In the study, 97 participants with some having a history of smoking marijuana as teenagers and others who didn’t were followed to track their evolution. The study found that after giving up the habit those who abused the substance had the worst scores on assessing their long-term memory. More than 80 percent of those who smoked reported using the marijuana every day, said lead study author Matthew J. Smith, assistant professor of psychiatry and behavioral science at Northwestern University Feinberg School of Medicine.
“[The] hippocampus itself serves as a major player of the formation of our new memory or long-term memory and spatial navigation, abilities that we need in everyday life,” senior study author Lei Wang, assistant professor of psychiatry and behavioral sciences at Northwestern University.
In another research, authors noted that the schizophrenia patients who reported using marijuana scored the worst on memory tests, which involved a standardized method of hearing a story and being asked to recall certain details 20 to 30 minutes later. Schizophrenia patients who reported smoking marijuana daily scored 26 percent worse on the long-term memory tests compared to the schizophrenia patients who didn’t smoke weed.
Among the psychologically healthy patients, those who smoked marijuana scored 18 percent worse on the memory tests than those who didn’t smoke.
“We’re in the Prohibition-era of marijuana, and I say this as an analogy because during Prohibition there was no alcohol available in restaurants or that could be sold, and people were brewing it at home and because they were brewing it at home, they didn’t know what the alcohol content was,” Smith said. “And we do know more potent THC is linked to poorer memory and a higher risk of psychotic-like experiences.”
The findings were published in the journal Hippocampus.