To say that recreational use of marijuana is an anathema to memory is to highly overstate the claim. Not all memory is created equal, nor does the smoking of marijuana affect adolescents the same as adults, or males the same as females.

While there are some irrefutable instances of cause and effect between smoking weed and forgetting any number of important notions (that may keep you out of trouble), there are numerous factors to take into account.

Memory Loss in Adolescents

There can be no doubt that the heavy and chronic use of cannabis by adolescents causes memory problems. Excepting for cases where it is used for medicinal uses, marijuana use by teens should clearly not be encouraged.

This is not to say that an occasional joint is going to do any long-term harm, but given that the adolescent brain is much more vulnerable to the potentially negative effects of cannabis, it should be avoided.

What’s more, a UK study revealed that adolescents experience less of a satiety effect after smoking marijuana than adults, so they are inclined to consume greater quantities of cannabis than adults.

Adolescence is the period in human development when the processes that refine and strengthen neural networks occur, and they continue on until a person reaches their mid-20s.

Brain matter and integrity of that matter increase during this period of life. Heavy usage of marijuana during this time affects the “wiring” of the brain and as such can inhibit myriad memory functions.

Numerous studies on the matter have shown that the regular adolescent users of marijuana consistently perform poorer in cognitive functions than their non-using peers.

Most types of memory are negatively impacted by adolescent abuse of marijuana. Executive memory, which is the type of memory used to assist in planning, reasoning, and problem solving, is particularly affected, as is the processing speed of the information.

Frequent adolescent marijuana smokers also show a higher rate of impaired verbal memory and story memory than non-using peers. Interestingly, other types of memory such as associative and visuospatial memory do not seem to be impacted.

It also seems that memory loss in adolescents does discriminate; female, heavy users of marijuana show poorer episodic memory than their male, heavy-using peers.

All is not lot lost though for younger cannabis connoisseurs, however. As more studies are performed, the less evidence there is for any correlation between lower IQs and recreational marijuana usage.

Even better is that after a three-month hiatus of using marijuana, most cognitive functions return to normal peer levels. One study has even shown that among college students (technically young adults, not adolescents), recreational marijuana usage results in higher, mental processing speeds as compared to their non-smoking peers. Don’t take that one to the bank just yet, as the results of that one study could just be an anomaly.

The most recent data suggests that marijuana usage among adolescents is at an all-time low since the 1970 declaration of marijuana as a Schedule 1 substance, but is trending upwards again.

Six per cent of American high school seniors admit to smoking marijuana on a daily basis and 21 per cent admit to being regular smokers of cannabis. For comparison, less than 10 per cent of the overall United States population (22.2 million) report marijuana use in the past month.

Memory Loss in Adults

There is no shortage of hard evidence linking the chronic and heavy use of marijuana to cognitive deficiencies in adult users. Large-scale studies, such as a Swedish study of more than 50,000 individuals and a New Zealand study that followed a cohort of over 1,000 individuals for 20 years, prove that numerous types of memory are poorer by any measure for the marijuana users in comparison to peers who do not use marijuana.

Specifically, learning, working memory, and attention are affected. The silver lining (or is it Silver Haze?) is that upon abstinence of marijuana use, many (if not most) cognitive functions return to normal levels, so this can be reversible.

Of course, not all researchers agree. Some findings suggest that if the hippocampus is damaged due to heavy cannabis usage, memory loss may not be reversible upon abstinence.

Read More: Cannabis Use and Seniors

Worst-case Scenario

What would an article about the effects of using marijuana and its impact on memory loss be if it didn’t end with a nightmare-like scenario? Chronic cannabis use has been attributed in rare cases to inducing the mother of all memory loss episodes: the fugue-like state.

When someone falls into this amnesia-like state, there is no memory of one’s self; not a name, history or any idea how, when, or why they exist.

The resulting confusion usually makes the individual unstable and dangerous to him or herself and those around them.

Fortunately, relatively few persons ever experience this, and it is difficult to deduce for how many it would have occurred without the use of cannabis, since it is a psychotic state that can be triggered by numerous stimuli, including cocaine use, physical trauma, and misuse of other medications.

Read More: Cannabis Use and Mental Health: Things to Keep in Mind