Marijuana and the Adolescent Brain

Marijuana is arguably one of the least harmful mind-altering substances. The debate over the severity of harmfulness is controversial. Many would argue that marijuana is less harmful than alcohol, which has been a socially acceptable substance throughout most of American history, except for the period of prohibition.

However, marijuana is not harmless, especially regarding the developing brain. During childhood, the brain is larger. It prunes itself back during adolescence to streamline the thinking process. The teenage years are our last golden opportunity to make the brain as healthy as a smart as possible. Clouding the mind with marijuana during this time can lead to cognitive decline. Studies have shown an 8-point decline in IQ for adults who used marijuana regularly as teenagers. This cognitive decline does not appear to be present in individuals who begin using marijuana later in adulthood.

It is believed that this has to do with the prefrontal cortex not being full developed until the age of 25. Thus, the earlier the age of onset of marijuana use and the increased frequency and amount of the use leads impacts the severity of cognitive decline in processes performed by the pre-frontal cortex, such as executive functions, attention, and memory. Examples of executive functions are organizing, prioritizing, regulating alertness, adjusting processing speed, modulating emotions, managing frustration, holding on and working with information, retrieving memories, and monitoring and regulating one’s actions.

Marijuana does not appear to have catastrophic consequences on these processes for an adult, once the pre-frontal cortex has had time to fully develop. Thus, marijuana should not be demonized as a horrible substance or portrayed as “the devil’s lettuce.” It does not make people go mad, as depicted in the 1939 propaganda film “Reefer Madness.” The harmful consequences are much subtler and covert, which is why 60% of teenagers believe it to be safe.

Many adolescents and adults choose to use marijuana because it cultivates divergent thinking (free-flowing, spontaneous, and creative thought). It appears to induce a state of hyper-priming, which extends outwards to distantly related concepts. For example, someone hears “dog” and thinks of nouns that, in a more sober circumstance, would seem to have nothing in common with a dog. This can be very helpful for creative tasks. However, obviously, you don’t want too much hyper-priming, or else everything seems connected and the web of associations becomes a source of delusions.

With marijuana laws becoming more and more laxed across the United States, it is important that teenagers understand the possible consequences of using marijuana during their adolescent years, especially if they are using it regularly. Marijuana is not a horrible drug, but it is also not harmless and teens should be mindful the impact it has on their adolescent brain development.