Research into the effects of cannabis on the brain is ongoing, but most experts agree that the impact of marijuana use on the fully developed adult brain is relatively insignificant. The effects of cannabis on the still developing brain of a child, however, could be more lasting and harmful.

What Does The Marijuana Research Say?

Florida Medical Marijuana Research

Among heavy and/or regular adult users — adults who smoke marijuana either once a day, several times a week or several times a month — some research studies have found that regular use of cannabis can lead to a slight diminishment in learning and memory. According to the Drug Policy Alliance, however, that impairment is only temporary, lasting while the user is intoxicated but not beyond.

Most studies have found that other aspects of brain functioning, such as reasoning skills, language skills, motor skills and reaction time seem unaffected in adults, even by heavy, long-term marijuana use. Furthermore, numerous longitudinal studies of adult habitual marijuana users have found their brains to be significantly less impaired in all areas than habitual users of alcohol or other drugs.

The story may be different, however, among youths who use marijuana. The brain develops rapidly throughout childhood and the teenage years, and is not considered fully mature until the mid-twenties. Thus, the teenage years are a critical period for brain development, with neurological pathways being created, destroyed and solidified in ways that will last for the rest of the person’s life. The teenage years are also the time when some young people begin using marijuana, with potentially life-long effects on their brains.

According to the 2012 National Survey on Drug Use and Health — the most recent survey available from the Substance Abuse and Mental Health Services Administration — marijuana use has been on the rise for the past decade among children aged 12 to 17, with an estimated 5% of children in that age range using marijuana for the first time in 2012, and 5.4 million people age 12 and older using marijuana on a daily or nearly daily basis the same year.

The National Institute on Drug Abuse reports that marijuana’s effects on learning and memory can be lasting or permanent in children who use the drug, and that heavy marijuana use in the teenage years can lead to a significant decrease in IQ scores. Furthermore, studies have found these cognitive losses to be irreversible. By contrast, people who began their marijuana use in adulthood have not been found to have significant decreases in their IQ or brain functioning.


Potential For Brain Changes

Much of the marijuana available today is stronger than it was several decades ago, containing higher levels of tetrahydrocannabinol, or THC — the psychoactive compound in cannabis that is responsible for the drug’s characteristic high. Reportedly, the higher the level of THC, the more changes there are in the user’s brain. For children and teenagers who use marijuana, this could have effects that last a lifetime.

Further research into the effects of cannabis on children’s immature brains is needed to determine the true extent of potential harm associated with marijuana use at a young age. The preponderance of evidence seems to show that marijuana does not cause brain damage in adults, whether by killing brain cells or otherwise; but in children who use marijuana, there does appear to be potential for brain changes, including harmful and permanent ones.


About the Author: Catherine Avril Morris writes on subjects ranging from astrology to parenting, grief, and romance novels. Her role in the 1993 cult classic film Dazed and Confused may have laid the foundation for her interest in current events related to the legalization of marijuana. Find her at