Marijuana's Effect on Memory and the Brain

Though some believe marijuana is a relatively "safe" drug, studies show it impairs brain function and memory. The active chemical in marijuana, THC, alters the way information is processed by the hippocampus, which damages short-term memory capacity.

In one study, lab rats treated with THC performed poorly on tasks requiring short-term memory, similar to rats whose nerve cells in their hippocampus were destroyed. Also, rates under the influence of THC struggled most trying to perform tasks when the drug was impairing the normal function of cells in the hippocampus.

With age, the brain loses neurons in the hippocampus, which makes it difficult to remember experiences from the past. Prolonged exposure to THC may speed up this aging process in the hippocampus. For example, one study showed that rats exposed to THC every day for eight months (approximately 30 percent of their lifespan), when examined at 11 to 12 months of age, experienced nerve cell loss equivalent to that of unexposed rats twice their age.

 

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