Those opposed to marijuana sometimes argue that the substance fries your brain, but new research published earlier this year in the Journal of Neuroscience found that marijuana does not kill brain cells. In fact, marijuana can actually have a positive impact on a person's mental health, as ATTN: has noted before.

The Journal of Neuroscience report is bolstered by a 2003 study conducted by the Journal of the International Neuropsychological Society, which came up with similar results regarding the effect of marijuana on the brain. Though the 2003 research found that chronic marijuana users may experience a reduction in the ability to remember and learn, other cognitive abilities were not impacted, and "from a neurocognitive standpoint, the small magnitude of these effect sizes suggests that if cannabis compounds are found to have therapeutic value, they may have an acceptable margin of safety under the more limited conditions of exposure that would likely obtain in a medical setting," the study found. 

Last year, Northwestern University published a study that found marijuana can cause brain abnormalities, but the research was swiftly questioned by UC-Berkeley professor and computational biologist Lori Pachter.

"The paper is terrible on a number of levels," Pachter told The Huffington Post of the study last year. "It reeks of dishonesty ... Maybe users have strange brains because they smoked pot. But maybe they smoke pot because they have strange brains. There is an important difference here."

Harvard researchers also found that marijuana had no long-term effect on people who stopped using the substance, although study author Harrison Pope said it's probably unwise to "try landing a 747, driving a bus or train, or taking a calculus test a week after heavy marijuana use."

The health benefits of marijuana

Dr. Sanjay Gupta, CNN Chief Medical Correspondent, wrote in 2013 that he regretted previously holding an anti-marijuana stance. After traveling around the world and meeting with farmers, experts, medicinal users, and medical leaders, Dr. Gupta's opinion on the substance shifted significantly.

"It doesn't have a high potential for abuse, and there are very legitimate medical applications," Dr. Gupta wrote. "In fact, sometimes marijuana is the only thing that works. Take the case of Charlotte Figi, who I met in Colorado. She started having seizures soon after birth. By age 3, she was having 300 a week, despite being on seven different medications. Medical marijuana has calmed her brain, limiting her seizures to 2 or 3 per month."

That said, Dr. Gupta wouldn't recommend marijuana to children or young adults as their brains are still developing. 

Earlier this year, Dr. Vivek Murthy, the U.S. Surgeon General, acknowledged the health benefits of medicinal marijuana in some situations.

"We have some preliminary data showing that, for certain medical conditions and symptoms, that marijuana can be helpful," Dr. Vivek said on CBS News. "We have to use that data to drive policy-making."

Marijuana can also be good for those suffering from mental illness. Last year, a study published in the journal Neuropsychopharmacology found that it could help treat Post-Traumatic Stress Disorder (PTSD), and a few months ago, University of Buffalo Institute on Addictions researchers found that THC, the active compound in marijuana, could reduce the effects of depression. 

“Using compounds derived from cannabis – marijuana – to restore normal endocannabinoid function could potentially help stabilize moods and ease depression,” Dr. Samir Haj-Dahmane, the study’s lead researcher, said in a press release.

Last week, Oscar-winning actor Morgan Freeman talked about his experience using marijuana to treat pain following a car accident seven years ago.

“Marijuana has many useful uses,” Freeman told The Daily Beast. “I have fibromyalgia pain in this arm, and the only thing that offers any relief is marijuana. They’re talking about kids who have grand mal seizures, and they’ve discovered that marijuana eases that down to where these children can have a life. That right there, to me, says, ‘Legalize it across the board!’ Now, the thrust is understanding that alcohol has no real medicinal use."