Cognitive Deficits Associated With Heavy Marijuana Use Appear To Be Reversible (Site) - Report in 2002 about a study showing that memory and learning problems caused by heavy marijuana smoking persist for at least a week after cessation of use of the drug, but they appear to resolve completely within a month. The study was supported by the National Institute on Drug Abuse.
Cognitive Deficits in Marijuana Smokers Persist After Use Stops (Site) - Report in 2003 about a study showing that cognitive impairments resulting from smoking marijuana can last up to at least 28 days after an individual last smoked the drug. The study was supported by the National Institute on Drug Abuse.