Who Uses Marijuana for Medical Purposes?

Over half of the U.S. states have approved marijuana for “medical” purposes, with three states joining the list after the November 2016 elections. Although limited evidence suggests that marijuana has analgesic effects (Clin J Pain 2013; 29:162) and could substitute for more harmful long-term prescription opioid use in individuals with chronic pain (J Pain 2016; 17:739), concerns remain that medicalization is often a gambit for legalized recreational use or that some patients use cannabis to “take the edge off” nonmedical distress. In contrast, adverse effects, especially with regular marijuana use (as is common in medical users), have been conclusively documented: harm to the adolescent brain, (J Neurosci 2014; 34:5529), reduced cortical gray matter in adults (Proc Natl Acad Sci U S A 2014; 111:16913), diminished cognitive function (Biol Psychiatry 2016; 79:557), and increased risk for psychosis (Lancet Psychiatry 2015; 2:233) and vehicular accidents (BMJ 2012; 344:e536).

A recent analysis of survey data on 96,100 adults in all 50 U.S. states further informs the debate (JAMA 2017; 317:209). Researchers compared the mental and physical health of past-year marijuana users (12.9% of participants) according to whether use was medical (0.8%), recreational (11.6%), or both (0.5%). Medical users and recreational users had similar rates of heart disease; hypertension; diabetes; asthma; hepatitis; HIV/AIDS; major depression; suicidal ideation; illicit-drug use disorders; use of tobacco, cocaine, hallucinogens, heroin, and inhalants; and nonmedical use of sedatives. However, compared with recreational users, medical-only users had higher rates of anxiety disorder, perceived poor health, and disability; reported lower use of alcohol and nonmedical use of stimulants and prescription analgesics; and were more likely to use marijuana daily. Less use of nonmedical prescription-analgesics might be consistent with use for pain. Higher anxiety rates could indicate periodic withdrawal reactions due to daily use, the development of anxiety resulting from regular use, or perhaps heightened emotional distress due to poorer health, suggesting that use may be directed at relieving distress rather than treating specific medical conditions.

These findings are consistent with those from earlier, smaller studies. One that I published last year (Am J Addict 2015; 24:599) documented poorer perceived health status, more pain, and greater physical disability in medical vs. recreational users, although the effect size was small. The only differences in medical illness were greater rates of connective tissue/skeletal disease and cancer in medical users. Similar proportions of medical and recreational users used ≥2 other illegal drugs (48% and 58%), although medical users were less likely to have severe drug problems. My conclusion from these studies: Medical and recreational users had many more similarities than differences, and the differences were small, suggesting that only a few “medical users” were likely targeting medical conditions.

One can imagine cancer sufferers using marijuana for nausea and pain, and chronic pain sufferers unable to wean themselves from prescription opioids substituting marijuana. But one can also imagine many others using marijuana as a rapidly acting, anxiolytic, and antistress medicine similar to a benzodiazepine — without randomized, controlled evidence of efficacy, knowledge of dosing strategies, or understanding of long-term adverse effects, tolerance, and withdrawal phenomena and mechanisms.

Longitudinal evidence is contradictory regarding whether marijuana use increases the risk for subsequent anxiety or mood disorders (BMC Psychiatry 2014; 14:136; JAMA Psychiatry 2016; 73:388; and Psychol Med 2014; 44:797). Still, cannabis use might adversely affect people who already have symptoms of anxiety and depression. In my practice, users already suffering from these symptoms experience further harmful effects that uniformly improve with cessation of the drug. Although animal models show that the endocannabinoid system is involved with stress and anxiety reactions, there is no human evidence that plant marijuana treats these conditions, especially as various cannabinoids can have opposing actions.

Until solid research can clearly identify whether and to what extent marijuana has medical benefits, anecdote and emotion may continue to drive the behavior of patients, doctors, and state legislatures. I strongly suggest that physicians pursue standard medical approaches before considering medical use of marijuana. In my practice as a psychiatrist, there are innumerable, evidence-based pharmacotherapies and psychotherapies for emotional distress. The rapid-acting nature of marijuana, along with its relaxing and euphoric effect, is clearly seductive for patient and doctor alike, but its long-term effects are unpredictable.