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Medical Cannabis: Legal Status, Therapeutic Uses, Risks & Clinical Guidance

Medical cannabis refers to regulated cannabis products prescribed for specific medical conditions. Distinct from recreational use, it involves standardized cannabinoid content (THC, CBD), quality control, and clinician oversight.

Legal Landscape (US Focus)

Federal: Schedule I (illegal); Rohrabacher-Farr amendment limits DOJ enforcement against state-compliant programs
State: 38 states + DC have comprehensive medical programs; 12 allow only low-THC/CBD
Requirements: Qualifying condition, clinician certification, state registration, licensed dispensary purchase
Employment/Driving: No federal protection; state laws vary; DUI laws apply (per se THC limits in some states)

Qualifying Conditions (Common Across States)

Chronic pain (neuropathic, cancer, central sensitization)
Chemotherapy-induced nausea/vomiting (CINV)
Multiple sclerosis spasticity
Epilepsy (especially Dravet, Lennox-Gastaut — CBD-dominant)
PTSD (many states)
HIV/AIDS wasting, Crohn's, ALS, Parkinson's, glaucoma, terminal illness

Cannabinoid Pharmacology

Compound	Receptor Action	Primary Effects
THC (Δ⁹-tetrahydrocannabinol)	CB1 (CNS) partial agonist, CB2 partial agonist	Analgesia, antiemesis, appetite stimulation, psychoactivity, anxiolysis/anxiety (biphasic)
CBD (cannabidiol)	Low CB1/CB2 affinity; multiple non-cannabinoid targets (5-HT1A, TRPV1, GPR55)	Anticonvulsant, anxiolytic, anti-inflammatory, antipsychotic, non-intoxicating
THC:CBD balanced	Entourage effect	Improved therapeutic index vs. THC alone

Formulations & Routes

Inhalation (vaporization — not combustion): Rapid onset (min), short duration (2–4 hr); titration control
Oral (oils, capsules, edibles): Slow onset (1–3 hr), long duration (6–12 hr); high variability, first-pass metabolism → 11-OH-THC (more psychoactive)
Sublingual/oromucosal: Intermediate onset (15–45 min), bypasses first-pass
Topical: Local effects (pain, inflammation); minimal systemic absorption
Rectal/vaginal: Alternative for GI intolerance

Evidence-Based Indications (NASEM 2017 + Updates)

Substantial evidence: Chronic pain (cannabis), CINV (oral cannabinoids), MS spasticity (nabiximols)
Moderate evidence: Sleep improvement (disturbed sleep), PTSD (limited), Tourette's
Limited/insufficient: Most other conditions (anxiety, depression, IBD, glaucoma, dementia)
FDA-approved: Epidiolex (CBD) for Dravet/LGS/TSC; Marinol/Syndros (dronabinol) for CINV, AIDS anorexia; Cesamet (nabilone) for CINV

Risks & Contraindications

Risk	Population/Context	Mitigation
Cognitive impairment	Acute: attention, memory, psychomotor; Chronic: possible IQ decline if adolescent onset	Low THC, CBD-rich; avoid driving/operating machinery
Psychiatric	Anxiety, paranoia, psychosis (THC); cannabis use disorder (~10% users)	Screen for personal/family hx psychosis; avoid high THC
Respiratory	Smoking → bronchitis; vaping → EVALI risk (illicit carts)	Vaporize flower or use non-inhaled routes
Cardiovascular	Tachycardia, orthostatic hypotension, MI risk (acute)	Caution in CAD, arrhythmia
Pregnancy/lactation	Neurodevelopmental risks; THC in breast milk	Avoid
Drug interactions	CYP3A4/2C9/2C19 substrates (warfarin, clobazam, tacrolimus, etc.)	Review meds; dose adjust; monitor levels

Clinical Best Practices

Confirm diagnosis, document failed conventional therapies
Assess contraindications, risk factors (CAGE-AID, PHQ-9, GAD-7)
Start low, go slow: CBD-dominant or balanced ratio; titrate THC cautiously
Set functional goals (pain interference, sleep quality, spasticity score)
Follow-up q4–12 weeks: efficacy, adverse effects, misuse screening
Document in EMR; coordinate with other prescribers

Medical cannabis is a therapeutic tool—not a panacea. Evidence supports specific indications; risks require informed consent and ongoing monitoring. Clinicians should stay current with evolving state laws and cannabinoid science.