Chronic marijuana use 'alters brain structures and affects memory'

Marijuana use can create changes in the brain that resemble those caused by schizophrenia, according to a new study. Researchers have found that teenagers who smoked marijuana every day for around three years were affected by changes in their brain that caused reductions in memory. 

A study from Northwestern Medicine revealed that heavy marijuana usage altered structures in the teenagers' brains that resulted in them performing badly on memory tests. These abnormalities were seen when the individuals were in their early twenties, around two years after they stopped smoking the drug. This suggests that marijuana could be responsible for long-term effects following heavy use.

According to the study, the areas of the brain that are related to memory appeared to collapse inwards and to shrink. This suggests that the drug could have led to a decrease in neurons within these areas of the brain. It was also found that abnormalities in the brain that were related to the smoking of the drug, affected the performance of individual's memory and appeared similar to those found in the brain of someone with schizophrenia. These changes to brain structure could cause alterations in the way that the brain functions. 

The study is the first that looked at brain regions within the subcortical gray matter in those that have been heavy users of marijuana. It used structural MRIs to target these areas and to correlate and abnormalities in regions that could affect working memory. 

It was found that individuals had more brain abnormalities if they began using the drug at a younger age. This suggests that the affected brain regions could be more susceptible to damage if chronic use of marijuana starts earlier. 

Matthew Smith, lead study author and assistant research professor in psychiatry and behavioural sciences at Northwestern University Feinberg School of Medicine, said:  "The study links the chronic use of marijuana to these concerning brain abnormalities that appear to last for at least a few years after people stop using it. With the movement to decriminalize marijuana, we need more research to understand its effect on the brain."