our patients and our recreational users have a right to know and a right to expect from us. People are going to use it. It’s up to us to figure out the very best and safest ways in which they can do that.”