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DATE: May 30, 2019 Opioids and Other Drugs, Pain and Addiction Treatment Annual Meeting Bend, Oregon
The Health Effects of
Cannabis and Cannabinoids
Dennis McCarty, PhD
Professor Emeritus
OHSU-PSU School of Public Health
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Disclosures
• In the past three years, Dr. McCarty served as an
investigator on a study that received donated
medication from Alkermes (i.e. extended-release
naltrexone).
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Learning Objectives
• Enhance your comfort addressing patient questions
regarding medical use of cannabis
• Describe the quality of evidence for cannabis harms and
benefits
• Understand why cannabis research is limited
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National Academy of Medicine (2017)
• Sarah Feldstein Ewing, PhD OHSU School of Medicine Department of Psychiatry
• Committee Member• Committee updated the 1999
Institute of Medicine review Marijuana and Health
• https://www.nap.edu/catalog/24625/the-health-effects-of-cannabis-and-cannabinoids-the-current-state
• PDF can be downloaded at no cost
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Statement of Task: Committee Will• develop a consensus report assessing a) the health
effects of cannabis use and b) potential therapeutic uses
• provide an overview of the cannabinoid &
endocannabinoid system, history of use in the US, and
describe the regulatory and policy landscape.
• make recommendations for a research agenda.
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Weight of Evidence Categories
• Conclusive: strong evidence from randomized trials
• Substantial: supportive findings from good-quality studies with few
credible opposing findings
• Moderate: some evidence from good to fair-quality studies with
few credible opposing findings
• Limited: weak evidence from fair quality studies with mixed findings
• Insufficient: insufficient evidence from mixed findings or a single
study
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Areas reviewed• Therapeutic effects
• Cancer
• Cardiometabolic risk
• Respiratory disease
• Immunity
• Injury and death
• Prenatal and neonatal exposure
• Psychosocial
• Mental health
• Problem cannabis use
• Abuse of other substances
• Challenges and barriers in cannabis and cannabinoid research
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Conclusions: Substantial Evidence
• Substantial evidence that cannabis is effective for
– Treatment of chronic pain and as anti-emetics
– Improving Multiple Sclerosis spasticity symptoms
• Substantial evidence that use
– Increases risk of motor vehicle crashes
and schizophrenia
– While pregnant reduces fetal birth weight
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Conclusions: Therapeutic Effects• Moderate evidence that cannabis is effective for improving
short-term sleep outcomes for
– Obstructive sleep apnea, Fibromyalgia, Chronic pain,
Multiple Sclerosis
• Limited evidence that cannabis is effective for improved
– appetite and reduced weight loss in HIV, measures of MS
spasticity, Tourette symptoms, anxiety, PTSD
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Conclusions: Therapeutic Effects
• Limited evidence of improved outcomes for TBI
• Limited evidence that cannabis is ineffective for
reducing symptoms of
– dementia & glaucoma
– depression associated with chronic pain or MS
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Conclusions: Therapeutic Effects
• Insufficient evidence that cannabis is effective for
– Cancers, IBD, Epilepsy,
Paralysis spasticity, ALS,
Huntington’s disease, Parkinson’s disease,
Dystonia, Achieving abstinence for SUD
Mental health outcomes for schizophrenia
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Conclusions: Cancer
• Moderate evidence of no statistical association with
– Lung cancer from cannabis smoking
– Head and neck cancer
• Limited evidence of a statistical association with
– Testicular germ cell tumors from frequent use
• Insufficient evidence to support a statistical assoc with
esophageal, prostate, cervical, anal and bladder cancers
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Conclusions: Cardiometabolic risk
• Limited evidence of a statistical association with
– Triggering myocardial infarction, ischemic stroke,
decreased risk of metabolic syndrome and diabetes
• No evidence of association between chronic use and
– Increased risk of acute myocardial infarction
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Conclusions: Respiratory Disease• No evidence of an association with worse respiratory symptoms and
more bronchitis episodes
• Moderate evidence of improved airway dynamics with acute use but
not chronic use
• Moderate evidence of improved respiratory symptoms when cannabis
use stops
• Limited evidence of increased risk of COPD
• No evidence of an association with increased hospital admits for COPD
and development or exacerbation of Asthma
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Conclusions: Immunity
• Limited evidence of associations of cannabis smoking
with a decrease in inflammatory cytokines
• Limited evidence of no association of daily cannabis use
with progression of liver fibrosis or hepatic disease in
individuals with HCV
• No evidence of an association with adverse immune cell
response in healthy individuals or with HIV or HPV
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Conclusions: Injury and Death
• Substantial evidence of risk of motor vehicle crashes
• Moderate evidence of risk of overdose and respiratory
problems in pediatric populations in states w/legal use
• No evidence of an association with all cause mortality,
occupational injury, or death due to cannabis overdose
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Conclusions: Prenatal exposure
• Substantial evidence of maternal use & low birth weight
• Limited evidence of maternal use and pregnancy
complications or admission to neonatal intensive care
• No evidence of delayed outcomes in development and
maturation.
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Conclusions: Psychosocial
• Moderate evidence of association with impaired cognition
from acute use.
• Limited evidence of association with impaired academic
achievement, unemployment, social functioning
• Limited evidence of sustained abstinence and impaired
cognitive function.
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Conclusions: Mental Health
• Substantial evidence of elevated risk of schizophrenia
(highest risk among most frequent users)
• Moderate evidence of improved cognitive performance
in people with psychotic disorders, increased mania and
hypomania in people with bipolar disorders, increased
risk of depression, suicidal ideation, suicide completion,
and increased social anxiety disorder
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Conclusions: Mental Health
• Moderate evidence of no association with more
negative symptoms of schizophrenia
• Limited evidence of increased positive symptoms of
schizophrenia, development of bipolar disorder, anxiety
disorder, symptoms of anxiety, or more severe PTSD
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Barriers to Research
• Classification as Schedule I impedes research
• Difficult to access the quantity, quality and type of
cannabis product for research on health effects of use
• A diverse network of funding sources is required
• Improved and standardization of research methods is
required to develop conclusion evidence of positive and
negative health effects.
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Research Recommendation 1
• Develop an evidence base on the short-term and long-
term health effects of cannabis use
– Clinical and observational research
– Health policy and economics research
– Public health and public safety research
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Research Recommendation 2
• Promote development of research standards to improve
the quality of cannabis research
– An observational and clinical study minimum dataset
– Uniform terminology for cannabis research
– Standardized question banks for clinical research
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Research Recommendation 3
• Improve surveillance capacity
– Develop question banks on beneficial and harmful
effects of cannabis use for use in national surveys
– Assess use of diagnostic codes to monitor health
effects
– Establish standards for testing facilities
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Research Recommendation 4
• Address research barriers
– Expand access to research-grade marijuana
– Develop nontraditional funding to support research
– Improve the quality, diversity and validity of
research-grade cannabis products
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Cannabis, opioids and
ecological validity• Studies of opioid mortality suggest reduced death rates in
states with medical cannabis (Bachhuber et al, JAMA IM,
2014, 174, 1668 – 1673; Powell et al, Rand working papers)
• A longitudinal study, however, found cannabis use was
associated with increased risk of opioid use initiation and
greater risk of developing an opioid use disorder with
increasing levels of cannabis use (Olfson et al Am. J. of
Psychiatry, 2018, 175, 47 – 53)
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Thank You