Cannabis and Cannabis Use Disorder¶
Chapter 466 | Part 13: Neurologic Disorders
KEY CLINICAL POINTS¶
- Global cannabis use exceeds 150 million people; 42 million used marijuana in the last month (2023 NSDUH).
- D9THC acts as a partial agonist at CB1R and CB2R, modulating glutamatergic/GABAergic pathways.
- Cannabis Use Disorder (CUD) is defined by clinically significant impairment from problematic cannabis use.
- Adolescent cannabis use correlates with reduced prefrontal cortex thickness and cognitive deficits.
- EVALI (2019-2020) linked to vitamin E acetate in black-market e-liquids; no FDA-approved medications for CUD.
1. DEFINITION & OVERVIEW¶
Cannabis use disorder (CUD) is a problematic pattern of cannabis use leading to clinically significant impairment or distress, per DSM-5 criteria. Cannabis (marijuana) contains >0.3% D9THC by dry weight, while hemp contains ≤ 0.3% D9THC. Legal status varies by state/territory; 24 states permit adult nonmedicinal use, 38 states permit medicinal use.
D9THC Concentrations in Cannabis Products¶
| Product Type | D9THC Range (%) | Administration Route |
|---|---|---|
| Hemp | <0.3 | Oral, topical |
| Legal Dispensary Products | 20–30 | Inhalation |
| Vape Pens | 75 | Inhalation |
| Solid Extracts (e.g., Shatter) | 95 | Inhalation |
| Edibles | 5–20 | Oral |
Pharmacokinetic Phases of D9THC¶
| Phase | Timeframe | Characteristics |
|---|---|---|
| Alpha Phase | 0–10 min | Rapid absorption into lipophilic tissues; brain concentrations continue to rise despite falling plasma levels |
| Beta Phase | 1–2 h | Slower elimination; total pharmacodynamic effect lasts 4–8 h |
1.1 Pharmacologic Effects¶
D9THC enhances well-being, reduces stress, but high doses cause anxiety/paranoia. Acts on CB1R in brain regions regulating mood, reward, and stress. Minor cannabinoids (CBD) have limited clinical relevance at typical concentrations.
1.2 Pharmacokinetics¶
Smoked D9THC peaks in plasma 5–10 min post-inhalation, with alpha half-life ~6 min and beta half-life 1–2 h. Metabolized to 11-hydroxy-THC (active) and 11-COOH-THC (inactive). Urinalysis detects 11-COOH-THC for days in occasional users, weeks in frequent users.
2. EPIDEMIOLOGY¶
Global cannabis use >150 million people. 2023 NSDUH: 42 million used marijuana last month, 10 million 12–25-year-olds used monthly. 12 million used tobacco, 19 million used alcohol. Legal status: 24 states/territories permit adult nonmedicinal use; 38 states/territories permit medicinal use. Legal hemp production is federally permitted.
2.1 Risk Factors¶
Early initiation, high THC exposure, frequent use, genetic predisposition, and comorbid substance use disorders increase CUD risk. Adolescents are particularly vulnerable to cognitive and neurodevelopmental harms.
2.2 Demographics¶
12–25-year-olds: 10 million monthly marijuana users, 19 million monthly alcohol users. 12 million tobacco users. Higher prevalence in males; racial disparities in legal enforcement.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
D9THC modulates ECS (endocannabinoid system) by binding CB1R and CB2R. CB1R activation in VTA reduces GABAergic inhibition of dopaminergic neurons, enhancing reward. Chronic use leads to receptor downregulation and tolerance. ECS disruption during fetal development affects neuronal migration and connectivity.
3.1 Molecular Mechanisms¶
D9THC activates CB1R in prefrontal cortex (reduced inhibition) and amygdala (anxiolytic effects). Endocannabinoids (2-AG, anandamide) regulate synaptic plasticity. Chronic use causes receptor desensitization and altered neurotransmitter systems.
4. CLINICAL FEATURES¶
Acute effects: euphoria, impaired coordination, anxiety, tachycardia. Chronic use: cognitive deficits, memory impairment, reduced prefrontal cortex thickness. Withdrawal symptoms: insomnia, anxiety, depression, loss of appetite. Adverse effects: psychosis, cardiovascular risks, respiratory issues with smoking.
