Cannabis and Special Risk Populations
Cannabis may not be suitable for all patients
Cannabis and Special Risk Populations
Cannabis may not be suitable for all patients
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Several publications from Health Canada, the CFPC, and others, have identified a set of special-risk populations in the context of both medical and recreational cannabis use. 1,2,3,4,5,6,7,8 More Level 1 research is needed on both the therapeutic and adverse effects of cannabis for specific presentations and populations.

This resource provides an overview of the risks of cannabis use in the following commonly-cited populations:

  • Women who are pregnant, breastfeeding, or planning to become pregnant
  • Children and youth under 25 years
  • Individuals with current, past, or family history of psychosis
  • Individuals with current, past, or family history of substance use disorder

This resource also includes a note on cannabis use and the increased risk of psychosis and psychotic disorder in the general population.

Pregnant women and fetuses
    • If a woman consumes cannabis while pregnant, she will expose the fetus to delta-9-tetrahydrocannabinol (THC) — the primary psychoactive component in cannabis — through her bloodstream.6,9
    • A 2016 systematic review and meta-analysis of evidence shows that fetuses exposed to THC are more likely to experience lower birth weight and higher odds of placement in NICU/ICU.10
    • A recent large retrospective study found a significant association between cannabis use during pregnancy and increased risk of preterm birth. After controlling for poly-substance use, the study found that women who reported use of cannabis alone during pregnancy showed a 1.34-fold risk of preterm birth when compared to women who reported no use of substances during pregnancy.11
    • Studies to date suggest that women who consume cannabis during pregnancy may have a greater risk of anemia.10
    • Acute effects of cannabis consumption include a decrease in blood pressure, which may increase the risk of falls causing injury to both mother and fetus. 6
    • Findings from two prospective longitudinal cohort studies show that heavy in utero exposure (at least 5 times per week) to THC can negatively effect children’s neurocognitive development. 9,12,13 These effects include, but are not limited to:
      • hyperactivity
      • deficits in memory, verbal and visual reasoning, verbal skills
      • reduced academic achievement
    • There is increasing evidence to support a link between maternal cannabis use in pregnancy and the subsequent initiation and frequency of substance use by children in adolescence.9
    • Studies point to higher instances of negative effects on the fetus when cannabis and tobacco use are combined during pregnancy (compared to either cannabis or tobacco alone).9,14,15

Note: Many of the studies of cannabis use during pregnancy consider only one method of cannabis consumption and also have one or more of the following limitations:

  • Not controlled for concurrent use of tobacco and/or alcohol
  • Reliant on self-reported data
  • Cannabis products used are not standard (THC levels vary)
Breastfeeding women
  • THC is stored in fatty tissues and accumulates in breast milk. Recent studies have shown that the THC in breast milk is subsequently metabolized by breastfeeding babies. 6,9,16
  • Several reports indicate that babies exposed to THC in breast milk may experience negative short-term effects, including: 16,17
    • lethargy
    • reduced muscle tone
    • poor feeding habits
Women attempting to conceive
  • There is limited evidence that suggests cannabis consumption may negatively impact a woman’s ability to conceive by: 17,18,19,20
    • disrupting hormonal regulation and menstrual cycles
    • reducing movement of ova through the oviducts
    • decreasing success of in vitro fertilization.
Under the age of 25
  • The human brain continues to develop until the age of 25. Multiple sources have established that regular cannabis use during adolescence and early adulthood can cause functional and structural changes to the brain, impairing its development. 2, 7, 22, 23, 24, 25
  • Cannabis is not appropriate for medical use in pediatric populations except in very specific circumstances, including certain forms of refractory epilepsy (e.g., Dravet syndrome). 26
  • Cannabis use during adolescence has been associated with:
    • increased risk of cannabis use disorder (approximately one in six) 27, 28
    • increased risk of developing mental health problems, including anxiety, depression, suicidal thoughts or attempts, psychosis, and schizophrenia 22, 29, 30, 31, 32, 33 34 35
    • increased risk of cognitive deficits and poorer school performance 22, 36, 37
  • Cannabis use has been shown to trigger or amplify a genetic predisposition to psychotic disorders. 8, 38, 39
  • For individuals with a first-degree relative who has a history of psychosis, consuming cannabis on a daily basis could increase the risk of developing a psychotic disorder by up to ten times compared to non-users with a family history of psychosis. 8, 39
  • Of individuals who are treated for psychosis, those who began using cannabis during adolescence and early adulthood experience their first psychotic episode three to six years earlier than those who have never used cannabis. 8, 40, 41
Note on cannabis use and the increased risk of psychosis and psychotic disorder in the general population
  • Cannabis use increases the risk of psychosis and psychotic disorders in all users (not just those with a predisposition to psychosis or psychotic disorders).8, 22, 39, 42, 43
  • Individuals who have used cannabis in their lifetime have a 40% higher risk of developing a psychotic outcome than those who have not used cannabis. 8, 39
Risk Factors for the General Population
Use in Adolescence
  • Individuals who begin using cannabis before the age of 16 have a higher risk of developing psychosis and higher odds of developing a psychotic disorder compared to those who started cannabis use later, or who never used cannabis.7, 44, 45
  • More than 50% of youth who develop psychotic symptoms from cannabis use will develop a future psychotic disorder.33
Frequent Use
  • There is a direct relationship between frequent cannabis use and the risk of developing psychosis.8, 39, 45, 46
  • Individuals who use cannabis daily are up to three times more likely to be at risk of developing psychotic disorders than those who do not use cannabis.8,45
High THC Potency
  • Individuals who use cannabis products with high-potency THC (>10%) are at a greater risk of experiencing a psychotic episode and a greater risk of developing a psychotic disorder when compared to non-users and cannabis users who consume lower THC products. 45, 48
Combined Risks
  • Potency and frequency: Individuals who consume high-potency THC (>10%) cannabis on a daily basis are almost five times more likely to develop a psychiatric disorder compared to non-users.48
  • Potency and age: Individuals who begin using high-potency THC (>10%) cannabis before the age of 16 are two times more likely to develop a psychiatric disorder compared to non-users.48
  • Cannabis can be an addictive substance, and the risk of developing cannabis use disorder is higher for individuals with a current, past, or family history of substance use disorder. 2,49
  • Daily cannabis use, prolonged cannabis use, and cannabis use during adolescence can all further increase the risk of cannabis use disorder. 2, 49

Cannabis is made up of many different cannabinoids. Individual cannabinoids may not all share the same potential for abuse.

  • Delta-9-tetrahydrocannabinol (THC) and Cannabidiol (CBD) are the two main components in cannabis.
    • THC is the primary psychoactive compound in cannabis. It is responsible for both the “high” and the impairments associated with cannabis use. 50
    • CBD, which is commonly isolated for therapeutic uses, does not produce psychoactive or intoxicating effects. 50
  • According to the WHO Expert Committee on Drug Dependence, CBD has a low likelihood of abuse. 51
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Updated: October 15, 2019