Cannabis green-out — first aid

TL;DR

• No lethal risk from THC alone (theoretical lethal dose >15 g pure THC).
• Symptoms: tachycardia, nausea, anxiety, vomiting, dissociation — max 2–4 h.
• Calm environment, lie down, water, optionally sugar (blood pressure).
• CBD (30–50 mg oral) can blunt THC-induced anxiety (Bhattacharyya 2010, Arch Gen Psych).

When to call 144

• Prolonged loss of consciousness.
• Seizures.
• Persistent vomiting with aspiration risk.
• Chest pain or breathlessness in cardiac patients.
• For children: always call immediately.

Physiological mechanisms and risk factors

The occurrence of a so-called green-out is based on the intense interaction of tetrahydrocannabinol with the body's own endocannabinoid system. With a high intake, the CB1 receptors in the brain and cardiovascular system in particular are overactivated. This leads to a temporary dilation of the blood vessels, which can result in a rapid drop in blood pressure. To compensate for this drop, the body reacts with a reflex increase in heart rate. This interaction of low blood pressure and a rapid pulse triggers typical symptoms such as dizziness, cold sweats, and the associated anxiety.

In addition to the amount consumed, individual factors play a decisive role in the occurrence of an overdose. Low tolerance, such as that found in occasional users or after prolonged periods of abstinence, significantly increases sensitivity. Furthermore, polydrug use with other substances, particularly alcohol, enhances the effects unpredictably. Alcohol can accelerate the absorption of THC into the blood and potentiate the depressant effects on the central nervous system. The psychological state, the so-called set, as well as an environment with sensory overload also influence whether physical reactions escalate into a spiral of panic.

• Overstimulation of CB1 receptors in the central nervous system.
• Acute drop in blood pressure with a compensatory increase in heart rate.
• Increased susceptibility with low tolerance or after breaks in consumption.
• Unpredictable enhancement of effects due to simultaneous alcohol consumption.
• Influence of psychological state and a stressful environment on the course of the reaction.

Swiss context: Law, prevention, and emergency practice

In Switzerland, the legal situation regarding medical emergencies caused by substance use is clearly regulated. Medical assistance always takes priority, which is why emergency services and medical personnel are bound by professional confidentiality and do not report incidents to law enforcement authorities. Users therefore do not need to fear any legal consequences if they call the ambulance service on 144 due to a green-out. For telephone consultations in the event of symptoms of poisoning, the national emergency number 145 from Tox Info Suisse is also available 24/7, offering professional support free of charge and anonymously.

Nevertheless, the consumption of THC-containing cannabis above the legal limit of one percent total THC has legal consequences in everyday life. In road traffic, a strict zero-tolerance policy applies with a limit of 1.5 micrograms of THC per litre of blood, which can still be exceeded long after a green-out has subsided. Anyone caught driving while unfit to drive must expect their driving licence to be revoked. Possession of more than ten grams of cannabis can also lead to fixed penalty fines, which is why prevention projects and state-monitored pilot trials are increasingly focusing on education.

• Medical confidentiality protects consumers from prosecution during emergency calls.
• Free and anonymous advice in the event of an overdose via Tox Info Suisse on 145.
• Strict zero-tolerance in road traffic with a limit of 1.5 micrograms of THC per litre of blood.
• Legal limit of less than one percent total THC for legal products.
• Education on overdoses as an integral part of the Swiss pilot trials.

Differential diagnosis and differentiation from other crises

For first aiders and those affected, it is important to distinguish a common green-out from far more dangerous conditions. While the symptoms of a THC overdose usually subside on their own within a few hours, contaminated products or synthetic cannabinoids can trigger life-threatening crises. Synthetic substances, which are often added to illicit flowers, frequently cause extreme seizures, severe hallucinations, or life-threatening cardiac arrhythmias that do not occur in this form with natural cannabis. If consumption of such synthetic substances is suspected, medical assistance must be requested immediately.

In addition, a cannabis-induced panic attack must be distinguished from purely physical circulatory weakness. A panic attack manifests primarily through hyperventilation, fear of death, and a feeling of loss of control, while the circulatory system may remain stable. Reassuring words, breathing exercises, and shielding from stimuli help here. If, on the other hand, there is an actual circulatory collapse with imminent loss of consciousness, physical positioning is crucial. The shock position with elevated legs stabilizes blood flow to the brain, but must not be used in the event of vomiting due to the risk of aspiration.

• Differentiation from synthetic cannabinoids, which can trigger severe seizures.
• Distinction between a psychological panic attack and physical circulatory collapse.
• Shock position for circulatory stabilization only when fully conscious and not vomiting.
• Importance of breath regulation to prevent hyperventilation.
• Necessity of professional medical evaluation for persistent chest pain.

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