Marijuana, commonly referred to as weed, herb, pot grass ganja or Mary Jane is a greenish-gray mixture composed of the dried flowers of cannabis sativa plant. Often consumed through hand-rolled cigarettes called joints; pipes/water pipes known as bongs; brownies cookies candies etc; it may even be vaped using devices called vape pens. Cannabis has long been used both medicinally and recreationally throughout its long history.
People who use marijuana regularly and for extended periods may experience changes to brain function, including problems with learning and memory as well as decreased IQ. Studies indicate these effects can last 24 hours after marijuana use has stopped; however, other research shows long-term marijuana use, particularly among adolescents, may cause irreparable brain damage.
Researchers conducted in 2007 discovered that marijuana users performed worse on tests of attention, memory and executive functioning than nonusers. It is thought this is because THC binds with CB1 receptors located in regions important for memory storage such as the hippocampus and cerebellum and blocks their ability to store new information.
Studies have demonstrated that teenage marijuana users have smaller hippocampal volumes and reduced cortical thickness compared to nonusers, as well as reduced connections between areas in their brain that control emotion and behavior, such as the prefrontal cortex, which have fewer connections – all indicators of poorer performance at school and work. Researchers also discovered evidence of changes to white matter (nerve fibers that allow efficient communication among brain regions), likely caused by marijuana’s effects such as premature tissue development or changes to mechanics underlying structural changes.
Recent twin studies reported that those who used marijuana during adolescence experienced a significant drop in neuropsychological function as early adults, equal to roughly six IQ points lost. It’s thought that frontal cortex development is one of the last areas to take hold, making it particularly susceptible to substance usage during this crucial stage.
The Adolescent Brain Cognitive Development study, funded by the National Institutes of Health, will follow a sample of young Americans from late childhood through early adulthood to assess how marijuana and other substances impact adolescent brain function. Utilizing advanced imaging and other tools, researchers will examine whether marijuana affects specific areas of the brain associated with learning and memory and whether changes persist over time. If its results are confirmed, this research could inform decisions about when and how adolescents begin using marijuana, providing valuable insight into its impact on developing brains before making these important decisions.