Marijuana is probably the most commonly used drug in America today. It is still illegal federally but as of June of this year, it is now medically legal in thirty states across the country. In nine of those states, it is legal recreationally as well. A Gallup poll done in 2017 showed that 64% of participants were in favor of cannabis legalization and in that same year legal sales reached almost $10 billion. That number constitutes a 33% increase in sales from the previous year. Marijuana use continues to rise as well.

While I was in treatment, one of the groups we had was about Cannabis Induced Psychosis (CIP). The topic was riveting to me. I was a heavy marijuana smoker for a long time. And although it was unrelated to marijuana use I have experienced a severe psychosis-like episode as a result of opiate use and sleep deprivation during which I was restrained and sedated in an ICU for three days. That experience was so intense, it has left me with vivid, indelible memories of the altered reality that I was in. Ever since then I’ve been fascinated by psychiatric conditions, especially as they relate to drug use. In doing research on the subject I came across a lot of information on CIP. The studies of the condition are fascinating but scary.

Google Dictionary defines psychosis as “a severe mental disorder in which thoughts and emotions are so impaired that contact is lost with external reality.” Psychosis is not a disease in and of itself, it’s a symptom of something larger. Common causes are schizophrenia, brain injury, bipolar disorder, and substance-induced psychotic disorders. People suffering the effects of psychosis can have visual and auditory hallucinations. Delusions make it difficult to differentiate between what is real and what is imagined. They can become paranoid and think that people are spying on them or coming to get them. They may exhibit strange behavior and speak incoherently. A common experience that I’ve heard from people who were up for days on meth was “shadow people” in the trees and on the lawn outside the house, peeking through the windows, planting bugs inside, and about to kick the door in at any moment.

While psychosis can be induced by several different drugs, marijuana is proving to be the most prevalent cause reported by doctors treating it. As the usage of cannabis has been dramatically increasing over the last several years, so have cannabis-related emergency room visits. A web search on that topic revealed all kinds of current articles that report significant increases in many states. The most current information I could find on a nationwide basis is from 2011. According to the Substance Abuse and Mental Health Services Administration (SAMHSA), of 1.25 million ER visits that year related to illegal drugs, about 36% were from marijuana. That number had increased by over 50% from 2004.

The main psychoactive ingredient in marijuana that produces the high is Tetrahydrocannabinol (THC). It’s also the chemical that causes CIP. Today, there is cannabis available that is incredibly potent, much stronger than what’s been available in the past. High Times’ Cannabis Cup of 2016 listed the strongest strain at 34% THC. There are also concentrates on the market that are up to 80% THC, probably even higher as of this writing. To give smokers the strongest high, some marijuana producers grow strains with high THC content and low cannabidiol (CBD) content. CBD is a non-psychoactive chemical that counteracts the effects of THC. Many scientists believe that the widening gap between THC and CBD in cannabis plays a big part in the increased number of CIP incidents.

CIP symptoms are similar to what can be seen in schizophrenia and other mental illnesses; confused thinking, delusions, paranoia, social phobia, and strange behavior. They can occur while the person is intoxicated or after use has stopped, usually within the next few days. CIP is temporary but effects can persist for days or weeks because of THC’s long half-life. It can take up to 30 days or longer to fully leave the body. There is a greater risk of experiencing CIP with long term use of cannabis, with larger doses, and with a higher THC content. For most people, the psychosis will completely abate with continued abstinence.

Cannabis use can cause temporary psychosis but it may also play a role in long term mental illnesses like schizophrenia and bipolar disorder. There have been several studies that, combined, followed hundreds of thousands of people over the course of decades. With the exception of one study, they all showed a correlation between schizophrenia and marijuana use. One of the most intriguing studies I found followed 6,700 people in Denmark who had been treated for drug induced psychosis and who had no prior diagnosis of a mental illness. The researchers found that, over 20 years, about 41% of the people who experienced psychotic reactions to marijuana developed schizophrenia.

There are some scientists who say that this isn’t definitive proof, that it’s correlative but not causal. It only shows that people who are developing schizophrenia are more likely to be pot smokers. They may be more likely to self-medicate with marijuana to try and feel normal. Some scientists think that people who are already genetically predisposed to schizophrenia and bipolar disorder are more likely to experience CIP. They say that marijuana can exacerbate the symptoms but that it does not cause them. However, smoking marijuana with these high-risk genes can greatly increase the probability of developing one of these permanent disorders.

A review of different studies by the National Institute of Health states that cannabis meets many but not all the requirements of causality related to schizophrenia. Because of that, from a public health standpoint, it should be given serious consideration.

What I took away from my own research into CIP and schizophrenia is that although the evidence is not concrete, most scientists conducting studies into the subject believe that CIP can be an indicator of developing a psychotic illness. Furthermore, continued use of marijuana greatly increases that chance. The amount and potency of the cannabis used is also a major factor.

It was also largely agreed upon that young people who start smoking pot in their teens are at the greatest risk. The brain is still developing up until or through a person’s 20’s and psychotic disorders typically develop in the late teenage years. Heavy cannabis use has been shown to have a negative effect on the formation of neural pathways during this time. While the vast majority of marijuana smokers never experience CIP, researchers have said that the earlier and heavier someone starts smoking, the more likely it is that they will develop a disorder at some point.