The American Society of Addiction Medicine - Public Policy Statement on Cannabis: 2020
Following is an excerpt
Cannabis & Medical Purposes – The Evidence
Cannabis use has been shown to be associated with cognitive decline, impaired education or occupational attainment, risk of other substance use disorders, and poor quality of life.10 It has also been shown to be associated with impaired driving and fatal vehicle crashes, cannabis-related emergency room visits, psychosis, and psychiatric comorbidity.11 CUD has been associated with disability11 and strongly and consistently associated with other substance use and mental disordres.10 Use of high potency cannabis has been associated with increased frequency of use, cannabis use-related problems and increased likelihood of anxiety disorder.12
In 2013-2014, 9.8% of U.S. adults who used cannabis in the past year reported doing so for medical purposes, and 21.2% of adults who reported using cannabis for medical purposes resided in states that had not legalized cannabis use for such purposes.15 Over 75% of those who use cannabis for medical purposes also report using it for non-medical purposes.16
States have approved various indications for cannabis use, despite a lack of sufficient scientific evidence for its effectiveness as a medicine for many of these indications. A 2017 review by the National Academies of Sciences, Engineering, and Medicine found conclusive or substantial evidence that cannabinoids are effective in only three conditions: chemotherapy-induced nausea and vomiting, multiple sclerosis-related spasticity, and chronic pain.17 According to a Cochrane review, the effectiveness of cannabis-based medicines for neuropathic pain was small and may be outweighed by potential harms.18 A systematic review of 43 randomized controlled trials found that cannabis-based medicine might be effective for chronic pain based on limited evidence, primarily for neuropathic pain, and that, due to small effect sizes, the clinical significance is uncertain.19
Although some states include mental health disorders as indications for cannabis for medical purposes, cannabis use may be particularly harmful to populations with or at risk for mental health disorders. A 2019 meta-analysis of 83 studies reported scarce evidence that cannabis or any type or formulation of medicinal cannabinoids improve depressive disorders, anxiety disorders, attention-deficit hyperactivity disorder, Tourette syndrome, post-traumatic stress disorder (PTSD), or psychosis.20 In 2019 the American Psychiatric Association stated that “there is no current scientific evidence that cannabis is in any way beneficial for the treatment of any psychiatric disorder. Current evidence supports, at minimum, a strong association of cannabis use with the onset of psychiatric disorders.”21 Cannabis has been shown to contribute to risk factors for the onset and symptom severity of substance-induced psychosis and bipolar disorder as well as the onset of depression and anxiety disorders; there is preliminary evidence that ongoing cannabis use in persons with a history of trauma increases the odds of developing PTSD.22
A widely publicized study found lower opioid overdose rates in states that legalized cannabis use for medical purposes compared with other states through 2010.23 This led some states to include opioid use disorder (OUD) as a possible indication for cannabis used for medical purposes.24 However, a subsequent analysis extended through 2017 and using similar methods with additional controls found the opposite association.25 Studies of individuals show an association between cannabis use and increased rates of non-medical opioid use and OUD.26 There is no current evidence that cannabis is effective for the treatment of OUD.27 Further, due to its mechanism of action, cannabis would not be expected to reduce opioid overdose rates, unlike the existing FDA-approved medications for OUD. There has been a preliminary finding of an effect of CBD in reducing opioid cue-induced craving,28 but this requires further research to assess the clinical significance.
