Marijuana and the Psychiatric Patient

Burns Woodward, MD;

In a widely cited 2014 article, Nora Volkow and her colleagues at the National Institute on Drug Abuse highlighted the evidence that connects marijuana use with psychosis, anxiety, depression, and addiction.¹ A second article examined its harmful effects on cognition, psychosis, and motivation.² The American Psychiatric Association’s position statement begins, “There is no current scientific evidence that marijuana is in any way beneficial for the treatment of any psychiatric disorder.”^3[PDF]

Despite near-unanimous medical warnings, marijuana use is widespread among psychiatric patients,⁴ including those with psychotic disorders.⁵ Advocates tout its benefits for anxiety, depression, and bipolar disorder⁶; and medical marijuana regulations in 9 states include PTSD as a qualifying condition. Psychiatry’s apprehension plainly disagrees with more favorable attitudes in patients and the public. How can psychiatrists best address their patients’ marijuana use in this contentious environment?

AUTHOR BIO

Dr. Woodward

is Assistant Clinical Professor of Psychiatry at Boston University School of Medicine. He is in private practice in Newton, MA.

What follows is a critical summary of the evidence now available that connects marijuana with cognitive problems, psychosis, anxiety, PTSD, depression, and addiction. I have relied on published reviews, supplemented by PubMed searches for more recent data. Be forewarned-this is an evolving picture, since credible research about the psychiatric effects of cannabis is only now emerging after decades of legal constraint. I argue that patients benefit when psychiatrists attend to their marijuana use-a hands-off approach is likely to miss an important influence on their symptoms-and that a collaborative approach can steer between the Scylla of harsh admonition and the Charybdis of naive acceptance.

The psychopharmacology of marijuana is complex. Delta-9 tetrahydrocannabinol (THC), the most psychoactive of its many cannabinoid constituents, acts on endogenous cannabinoid receptors, which, like those for monoamines and endogenous opioids, are found in brain areas subserving memory, cognition, emotions, and motivation. Cannabidiol (CBD), another cannabinoid found in marijuana, appears to counteract the psychedelic effects of THC; it is being investigated as a treatment for a number of medical and psychiatric conditions.⁷ Samples of illegal marijuana these days have very low CBD:THC ratios, which maximizes psychedelic effects, while medical marijuana is advertised with CBD:THC ratios as high as 20:1.⁸ Thus, it may be important to understand the source and purported characteristics of the marijuana a patient is using.

Extensive laboratory, clinical, and epidemiological evidence connects marijuana use to cognitive impairment, and both clinical and epidemiological data link it to psychosis. The correlations with addiction, anxiety, and depression, however, are based mainly on interviews of national population samples, which are likely to differ from patients who present for treatment. The evidence that marijuana benefits PTSD comes mostly from animal data. Table 1 summarizes this evidence, along with treatment recommendations.

Non-intoxicated regular cannabis users perform worse on global neuropsychological tests by a third of a standard deviation or less. Some evidence suggests this cognitive impairment may be short-term, with recovery occurring over days to months after cessation of use. Its extent and persistence are worse with early age of onset, high frequency, and long duration of use.² Marijuana-induced cognitive dysfunction may account for its association with motor vehicle accidents at a level approaching that of alcohol, as well as with reduced life achievement.1 Discussing patients’ marijuana use in high-risk situations, including driving and sexual activity, may be lifesaving, and exploring its effects on academic and work performance may improve outcomes.

Marijuana-related problems fall well within the scope of psychiatric practice: many patients use marijuana, which is likely to affect their psychiatric symptoms and response to treatment.

For decades, marijuana has been associated with the emergence of schizophrenia and other psychotic disorders. Recent data show that in genetically vulnerable individuals, psychotic disorders are more likely to emerge and to emerge earlier if marijuana is used.² Ongoing marijuana use by patients with schizophrenia is associated with worse outcomes.⁵ Thus, patients with individual or family histories of psychosis can be counseled that marijuana use puts them at greater risk for the development or exacerbation of a psychotic illness.

