What happens when cannabis and alcohol are used together?

Together, cannabis and alcohol place a heavy load on the circulatory system, according to the BIÖG, and often lead to nausea and vomiting. Feel-ok writes that both substances have negative effects on concentration and reaction ability, and that their effects can reinforce one another. In road traffic, the combination is covered as a separate offence in section 24a para. 2a of the Road Traffic Act (StVG).

This article explains what the combination means for the body and everyday life, which rules apply in road traffic and how you can reduce the risk. It does not replace medical advice. It does, however, show where the limits lie.

Why the combination is hard to assess

Feel-ok names a particular effect of alcohol: it leads people to overestimate themselves. That makes it harder to recognise your own impairment. According to feel-ok, the effects of different drugs can reinforce one another. The Deutsche Hauptstelle für Suchtfragen (DHS) lists cannabis combined with nicotine, ecstasy, amphetamines, cocaine, crystal meth and hallucinogens among dangerous mixtures.

According to the Bundesgesundheitsministerium (Federal Ministry of Health), the reaction to cannabis depends, among other things, on state of health, mixed use and the amount taken. There is therefore no reliable rule of thumb for the combination.

The rules in road traffic

For cannabis, the limit in road traffic is 3.5 nanograms of THC per millilitre of blood serum. For alcohol, the limit is 0.5 per mille in the blood. Both limits are set out in section 24a of the Road Traffic Act (StVG). Anyone who reaches one of the two limits while driving a motor vehicle commits an administrative offence. The fine range follows from section 24a para. 3 StVG, and as a rule a driving ban is also to be imposed (section 25 para. 1 StVG).

The combination is a separate case. Under section 24a para. 2a StVG, anyone who commits an act under para. 1a (that is, drives a motor vehicle with 3.5 ng/ml THC or more in blood serum) and at the same time consumes an alcoholic drink, or sets off while under the influence of an alcoholic drink, commits an administrative offence. The fine range is higher than under para. 1a (section 24a para. 3 StVG). Novice drivers in their probationary period and drivers under 21 are subject to a separate ban on cannabis and alcohol (section 24c StVG). The exception applies only if the THC value comes from taking a medicine prescribed by a doctor, as intended (section 24a para. 4 StVG).

What happens in the body

The BIÖG names the strong load on the circulation as well as nausea and vomiting. The DHS lists, among the acute effects of cannabis, reduced reaction and memory, dizziness, a pounding heart and disorientation. Anyone who notices serious discomfort or confusion after consuming both should seek help without delay.

Drugcom describes how psychological dependence can develop with long-term cannabis use.

How you can reduce the risk

The safest measure is to avoid the combination altogether. Anyone who consumes anyway can keep these rules in mind:

• Do not consume both at the same time, and leave clear time between the substances.
• Plan a route for the evening that does not need a car, such as a taxi or a lift with someone who does not consume.
• Drugcom points out that driving ability can still be impaired even after the acute intoxication has worn off. Therefore allow time before you drive.
• Pay attention to amount and frequency, and take breaks.

If you consume together with others, agree in advance who will not drive.

Why young people should take particular care

The BIÖG points out that the young brain is in an important stage of development, and that use can affect this development. The BIÖG says young people are far more at risk from cannabis than adults. A detailed explanation of the age limits is in the article From what age may you possess cannabis?.

What friends and relatives can do

If a friend has consumed both and wants to drive afterwards, speak to them directly and offer another way home. If the situation is acute, call the emergency number 112 if in doubt.

If you are affected yourself, you can contact an addiction counselling service. There you can discuss how to avoid combinations.

What to do after an incident

If someone has complaints after consuming together, seems confused or loses consciousness, every minute counts. Do not leave the person alone, place them in the stable side position and call the emergency number 112. Tell the emergency services which substances were consumed, so that the team can assess the situation correctly.

Legal consequences of driving under the influence are explained by a lawyer who specialises in traffic law.

Where to get help

If you notice that you regularly consume both or can no longer stop, speak to an addiction counselling service or a doctor. Anonymous advice is available from the Sucht & Drogen Hotline on 01806 313031 (calls are charged, daily 8 a.m. to midnight). The Deutsche Hauptstelle für Suchtfragen maintains an addiction support directory, which lists counselling services near you. For acute complaints after consumption, call the emergency number 112. More on warning signs in everyday life is in the article What are the health effects of cannabis overall?.