What are the effects of marijuana on the body?

Effects of Marijuana on the Body

Marijuana use can cause significant cardiovascular risks including tachycardia, blood pressure changes, and increased risk of adverse cardiovascular events such as myocardial infarction and stroke, while also potentially affecting multiple body systems with both therapeutic and harmful effects depending on dose, frequency, and individual factors. 1

Neurological and Psychological Effects

• Acute effects:

  • Psychoactive effects primarily due to THC (delta-9-tetrahydrocannabinol)
  • Dizziness, drowsiness, and impaired coordination 2
  • Anxiety, suicidal ideations, and psychotic symptoms in vulnerable individuals 3
  • Impaired cognition and performance 3
  • Risk of psychosis is convincingly demonstrated in observational studies (OR 1.71) 4

• Chronic effects:

  • Neurocognitive impairments with prolonged use 3
  • Exacerbation of psychotic disorders in vulnerable people 3
  • Mood disorders and cannabis use disorders 3
  • Withdrawal syndrome with heavy chronic use 3

Cardiovascular Effects

• Increased heart rate (tachycardia) and blood pressure changes 1
• Orthostatic hypotension, particularly with heavy acute and chronic use 1
• Greater incidence of myocardial ischemia in at-risk individuals 1
• Increased stroke risk in a dose-dependent manner, with more frequent than once-weekly use associated with elevated stroke/TIA risk 1
• Increased risk of motor vehicle crashes, especially fatal collisions 3

Gastrointestinal Effects

• Cannabis hyperemesis syndrome - characterized by cyclic vomiting 3
• Nausea, vomiting, and increased thirst 2
• Appetite stimulation (therapeutic effect in certain conditions) 2

Therapeutic Applications

• Pain management:

  • Cannabis-based medicines can reduce chronic pain by 30% (OR 0.59) with high-grade evidence 4
  • Particularly effective for cancer and multiple sclerosis-associated pain 2

• Epilepsy:

  • Cannabidiol (CBD) improves 50% reduction of seizures (OR 0.59) with high-grade evidence 4
  • Reduces seizure events but may increase risk of pneumonia, gastrointestinal adverse events, and somnolence 4

• Multiple sclerosis:

  • Improves spasticity and pain with moderate-grade evidence 4
  • Increases risk of dizziness, dry mouth, nausea, and somnolence 4

• Cancer-related symptoms:

  • Anti-emesis in cancer patients 2
  • Improved sleep disruption but with gastrointestinal adverse events 4

Important Considerations and Precautions

• Dosing and administration:

  • THC daily dose should generally be limited to 30mg/day or less to avoid psychoactive sequelae and tolerance development 5
  • CBD requires higher doses for benefits on pain, inflammation, and attenuation of THC-associated anxiety 5
  • Dose initiation should start at modest levels with slow titration over up to two weeks 5

• High-risk populations:

  • Adolescents and young adults (18-25 years)
  • Adults over 65 years
  • Children (can cause serious adverse effects including stupor, lethargy, seizures, and coma) 2
  • Pregnant women (convincing evidence of increased risk for small gestational age [OR 1.61] and low birth weight [OR 1.43]) 4
  • Individuals with or prone to mental health disorders 4
  • Drivers (convincing evidence of increased car crash risk [OR 1.27]) 4

• Cannabis potency considerations:

  • Average THC concentration has increased from 9% in 2008 to 17% in 2017 1
  • Cannabis concentrates can have THC levels up to 70%, with higher potency associated with greater risk of adverse effects 1

Clinical Recommendations for Healthcare Providers

• Screen for cannabis use patterns and frequency in patients with cardiovascular risk factors 1
• Consider screening for cannabis use disorder in patients reporting sleep issues 1
• Advise patients about the cardiovascular risks of THC concentrate use 1
• Caution against combining THC with sedative medications or other substances that affect heart rate or blood pressure 1
• For patients using cannabis medicinally, oral administration (edibles) is generally preferred over smoking or vaping 6
• Advise patients that cannabis can make driving dangerous, recommending waiting 5-8 hours after use before driving 6

Cannabis use carries both potential therapeutic benefits and significant risks that must be carefully weighed based on individual patient factors, medical conditions, and treatment goals.