Teen cannabis users have bad long-term memory in adulthood

Teens who were serious marijuana users – smoking it regularly for about 3 years – had an abnormally shaped hippocampus and worked badly on long-term memory jobs, report a new Northwestern Medicine study.

The hippocampus is vital to long-term memory (also called as episodic memory), which is the capability to remember life events or autobiographical.

The memory problems and brain abnormalities were observed during the individuals early twenties, 2 years after they prevented smoking marijuana.

Young adults who badly treated cannabis as teens performed about 18% bad on long-term memory tests than young adults who never badly treated cannabis.

“The memory works that appear to be affected by cannabis are ones that we use daily to solve general problems and to sustain our relationships with family and friends,” Dr. Jon Csernansky (senior author), the Lizzie Gilman professor behavioral sciences and chair of psychiatry at Northwestern Memorial Hospital and Northwestern Feinberg School of Medicine.

The study will be released 12 March in the Hippocampus Journal.

The study is among the initial to say the hippocampus is shaped differently in big marijuana smokers and the different looking shape is openly related to bad long-term memory performance.  Previous studies of cannabis users have presented either the strange shaped hippocampus or bad long-term memory but none have attached them.

Previous research by the same Northwestern team presented bad short-term working memory performance and bad shapes of brain structures in the sub-cortex including thalamus, striatum, and globus pallidus.

“Both our new studies link the chronic use of marijuana during adolescence to these differences in the design of brain regions that are important to memory and that appear to last for at least a few years after people prevent using it,” said Matthew Smith (lead study author), assistant professor of behavior sciences and psychiatry at the Feinberg School of Medicine.

The extensive the individuals were chronically using marijuana, the more bad the shape of their hippocampus, the study reports. The finding advice that these regions related to memory may be more liable to the effects of the drug the longer the abuse occurs.

The bad shape likely reflects problems to the hippocampus and could include the structure axons, neurons or their supportive environments.

“Advanced brain mapping instruments permitted us to examine detailed and sometimes subtle changes in little brain structures, including the hippocampus,” Lei Wang said, also a head study author and an assistant professor of behavioral sciences and psychiatry at Feinberg. The experts sued computerized programs they developed with collaborators that performed perfect mapping between structural MRIs of different individual brains.