A recent study published in the Hippocampus journal concludes that those who used cannabis frequently in their youth have a higher chance of suffering from poor memory than non-pot smokers.

The study was conducted by researchers from the Northwestern University of Chicago and confirms a previous 2008 Australian study that linked heavy-marijuana use to development of an abnormal brain structure.

The study was done on 97 participants, both with or without mental illnesses and a heavy pot-smoking history. The marijuana users were selected on the basis of not having consumed other drugs and had used the substance daily in age periods between 16 and 20. Participants were also selected from those that had reported not using the drug in the past two years.

They were required to take a “narrative memory” test, where they were asked to recall as many details as possible from short stories they were told 20 to 30 minutes prior.

Former pot users scored on average 18% worse than their marijuana-free counterparts, with participants diagnosed with schizophrenia having scored 26% worse if they used to be heavy pot smokers. The research also confirmed past study that indicated heavy marijuana users display an abnormally structured hippocampus, a part of the brain which is very important for the ability to remember specific events. This might suggest the neuron and axons inside that part being damaged by heavy pot use.

The degrees of abnormality in hippocampus shape were higher for those who admitted to the longest term of frequent marijuana use.

However, the study is inconclusive as it stands, as while various degrees of marijuana use seem to match corresponding degrees of abnormal brain structure, the relation between the two can only be implied. A study done on a longer time period would be the only one capable of proving the link between pot smoking and poorer memory.

Marijuana use is increasing in the United States and several states have already legalized it for private use. The latest debate concerning the legalization of THC based smoking substances has the country capital’s District of Columbia stand-off with the Republican-led Congress, with an overwhelming popular support being gathered by legalize campaigns.

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