Marijuana's Unknown Risk

The risks of drinking alcohol seem to be public knowledge, which can be life saving in many instances. For example, we are aware that while most people can use alcohol in moderation and be okay, while others are at risk for alcoholism.

Marijuana is similar to alcohol in that most people can use it moderately without suffering any long-term repercussions. However, what fewer people know about is the connection between marijuana use and severe mental illness (meaning that it can have psychotic symptoms), specifically schizophrenia and bipolar disorder. As with alcohol or any other substance, it’s important to understand the risks that using marijuana poses, so you can make informed choices.   

The Link Between Marijuana and Mental Illness

At time of writing, researchers do not fully understand the connection between marijuana use and mental illness. They have, though, developed several theories.

First is that individuals who are already predisposed to schizophrenia and/or bipolar disorder may be using the drug to self-medicate their symptoms. If that’s the case, by the time a diagnosis is made, it’s impossible to ascertain if the symptoms of mental illness were present before drug use began.

A second theory posits that brains predisposed to mental illness find marijuana use more pleasurable than the average brain, leading to higher rates of drug abuse among individuals with clinical diagnoses.One study found that “early use and heavy use of cannabis are more likely in individuals with a vulnerability to psychosis.”

Finally, some researchers theorize that marijuana use directly contributes to an individual actually developing mental illness.

More research is necessary in all three cases.  

What Do We Know about Marijuana and Mental Illness?

  • Research  shows that marijuana use by individuals born with two types of genes  increases the chance of developing schizophrenia.

  • Studies show that pre-illness cannabis use causes earlier onset and more severe symptoms for individuals predisposed to schizophrenia and bipolar disorder (1).

  • Marijuana use before adulthood (age 18) increases an individual’s chance of developing early-onset schizophrenia (1).

  • NPR’s article on new research showed daily use of high potent cannabis quadruples the risk of psychosis.

Marijuana Use as a Lifestyle Choice

Just like alcoholism, individuals cannot know for certain if they are predisposed to a mental illness or if cannabis use will increase the chances of developing one.  That said, there are some risk factors that you can be aware of to make better decisions about marijuana use.

Think of marijuana use like any other lifestyle choice.  If you know, for example, that you have a higher risk of getting a certain type of cancer or other disease, you can decrease that risk by making conscious choices about the foods you consume and the activities you engage in.  Doing so doesn’t automatically guarantee that you won’t get cancer, but your choices can reduce or increase your chances.

Marijuana and Higher-Risk Individuals

People who have medical histories like the following may be more at risk for developing a mental illness as the result of marijuana use.

  1. Those with mental illness in their family history, especially schizophrenia and bipolar disorder.

  2. Those who use marijuana before age 18.

  3. Those who are heavier and more frequent cannabis users than the rest of their peer group.

  4. Those who use marijuana to fight feelings of depression and anxiety when not prescribed by a doctor.

  5. Those who exhibit premorbid signs of schizophrenia, which can look like anxiety, depression, and social withdrawal.

  6. Those who exhibit any of the prodromal phase symptoms.

  7. Those who use high potent cannabis on a daily basis.

Note: Having one or more of these traits does not mean that you will eventually develop a mental illness. If you are concerned about your chances, however, it’s a good idea to see a qualified medical health practitioner, as the sooner one seeks treatment, the better the prognosis.

Note: I am not trying to debate the merits of medicinal marijuana. I am simply offering information about the potential risks of cannabis use for some individuals.

  1. Ringen, P., Nesvåg, R., Helle, S., Lagerberg, T., Lange, E., Løberg, E., . . . Melle, I. (2016). Premorbid cannabis use is associated with more symptoms and poorer functioning in schizophrenia spectrum disorder. Psychological Medicine, 46(15), 3127-3136. doi:10.1017/S0033291716001999