Regular use of cannabis can lead to impairments of real world memory, according to a study published in the Journal of Psychopharmacology in 2008.
The study was conducted by Dr. John E. Fisk and Dr. Cathy Montgomery.
For their study, Fisk and Montgomery recruited users of cannabis and those that had never used any illicit substance. Those who used illicit drugs in addition to cannabis were excluded from the study.
Fisk and Montgomery also took the use of alcohol and tobacco into consideration.
The users and non-users then received a number of tests designed to measure executive component processes, associative learning, everyday memory, prospective memory, and cognitive failures. The last three of these measures, everyday memory, prospective memory, and cognitive failures, were in the form of self-reported questionnaires.
“The results obtained failed to reveal cannabis-related deficits in executive component processes and associative learning. However, cannabis use did appear to adversely affect real-world memory functioning. Cannabis users were impaired on all three measures, everyday memory, cognitive failures and prospective memory.”
The three measures of real-world memory – everyday memory, cognitive failures, and prospective memory – assessed lapses of memory in everyday activities, such as while watching television; general cognitive problems, such as failing to notice a stop sign or bumping into others; and remembering to perform an intended action, such as forgetting to turn off your alarm clock in the morning.
As noted by Fisk and Montgomery above, no deficits in executive processes or associative learning were discovered compared to those that did not use cannabis.
JE Fisk & C Montgomery. (2008). Real-world memory and executive processes in cannabis users and non-users. Journal of Psychopharmacology, Vol 22, No 7: 727–736.