Medical professionals have always warned people about the negative effects of marijuana on memory but haven't been able to explain why until now. An international team of scientists believe they are closer to finding out why taking cannabis impairs short-term memory.

Xia Zhang of the University of Ottawa Institute of Mental Health Research and Giovanni Marsicano of the University of Bordeaux, France came up with an explanation for the role marijuana plays in short-term memory loss by focusing on a particular type of brain cell called an astrocyte.

"Our study provides compelling evidence that astrocytes control neurons and memory," Zhang told the journal Nature. "The supporting actor has become the leading actor."

Cannabis affects the brain with a host of chemicals that leads to a change in memory and mood. The researchers have discovered that THC, the best known chemical or cannabinoid, is not acting on the brain's neurons but on the neuron support system called the astrocytes. These cells have been relegated as less important neurons but now scientists are discovering how important they really are in the brain.

The researchers studied how mice would react to marijuana's active component and several synthetic materials. They then genetically engineered mice whose astrocytes could not be affected by THC and after comparing the effects of THC on the engineered mice and normal mice they discovere that the mice without the astrocyte CB1R receptor wasn't impaired with marijuana.

The discovery could pave the way for researchers to create medical marijuana that doesn't affect the patient's working memory. Scientists have been trying to use cannabinoids to treat such medical conditions like multiple sclerosis and chronic pain. The study could also shed light on how the brain's chemical pathways work. This could lead to ways to make it work better and even find a solution to other memory problems like Alzheimers.