Anyone who’s spent a long weekend hitting the bong knows marijuana can do strange things to short-term memory and attention span. Halfway through a sentence, a memory, a word, a closing thought will disappear, leaving listeners to wonder what you’ve been smoking.

For stoners, that’s just part of the fun. But for patients who rely on medical marijuana as part of daily life, it can be a serious problem.

The authors of a new study on mice say they’ve discovered the neural pathways responsible for these difficulties. And they believe something as simple as over-the-counter pain pills could help.

Ibuprofen“Our studies have solved the longtime mystery of how marijuana causes neuronal and memory impairments,” said study author Chu Chen of Louisiana State University’s Health Sciences Center. “The results suggest that the use of medical marijuana could be broadened if patients concurrently take a nonsteroidal anti-inflammatory drug such as ibuprofen.”

That’s because many patients who could benefit from medical marijuana can’t tolerate the side effects, said Giovanni Marsicano, a neuroscientist at the University of Bordeaux in France. Marsicano, who was not involved in the study, told Science magazine the findings could lead to significant improvements for patients and drug-trial participants.

“This is what we call a seminal paper,” Marsicano said. “Many people in clinical trials are dropping out from treatment because they say, ‘I cannot work anymore. I am stoned all the time.’”

Medical marijuana is allowed in 20 states and several countries. Pot is legal and regulated for recreational purposes in only two places: Colorado and Washington State. It will soon be legal in Uruguay. Other states and nations are likely to follow. And many patients use in states where weed is illegal.

The potential reach of this discovery, in other words, is large.

Medical marijuana is used to treat a wide range of conditions, from multiple sclerosis to the nausea that results from cancer therapies. It treats seizure disorders, chronic pain, glaucoma and HIV/AIDS. It’s been used as a medicine for at least 4,000 years.

The side effects can be troubling for some patients, though, especially those who wouldn’t otherwise use marijuana. Work, relationships, parenting and social life can all suffer.

Researchers know how cannabis works on the brain, but they don’t know exactly what causes these side effects.

Both marijuana and the human body provide the brain with chemicals known as cannabinoids. Marijuana provides THC, the chemical that makes users high, while the body produces endocannabinoids, which help regulate mood and energy, among other functions.

Both these chemicals bind to the same two receptors in the brain, CB1 and CB2. When a cannabinoid binds to CB1, researchers believed, it suppresses an enzyme known as COX-2. Ibuprofen does essentially the same thing.

Scientists had hypothesized it was this blocking effect that produced the THC side effects. In fact, the opposite turned out to be true: THC boosted COX-2 levels. Chen and his team also discovered that once the stoned mice were given ibuprofen to block the COX-2, memory and attention span increased.

As usual, experts say more research is needed. For one thing, a painkiller that inhibits COX-2 activity might also make THC less effective as a treatment for some disorders, said Raul Gonzalez, a psychologist at Florida International University. Chen’s team showed that mice modeled after Alzheimer’s patients still receive some benefits of THC even after being given a COX-2 inhibitor, but Gonzales said that doesn’t address other conditions, such as HIV/AIDS.

“It is much too early to tell, but the current study will undoubtedly spur some exciting new research,” he said in an email to Science, calling it an “elegant set of experiments.”


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