Marijuana and impaired memory
By Margaret Rogers
The medical use of marijuana to treat conditions such as pain, seizures and other ailments can have adverse 
consequences on the working memory. That is the process of being able to hold and use information for reasoning, understanding and learning.
New light is being shed on the source of this type of memory loss by researchers in Canada and France. Their study can be found in the Cell Press journal ‘Cell’.
The researchers suggest that the reason for memory lapses when using marijuana lies in the major psychoactive active ingredient known as THC. THC impairs memory quite independently from its direct effects on neurons, the study suggests. The side effects originate from quite a different source. It is the drug’s action on astroglia, which are the passive support cells that have long been thought to play a secondary role to active neurons.
Giovanni Marsicano of INSERM in France sais ‘We have found that the starting point for this phenomenon, the effects of marijuana on working memory, is the astroglial cells.’
Xia Zhang of the University of Ottawa added ‘This is the first direct evidence that astrocytes modulate working memory.’
For the past 100-150 years astroglial cells (astrocytes) have been given secondary importance by being considered as the cells that support, protect and feed neurons, explained Marsicano. Over the past ten years evidence has amassed which suggests that these cells play an important role by forging connections from neuron to neuron.
The discovery that marijuana causes memory difficulties in this way was not the intention of the study. The researchers initiated their study to see why the receptors that respond to THC and signals which are naturally produced in the brain are both found on astroglial cells.
The researchers note ‘The study shows that one of the most common effects of cannabinoid intoxication is due to activation of astroglial CB1Rs’.