The widely quoted statistic about marijuana’s addictive propensity-that a cannabis use disorder will develop in 9% of people who try marijuana-comes from a national epidemiological sample of 34,653 individuals interviewed in 2001 to 2002 and again in 2004 to 2005. The researchers found marijuana less addictive than nicotine (the corresponding figure is 68%), alcohol (23%), and cocaine (21%). For psychiatric patients, however, the picture is far bleaker. In the study, individuals with psychotic or conduct disorders who used marijuana had double the risk of addiction; triple the risk of mood, anxiety, and attention deficit disorders; quadruple the risk of personality disorders and alcohol dependence; and cocaine dependence increased the risk by a factor of 6.⁴ In clinical practice, patients with cannabis use disorder may have great difficulty limiting or abstaining from marijuana use, which exacerbates psychiatric problems, and treatment may need to target marijuana use as well as other issues.

Earlier data associated marijuana with anxiety disorders, and it is clear that marijuana intoxication elicits panic-like symptoms and even paranoid thinking in some individuals. Recent analyses of population-based data have disagreed about how much excess risk for anxiety disorders can be attributed to marijuana use and how the risk varies among subgroups.⁹

Marijuana use is common among patients with PTSD. Animal studies have found that cannabinoids can prevent stress-induced emotional and memory effects, and preliminary studies have found reduction in some PTSD symptoms in humans. There have, however, been no large-scale, controlled studies.¹⁰ Clinicians who treat marijuana-using patients with anxiety or trauma-related disorders will need to explore the relationship of their symptoms to marijuana use on a case-by-case basis.

Although a 2003 review found elevated rates of depression in marijuana users as well as evidence of depression increasing with ongoing use,¹¹ in more recent analyses the correlation has dropped out when potential confounding factors are controlled.¹²Another review found antidepressant medication ineffective in depressed patients with cannabis use disorder, but the trials cited had very high placebo response rates, probably because of the intensive psychosocial treatments they also provided.¹³ As with anxiety disorders, it is important to explore with patients the relationship between their marijuana use and depression. Severely depressed patients may have difficulty participating in such explorations, and a trial of abstinence may be the best strategy, which may require psychotherapy or family intervention to implement.

Evidence-based treatments for cannabis use disorder include motivational enhancement therapy, cognitive-behavioral therapy for addiction, and contingency management, which are modestly effective.¹⁴ Pharmacological options are quite limited: dronabinol (THC) is effective for cannabis withdrawal, but using it for that purpose would require a legal waiver. There is limited evidence that gabapentin may relieve cannabis withdrawal symptoms, and that gabapentin and N-acetyl cysteine may be useful for cannabis use disorder.¹³

Marijuana-related problems fall well within the scope of psychiatric practice: many patients use marijuana, which is likely to affect their psychiatric symptoms and response to treatment. Table 2 lists some general principles for working with such patients. Addressing marijuana use is often an ongoing process, and it is helpful to inquire about the patient’s experience and readiness to change during each interview. The disease model of addiction can help clinicians avoid moral criticism and shaming, which tend to elicit defensiveness. Patients sometimes need education about the adverse consequences of marijuana use, but many know about the risks, and the clinical task is to help them use what they already know. Family members can provide important information for evaluation and monitoring.

While the evidence-based treatments-motivational enhancement, cognitive-behavioral therapy for addiction, and contingency management-are not part of every psychiatrist’s repertoire, basic skills in these areas are easy to learn and can be incorporated into both medically oriented and psychotherapeutic treatment. Psychiatrists who are not comfortable working in these areas can refer patients to addiction specialists, but referral is often facilitated by a motivational approach.

Our growing knowledge of the psychiatric effects of marijuana is being rapidly outstripped by increased public acceptance and legal availability. For now, psychiatrists will find it most rewarding to approach their patient’s marijuana use in a spirit of inquiry and collaboration to guide them toward effective self-care in this important area of their mental health.

Disclosures:

Dr. Woodward is Assistant Clinical Professor of Psychiatry at Boston University School of Medicine. He is in private practice in Newton, MA.

Dr. Woodward reports no conflicts of interest concerning the subject matter of this article.

References:

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