“Greening out” is a colloquial term describing an acute, adverse physical and psychological reaction following the consumption of too much cannabis, particularly products high in delta-9-tetrahydrocannabinol (THC). While generally temporary and not fatal, the experience can be extremely distressing and unpleasant. It represents a form of overwhelming intoxication from overconsumption.
Defining the Experience and Recognizing Symptoms
The experience is characterized by a rapid onset of both physical discomfort and intense psychological distress, signaling the body’s negative reaction to an overwhelming dose of THC. Physical signs often begin with severe nausea, which may progress to vomiting as the body attempts to expel the excess substance. Affected individuals may become noticeably pale and experience profuse sweating or chills.
Common physical manifestations include feeling dizzy or lightheaded, often accompanied by a rapid heart rate (tachycardia). Some people also report physical immobility or a lack of coordination, making it difficult to stand or move. These effects indicate that the dosage has pushed the body past its comfort level.
Simultaneously, the psychological symptoms can be profoundly disturbing. Intense paranoia is frequently reported, where feelings of unease escalate into fear or mistrust of the surroundings and others. This can quickly spiral into severe anxiety or panic attacks, marked by an overwhelming sense of dread. The person may also feel disoriented, struggle to focus, or experience an altered sense of time.
The Physiological Mechanics of Greening Out
The unpleasant experience of greening out is rooted in how high concentrations of THC interact with the body’s endocannabinoid system (ECS). THC acts as an agonist, meaning it binds to and activates cannabinoid receptor type 1 (CB1) receptors, which are highly abundant throughout the brain and nervous system. When the dose is too high, this interaction overstimulates the ECS, leading to the adverse effects.
One primary mechanism is the effect on the cardiovascular system, resulting in orthostatic hypotension—a sudden drop in blood pressure upon standing. THC causes vasodilation (the widening of blood vessels), which lowers overall blood pressure. This sudden pressure drop means less blood reaches the brain, triggering dizziness, lightheadedness, and sometimes fainting.
Intense nausea and vomiting are caused by THC’s interaction with CB1 receptors in the brain stem, which regulates these involuntary functions. While low doses of cannabis can act as an anti-nausea agent, an excessive dose overwhelms the system, paradoxically causing the opposite effect. Psychological symptoms, such as anxiety and paranoia, stem from the overstimulation of CB1 receptors in the amygdala and other brain areas governing emotional regulation and fear responses.
A contributing factor can be a temporary drop in blood sugar levels (hypoglycemia), which exacerbates feelings of lightheadedness and physical discomfort. When the system is flooded with THC, the coordinated signaling of the ECS is disrupted, resulting in a cascade of physical and mental distress. The duration of these effects is determined by how quickly the body can metabolize and process the excessive concentration of THC.
What to Do During and After the Episode
The first step during an episode is to immediately stop consuming cannabis and move to a safe, calm environment. Finding a quiet room with dim lighting helps reduce sensory input that often worsens anxiety and disorientation. If dizziness is present, it is safest to lie down to mitigate the effects of the blood pressure drop and prevent accidental injury.
Managing psychological distress involves focusing on slow, deep breathing, which helps calm the nervous system and reduce a rapid heart rate. Staying hydrated is important; slowly sipping water can help with dry mouth and may mitigate nausea and dehydration. If possible, a light snack containing carbohydrates can help stabilize blood sugar levels.
Recovery requires supportive care while the body processes the THC, which can take a few hours, or longer if edibles were consumed. The person should remain in a secure place with a trusted individual until symptoms substantially subside. Seek immediate medical attention by calling emergency services if the person experiences sustained loss of consciousness, severe chest pain, difficulty breathing, or uncontrollable and persistent vomiting.