THC is associated with a relatively high risk of side effects that tend to be dose-dependent (occurring more often with increasing doses).
The most common side effects of THC include sedation, dizziness, confusion, impaired cognition, impaired coordination, euphoria, anxiety, paranoia, heightened sensory awareness, headache, dry mouth, increased appetite, and nausea. THC can cause intoxication and impair the ability to drive.[1][3][4]
Less often, THC may cause vomiting, hallucinations, increased heart rate, orthostatic hypotension, and psychosis (in predisposed individuals).[1] There have also been case reports linking THC with an increased risk of seizure or heart attack.[5][6][7]
If THC is inhaled via smoking or vaping, it can increase the risk of lung disease or lung injury. Vaporizing THC can minimize the production of potentially cancer-causing compounds formed through combustion; however, there is still a risk of lung injury with vaping.[2]