4.1 Adolescent Vulnerability¶
Early use correlates with lower IQ, academic underperformance, and structural brain changes (reduced connectivity, cortical thickness). ABCD study links adolescent cannabis use to episodic memory deficits.
4.2 Neuroimaging Findings¶
Reduced white matter integrity in fornix (emotion/memory processing). Increased intracranial volume with prenatal cannabis exposure. Altered brain connectivity patterns in chronic users.
5. DIFFERENTIAL DIAGNOSIS¶
Anxiety disorders, schizophrenia, depression, substance-induced psychosis, and other substance use disorders. Distinguish cannabis-induced psychosis from primary psychotic disorders using clinical history and exclusion criteria.
5.1 Psychotic Symptoms¶
Cannabis-induced psychosis typically resolves with abstinence, while primary schizophrenia persists. Hallucinations/paranoia may occur with high-dose D9THC use.
6. INVESTIGATIONS & DIAGNOSIS¶
Urinalysis detects 11-COOH-THC for days in occasional users. Blood tests measure plasma D9THC levels (but poor correlation with impairment). Imaging (MRI) assesses structural brain changes. DSM-5 criteria for CUD include: 1) impaired control, 2) social/role dysfunction, 3) tolerance, 4) withdrawal.
6.1 Diagnostic Criteria (DSM-5)¶
At least two of the following: 1) recurrent use despite harm, 2) cravings, 3) tolerance, 4) withdrawal, 5) failed obligations, 6) interpersonal problems, 7) reduced activities, 8) continued use despite physical/psychological problems.
7. MANAGEMENT & TREATMENT¶
No FDA-approved medications for CUD. Treatment focuses on behavioral interventions: contingency management, motivational enhancement, cognitive-behavioral therapy (CBT). Pharmacologic options (e.g., naltrexone) show limited efficacy. Vaping cessation programs emphasize dose control and harm reduction.
7.1 Behavioral Interventions¶
Contingency management: reward abstinence. Motivational enhancement: address ambivalence. CBT: challenge cannabis use as coping mechanism. Family-based interventions (e.g., Coping Power Program) effective in adolescents.
7.2 Pharmacologic Options¶
Naltrexone (opioid antagonist) may reduce cravings. CBD (nonintoxicating) shows promise for anxiety but lacks FDA approval. Antipsychotics for cannabis-induced psychosis (e.g., risperidone).
8. PROGNOSIS & COMPLICATIONS¶
Chronic use increases risk of addiction, cognitive deficits, and psychiatric comorbidities. Withdrawal symptoms resolve within 2 weeks. Long-term risks: respiratory disease, cardiovascular effects, and neurocognitive impairment. Prenatal exposure linked to fetal growth restriction and developmental delays.
8.1 Addiction Risk¶
10–15% of users develop dependence; higher in adolescents. Tolerance develops rapidly, with withdrawal symptoms peaking 1–3 days post-discontinuation.
9. SPECIAL CONSIDERATIONS¶
Pregnancy: maternal cannabis use linked to lower birth weight and preterm delivery. Adolescents: increased risk of academic decline and neurodevelopmental harm. Edibles pose overdose risk due to delayed onset and variable bioavailability. Vaping: potential for respiratory injury (EVALI) with vitamin E acetate exposure.
9.1 Pregnancy¶
American College of Obstetricians and Gynecologists advises against marijuana use during pregnancy. Prenatal cannabis exposure associated with altered brain connectivity and cognitive deficits.
9.2 Edibles & Dosing¶
Oral absorption delayed by first-pass metabolism (5–6% bioavailability). Fatty meals increase bioavailability 200–400%. Dosing unpredictability increases overdose risk.
10. KEY POINTS & CLINICAL PEARLS¶
- D9THC bioavailability varies by route: 30–35% smoked, 5–6% oral.
- Adolescents using cannabis >10 times/week show 30% reduced prefrontal cortex thickness.
- EVALI linked to vitamin E acetate in e-liquids; cessation of this agent reduced outbreaks.
- Contingency management and motivational enhancement are first-line treatments for CUD.
- No FDA-approved medications for CUD; naltrexone shows limited efficacy.