Long-Term Pot Use May Make Word Recall Tougher
Study found marijuana linked to slight drop in ability to memorize list of 15 words
By Alan Mozes
MONDAY, Feb. 1, 2016 (HealthDay News) -- People who smoke marijuana as young adults may have a slightly harder time remembering words by the time they reach middle age, a new study suggests.
However, pot use does not appear to damage or dim other mental capacities, such as the ability to think quickly, focus or problem-solve, the study authors said.
"We were really surprised by the findings," said study author Dr. Reto Auer, an academic chief resident in the department of community medicine and ambulatory care at the University of Lausanne, in Switzerland.
Pot's impact on the ability to memorize words appeared to be incremental, meaning that "the more you smoke, the lower your verbal memory," Auer said.
Still, he stressed that the results "are only associations," and not proof of cause and effect. He also said the study only examined pot's impact on verbal memory, not overall memory, and didn't assess whether participants or their friends thought pot smoking had actually left them impaired.
Auer and his colleagues reported their findings in the Feb. 1 online edition of JAMA Internal Medicine.
To explore the potential long-term impact of marijuana use, the investigators focused on nearly 3,400 white and black men and women who were between the ages of 18 and 30 when they first enrolled in a national study in 1985 and 1986.
The participants were residents of Birmingham, Ala.; Chicago; Minneapolis; or Oakland, Calif. All were tracked for the next 25 years (up until 2011), during which time marijuana use was self-reported at seven follow-up interviews.
Almost 85 percent of the study participants said they had smoked pot at some point or another, and about 12 percent said they continued to do so in middle age.
Thinking skills were assessed at the end of the 25-year study period. The testing covered verbal memory, measured by the ability to memorize and recall a list of 15 words; visual motor speed; working memory; sustained attention skills; and the ability to problem-solve and plan.
In the end, the study authors determined that middle-aged participants who were marijuana smokers when they reached the 25-year mark fared worse in terms of verbal memory and mental-processing speed.