In the November 2018 edition of Psychiatric Services Mary Brunette, MD, et. al., published a brief update on this timely question above. In the following blog post the reader should assume the material is taken directly from that review. Secondary references are contained within the article and the interested reader is referred to that article for further attribution and more in depth inquiry.
Thirty-three states and the District of Columbia have substantially reduced barriers for the sale and use of marijuana either through the legalization of medical and/or recreational marijuana or the decriminalization of the possession and use of marijuana. In Washington state 20,000 pounds of marijuana are produced each month. In addition, the marijuana industry has developed an array of products and delivery methods such as smoking, edibles, and concentrates. In addition, the industry profiles customers and heavily advertises to consumers. This all raises the question inferred in the title of this blog.
To borrow a phrase from an old Buick commercial, "this ain't your daddy's marijuana". When I was in college the THC content (the component in marijuana that gives you a high, the other component of marijuana CBD does not have euphoric/sensation altering properties) was anywhere from virtually non-existent to about 4%. Today the average street marijuana has a THC content of about 12% while the CBD component has decreased leading to a more rapid and potent high. Through genetic manipulation that would be the envy of Gregor Mendel and post harvest manipulation, we now have various products that vary the THC and CBD to produce custom products that allegedly have varying psychological effects. A sample of the offerings in Washington State include, Gorilla Glue Ethanol Shatter, with 75.8% THC potency; Billy Club Sativa, with 19.04% THC and <.05% CBD potencies; and Shark Shock Flower, with 9.21% THC and 11.8% CBD potencies. Marijuana is no longer, and perhaps never was, one entity but a variety of products with varying potencies, THC:CBD ratios, and CNS and peripheral nervous system effects.
What does this mean for the person with a serious mental illness such as schizophrenia or bipolar disorder? Psychiatrists have known for several decades that potent THC can cause psychotic symptoms in psychotic and non-psychotic individuals. When used heavily in adolescence THC increases the risk of developing schizophrenia. In patients that already have schizophrenia, THC worsens the symptoms and course of the illness. Heavy THC usage is associated with an increased risk of developing mania and depression, and in patients with a pre-existing mood disorder is associated with exacerbations of depression and mania. There is a common folk knowledge that marijuana is helpful in the treatment of PTSD but there is not a single controlled prospective published study of marijuana for this condition and retrospective, uncontrolled studies have been mixed.
Whether CBD is helpful for people with certain mental illnesses is unknown. (Part of the reason for the unknowing is that marijuana is illegal at the federal level. The DEA classifies marijuana as a schedule I drug. Researchers find grant money non-existent and all the marijuana that is used must be obtained from the farm at Ole Miss which is a strain from the 1960's). There was a study published in 2018 using a preparation of CBD without THC that reduced psychotic symptoms among people with schizophrenia. Beyond that, we do not have much evidence on which to hang our clinical hat.
In conclusion, outside of schizophrenia, bipolar disorder and use in adolescence, the evidence for benefit or harm from marijuana is anecdotal and conflicted owing to a lack of quality, prospective, controlled studies. Our current understanding is that marijuana is not universally good nor universally bad. However, it is not inconsequential. For patients in my clinic, I address marijuana use as another clinical factor that should be addressed with the patient. We do know the physiological effects of THC and CBD. We also know the the physiologic effects of the FDA approved medication we use every day in the clinic. In devising with the patient a treatment plan we must take all of this into consideration.