Cannabis and PTSD
Evidence that cannabis or cannabinoids are effective for improving symptoms of PTSD is considered limited by the National Academy report, but clinical reports and case series excluded under its research quality criteria are more positive for the benefits of cannabis for PTSD symptoms. A growing number of states have included PTSD as one of the acceptable indications for recommending or approving medicinal use of cannabis. Clinicians who have written large numbers of medical cannabis recommendations have documented that a sizeable minority have been for psychiatric indications, with PTSD being perhaps the most common.10
Greer and colleagues11 reported on 80 patients with PTSD who were approved for medicinal use of cannabis through the New Mexico Medical Cannabis program. As a retrospective assessment, the study’s methodology limits the scientific conclusions that can be drawn. However, the authors reported decreases of 75% overall and separately in each of the 3 respective (DSM-IV) symptom clusters: re-experiencing, hyperarousal, and avoidance, as measured by current versus retrospective baseline Clinician Administered PTSD Scale (CAPS) scores, with and without cannabis use, respectively. The study was not included in the National Academy report, but it was reviewed by Walsh and colleagues,1 who noted that most studies on the therapeutic use of cannabis by persons with mental health conditions are not of methodologically high quality.
The beneficial effects of cannabinoid medicines for PTSD are consistent with what is known about the psychobiology of PTSD and the emerging research on the endocannabinoid system.12 Components of the endocannabinoid system include cannabinoid (CB1 and CB2) receptors; endogenous ligands anandamide, 2-arachidonoylglycerol (2-AG), and others; and enzymes that regulate endocannabinoid ligand production. Endocannabinoid signaling occurs in retrograde fashion, with postsynaptic release of ligands that bind to presynaptic cannabinoid receptors and inhibit presynaptic neurotransmitter release. This contrasts with the classic monoaminergic neurotransmitter systems that have shaped much of our thinking in psychopharmacology, and represents a potential alternative strategy for psychopharmacologic intervention (Figure).
CB1 receptors are widespread throughout the brain. Based on animal and human studies, the endocannabinoid system appears to be involved in the extinction of aversive memories, and both THC and CBD have been shown individually in separate studies to facilitate extinction of the conditioned fear response.13,14 Recent neuroimaging studies have found increased CB1 receptor availability in multiple brain regions in PTSD, including the amygdala-hippocampal-cortico-striatal circuit implicated in its pathophysiology.15
The National Academy report also found limited evidence of an association between cannabis use and increased severity of symptoms among individuals with PTSD, but the cause-and-effect relationships are unclear. Individuals with more severely symptomatic PTSD may be more likely to self-medicate with cannabis. The possibility of symptom exacerbation with cannabis use must be weighed against reported therapeutic benefit in individual cases. Other psychiatric diagnoses for which the National Academy report found limited evidence for effectiveness include Tourette syndrome and social anxiety disorders.
Cannabis and opioids
The National Academy report did not find evidence to support or refute the conclusion that cannabis or cannabinoids are effective in achieving abstinence from addictive substances. However, one study of molecular THC to decrease opioid withdrawal during acute detoxification and increase treatment retention with naltrexone found that patients who elected to continue smoking marijuana were more likely to complete treatment.16
On the issue of whether cannabis access might impact opioid use and related problems, other recent studies have found decreased mortality17 due to opioid narcotic overdoses and reductions in hospitalizations18 related to opioid dependence and opioid overdose in states that have passed medical cannabis laws. Another recently published analysis of data on 44,000 illicit opioid users who completed the National Survey on Drug Use and Health from 2007 to 2013 found that marijuana use was associated with a 55% reduced risk of past year opioid abuse.19
Dr. Fichtner reports no conflicts of interest concerning the subject matter of this article. Dr. Moss reports that he owns 24 common stock shares of GW Pharmaceuticals currently valued at $2900 in his IRA. GW Pharmaceuticals is the maker of the drugs Sativex and Epideolex.
Dr. Fichtner and Dr. Moss are Clinical Professors of Psychiatry at the University of California, Riverside School of Medicine.
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