The Role of Cannabis in Treating Anxiety: An Update

Michael Van Ameringen; Jasmine Zhang; Beth Patterson; Jasmine Turna

Disclosures

Curr Opin Psychiatry. 2019;33(1):1-7. 

In This Article

Cannabis in Clinical Trials

Despite the potential anxiolytic effects of cannabis constituents observed in animal models, results from clinical trials in humans have been largely inconclusive. Critically, prospective examinations of the cannabis plant in anxiety disordered population simply do not exist; however, a small literature examining cannabis-related compounds has been noted.[18–20] Nabilone, a synthetic cannabinoid, was found to be effective for reducing anxiety in both an open-label and a double-blind study.[21] However, a single-dose of 1–5 mg nabilone was ineffective for four anxious volunteer individuals.[22] More recently, a study of nabilone in patients taking antidepressant medications for mixed anxiety and mood disorders showed significant improvements in anxiety scores,[23] and anxiolytic effects were also observed in a more recent randomized, placebo-controlled (RCT) four-dose trial in patients with GAD.[24]

CBD has also been studied in a recent RCT in social anxiety disorder, in which 57 healthy males received a single-dose of oral CBD (150, 300, or 600 mg) or placebo.[25] Following CBD administration, individuals completed a simulated public speaking test during which anxiety levels were assessed using a Subjective Visual Analogue Mood Scale. Compared to placebo, those who received 300 mg CBD 90 min prior to the public speaking task had significantly lower ratings of social anxiety (P = 0.042); whereas 150 and 600 mg CBD did not produce any detectable benefits. In a larger retrospective case series, adults with primary anxiety symptoms (N = 72) consumed 25 mg/day of CBD for 3 months.[26] One month following study initiation, 79.2% of patients reported experiencing improvements in symptoms as indicated by lower scored on the Hamilton Anxiety Rating Scale; this percentage remained relatively stable at three months. Although these results support a therapeutic effect of CBD in treating anxiety-related disorders, this study lacked a control condition. The authors also noted that patients in their clinic often expressed a desire to reduce or to avoid the use of psychiatric medications which may have exaggerated bias and a placebo effect as they received a desirable 'alternative' treatment.[26]

Evidence for cannabis in anxiety can also be drawn from studies where it has been assessed as a secondary outcome, including two clinical trials investigating the efficacy of long-term use of cannabis or related compounds for other health conditions. A prospective open-label study assessed the effect of a cannabis herbal tea on pain-related symptoms, anxiety, and depression in patients (N = 338) with chronic pain for 12 months.[27] At the 3-month assessment point, patients reported significant improvements in anxiety as shown by a 3-point decrease the Hospital Anxiety and Depression Scale, which were maintained at endpoint. However, results differed in a recent pilot RCT of 18 patients with cannabis dependence. Patients who received either daily 2 mg nabilone or placebo for 10 weeks, did not produce significant between-group differences in anxiety symptoms at study endpoint from baseline, as measured by the Beck Anxiety Inventory.[28]

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