The acute effects of cannabis administration in humans are diverse and impact various physiological systems. A notable and consistent response is tachycardia, which, alongside peripheral vasodilation, can increase the risk of myocardial infarction (MI) shortly after use. Studies have indicated a heightened risk of MI within the first hour following cannabis consumption, emphasizing the cardiovascular risks associated with acute use. These effects appear to be more pronounced in individuals who are not chronic users, suggesting a potential tolerance development over time.
Cannabis also has significant respiratory effects, notably bronchodilation and decreased airway resistance, which can paradoxically coexist with airway hyperreactivity similar to that observed in tobacco smokers. This duality can lead to concerns, especially in the perioperative setting, where acute inhalation prior to surgery might increase the risk of airway complications.
Psychiatric responses to cannabis vary widely among users. While some report reduced anxiety, others experience exacerbated anxiety, paranoia, or even psychosis, particularly with high doses of THC. The risk of psychotic episodes correlates with the frequency of use, raising concerns about the psychiatric safety of cannabis, especially in individuals with a personal or family history of psychosis.
Cannabinoid hyperemesis syndrome, characterized by recurrent episodes of severe nausea and vomiting, represents another distressing adverse effect. The syndrome's etiology remains poorly understood, but it underscores the complex impact of cannabinoids on gastrointestinal function.
The psychomotor effects of cannabis contribute to its association with increased risks of motor vehicle accidents, highlighting impaired reaction times and coordination. Additionally, acute cannabis intoxication can lead to various other health complications, including severe bleeding linked to the use of non-FDA-approved synthetic cannabinoids and burns from the production of cannabis extract products. Additional, though less severe, acute symptoms of cannabis use encompass dry mouth, headaches, dizziness, impaired memory, abdominal discomfort, and heightened hunger. These acute effects, ranging from cardiovascular and respiratory complications to psychiatric and gastrointestinal disturbances, illustrate the broad and impactful nature of cannabis on human physiology and the need for awareness and caution in its use.
| System | Acute effects | Clinical relevance |
|---|---|---|
| Cardiovascular | Tachycardia with peripheral vasodilation | Heightened risk of myocardial infarction within the first hour after use |
| Respiratory | Bronchodilation and decreased airway resistance coexisting with airway hyperreactivity similar to tobacco smokers | Acute inhalation before surgery may increase the risk of airway complications |
| Psychiatric | Reduced anxiety in some users; exacerbated anxiety, paranoia, or psychosis in others, particularly with high THC doses | Risk of psychotic episodes correlates with frequency of use; greater concern with personal or family history of psychosis |
| Gastrointestinal | Cannabinoid hyperemesis syndrome — recurrent episodes of severe nausea and vomiting, with an etiology that remains poorly understood; abdominal discomfort; increased hunger | — |
| Neurologic / psychomotor | Impaired reaction time and coordination, impaired memory, dizziness, headache | Associated with increased risk of motor vehicle accidents |
| Other | Dry mouth; severe bleeding linked to non-FDA-approved synthetic cannabinoids; burns from production of cannabis extract products | — |
