What role does THC content play in risk?

A higher THC content is linked, according to a study summarised by drugcom, to roughly twice the risk of psychotic symptoms. However, the content does not describe the risk on its own, because frequency of use, age and personal predisposition also matter. In law, THC content matters in two places: when cannabis is supplied to young adults and in road traffic.

This article explains what the value means, which risks specialist agencies link to it and which limits the law sets. Product comparisons are outside its scope.

What THC content measures

THC stands for tetrahydrocannabinol and is the active substance in cannabis that mainly determines its intoxicating effect. The content is given as a percentage. A higher figure means the same amount of plant material contains more active substance. This is a difference you cannot see when you use cannabis.

What specialist agencies say about the risk

• A study summarised by drugcom reports that high-strength cannabis roughly doubles the risk of psychotic symptoms.
• The drugcom drug encyclopedia writes that the risk of psychosis rises with the intensity of use and seems to be particularly high for people who mainly use high-strength varieties.
• Cannabispraevention.de describes for young people: the higher the THC content, the more dangerous. THC disrupts the brain's maturation processes.
• According to the BIÖG, roughly one in eight people who use cannabis become dependent. The risk rises if you use one or more times a week.

A single study does not decide an individual case. It does, however, show that strength is a risk factor in its own right. The statistical link does not, according to cannabispraevention.de, prove that cannabis actually causes psychosis. More on this is in the article How solid is the research on psychosis risk? and in the article Can cannabis cause schizophrenia?

The limit for young adults in the law

The KCanG sets different rules by age for supply by cannabis associations (Anbauvereinigungen). Stricter limits apply to young adults, that is, people aged between 18 and 21. Cannabis associations may supply them no more than 25 grams of cannabis per day and no more than 30 grams per calendar month, and the THC content may not exceed 10 percent (section 19(3) KCanG). For members aged 21 and over, the limits are no more than 25 grams per day and 50 grams per calendar month.

These rules apply only to supply by cannabis associations. They are maximum limits and say nothing about what is advisable. For a closer look at where the boundaries lie, read What does the law say for 18- to 20-year-olds?

The limit in road traffic

Drivers face a different standard. Under section 24a(1a) StVG, anyone who drives a motor vehicle in road traffic commits an administrative offence if they have 3.5 ng/ml or more of tetrahydrocannabinol in the blood serum. This value refers to the concentration in the blood and has nothing to do with the content of a product. Anyone who also consumes an alcoholic drink, or makes the journey under the influence of an alcoholic drink, commits an administrative offence under section 24a(2a) StVG, and the fine range is higher.

Strength, quantity and form of use

Strength describes only part of what happens when you use cannabis. The form of use also matters: cannabispraevention.de describes that with edibles, meaning cannabis in biscuits or drinks, the effect is delayed, often arrives suddenly and, depending on the dose, lasts about five hours. This form of use is regarded there as particularly risky. If you do not know the quantity and strength, you can hardly predict your own reaction.

Why figures alone are not enough

A percentage sounds precise but says nothing about the individual person. Two products with the same content can feel different depending on quantity and form of use. A number therefore does not replace caution.

• If you do not know the strength, you cannot estimate your own risk.
• Cannabis and alcohol together strain the circulation heavily and often lead to nausea and vomiting, according to cannabispraevention.de.
• Before driving, avoid cannabis entirely.

Practical questions before use

If you are unsure, you can ask yourself a few questions. They help you make your own decision soberly.

• Do I know the strength of the product, or am I guessing?
• Do I plan to drive afterwards or take on responsibility?
• Have I already taken other substances today, including alcohol or medication?

If any of these questions remains unclear, it is a good moment to avoid cannabis. A counselling service can help you practise such decisions in everyday life.

What to keep in mind about numbers

A figure such as 3.5 nanograms of THC per millilitre of blood serum is a legal threshold and says nothing about the effect in an individual case. Anyone who hears figures on products, in the law or in conversation should ask what exactly they measure.

Where to get help

If you are unsure how to deal with strength and quantity, a counselling service can help. The Suchthilfeverzeichnis of the Deutsche Hauptstelle für Suchtfragen lists counselling services in your region. The Sucht & Drogen Hotline of the BIÖG can be reached on 01806 313031. A doctor can also assess the situation. For mixed use, read the article What happens when cannabis and alcohol are used together?