Most people who have smoked cannabis have experienced the so-called “bad trip” at some point in their lives. Many of these trips have occurred after a particularly heavy dose of THC in one sitting. I myself had this experience with the delayed-onset of edibles, thinking to myself that since I hadn’t felt anything yet, I obviously should just eat more. Bad mistake.
Bad trips can be scary. They are often associated with episodes of paranoia, panic attacks, and dizziness.  Even depersonalization events and hallucinations more commonly associated with more potent hallucinogenic substances like psilocybin (‘magic mushrooms’) or LSD (‘acid’)have been reported in conjunction with heavy cannabis use.
A similar mechanism of action between all three responses has been proposed, though it has not been thoroughly tested.  However, recent literature reports qualitative differences in the hallucinations between the different substances that may be attributable to different pharmacological mechanisms of actions. 
One method known to reduce both the likelihood of experiencing a bad trip and the intensity of the “badness” is using cannabis products that have a relatively high concentration of CBD, or to take CBD prophylactically before or after acute THC ingestion.  CBD has previously been shown to modulate the negative psychological effects of its psychoactive cannabinoid cousin. 
As I experienced before, bad trips can be caused by an acute “over”-dose of THC. These events are temporary—which is often the best thing to tell someone who may be experiencing them at the time. Time does become dilated when you are high, which may feel like you are overly high for much longer than you actually are. However, reassuring the person that the feeling will pass is the most likely way to help someone get over an acute bad trip.
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