4 Conditions That Absolutely Do Not Mix With Marijuana

Marijuana may be very much in the news, especially following legalization of recreational use in a handful of states, but that doesn’t mean the drug is completely safe universally — or at all, for that matter. Much more research will need to be done before the full extent of the risks and dangers of marijuana use — casual or medicinal— is known. But there are four conditions that absolutely do not mix with marijuana that you should know about.

Bipolar Disorder

A U.K. study from the Spectrum Centre for Mental Health Research at Lancaster University and the University of Manchester published in 2015 in PLOS ONE showed that marijuana use in the daily life of those with bipolar disorder is linked to increases in both manic and depressive symptoms. Lead study researcher Dr. Elizabeth Tyler of Lancaster said that one theory to explain high levels of marijuana use is that people use cannabis as a means of self-medicating bipolar disorder symptoms. The study looked at people who had not used marijuana in the six days prior to the start of the study. Findings suggest that cannabis isn’t being used to self-medicate small changes on a daily basis. But the use of cannabis may be associated with both positive and negative emotional states. Comments from study participants included statements that they sometimes used marijuana to lift their mood, but others reported they didn’t use cannabis to manage depression because it made it worse, and another said that excessive smoking resulted in feeling depressed for days afterward. The bottom line is that more research needs to be done to determine if these relationships play out long-term, as they could have an effect on the individual’s course of bipolar disorder. For now, however, the implication is that marijuana shouldn’t be a go-to option for easing bipolar disorder symptoms.


For those with any family history of schizophrenia, there’s an increased risk of developing schizophrenia if they abuse marijuana. This is the finding of a study conducted in 2013 by researchers at Northwestern University Feinberg School of Medicine in Chicago, Illinois. The study, published in Schizophrenia Bulletin, looked at teens who used marijuana daily for three years and performed poorly on tests of working memory and showed abnormal brain structure changes (revealed through MRIs), similar to patients with schizophrenia. Researchers said long-term marijuana use is linked with concerning brain abnormalities that appear to continue at least a few years after use stops. These changes correlated with poorer working memory and age of onset in younger patients in both healthy study participants and schizophrenic marijuana users. Study authors stated that their data is cross-sectional and therefore cannot indicate causality. Clearly, more statistical testing needs to be done with schizophrenia patients to determine whether cannabis use has more of an impact on schizophrenia patients than healthy controls.


With psychosis, the link to excessive marijuana use isn’t with individuals who already have a psychosis but those who are more at risk of developing a serious psychosis as a result of heavy marijuana use, especially from high-potency cannabis. That’s the conclusion of scientists at King’s College London who conducted the study, published in Lancet in 2015. Researchers said that young people need to be advised of the risks. The study referred to the potency of so-called “skunk strains” vs. that of ordinary “hash,” saying that those using weaker forms of cannabis didn’t seem to have the same increase in risks. Skunk is so powerful, said researchers, that users are three times more likely to suffer a psychotic episode than those who have never used the super-potent pot. In addition, researchers said that skunk use by itself was responsible for 24% of the adults presenting for first-episode psychosis to South London psychiatric services. For heavy users, daily or weekly, risks jump to an increase ranging from 50% to 200%.


Research on marijuana’s effects on pregnancy show a concerning and, in some cases, troubling amount of evidence that marijuana can cause serious long-term effects on the child. These range from difficulties with birth, premature birth, abnormalities in the child’s brain structure that can cause later difficulties with executive and cognitive functioning, development of attention-deficit disorder and anxiety or depression, among other negative consequences. A study by the Karolinska Institutet in Sweden and the Medical University of Vienna in Australia, published in EMBO Journal January 2014, found that THC, the active ingredient in marijuana, interferes with connections being formed between nerve cells in the cerebral cortex, the part of the brain involved in memory formation and higher thinking skills. Researchers recommended that pregnant mothers avoid marijuana use altogether, including medical marijuana, as the effects of such exposure could last into the child’s adulthood. 

Surprisingly, No Link Found to Depression Later in Life

Although it had long been thought that marijuana use by teenage boys was linked with an increased risk for developing depression later in life, recent research appears to challenge that association. The American Psychological Association (APA) said in an August 2015 news release that its study of teen boys who used marijuana showed no link between marijuana use and the development of cancer, hallucinations, delusions or other psychotic symptoms later in life. It also found no association between teen marijuana use and later depression, anxiety, allergies, high blood pressure or headaches. The APA said that because the study included only teen boys, it could not draw any conclusions about females and marijuana use. Sources: Cannabis-Related Working Memory Deficits and Associated Subcortical Morphological Differences in Healthy Individuals and Schizophrenia Subjects, Schizophrenia Bulletin, Dec. 15, 2013; EMBO Journal, Jan. 27, 2014; Lancet, February 2015; The Relationship Between Bipolar Disorder and Cannabis Use in Daily Life: An Experience Sampling Study, PLOS ONE, March 5, 2015; Psychology of Addictive Behaviors, Aug. 4, 2015

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