Does cannabis make you schizophrenic?

The question of whether cannabis makes you schizophrenic is understandable, but it is put too crudely. According to addiction prevention, cannabis can increase the risk of psychotic symptoms. Whether this leads to schizophrenia depends on several factors, and according to the current state of research there is no simple chain of cause and effect. This article explains the terms, the state of the studies and the practical consequences.

What the terms mean

A psychosis is a severe mental disorder in which perception and thinking are markedly changed. Schizophrenia belongs to this area and is a separate illness. Both terms are often mixed up in everyday life. Anyone who talks about the risk should therefore speak of psychoses and not generally of schizophrenia.

The distinction matters because studies mostly examine psychotic symptoms. A finding about psychoses cannot automatically be transferred to a diagnosis of schizophrenia.

What prevention says about the risk of psychosis

Addiction prevention emphasises that the harmfulness of cannabis depends on the age of the person using it and on how often they use it. Young people are particularly at risk. In addition, individual predisposition plays a role. With an inborn predisposition to psychosis, even small amounts of cannabis could be enough.

Prevention also points out that the link is statistical. This means that people who use cannabis are seen to develop psychosis more often. It does not mean that cannabis is in every case the cause.

The role of predisposition

Drugcom describes a vulnerability-stress model: some people bring a genetically based susceptibility to schizophrenia, and external strains can trigger a psychosis in people with such a susceptibility. In this sense, cannabis counts as a possible stress factor for the brain. According to drugcom, this is not yet proven beyond doubt. Still, the indications are growing.

Anyone who knows of psychoses in the family should therefore speak to a doctor. What matters is the interplay of predisposition, environment, age and pattern of use.

The THC content

A study summarised by drugcom reports roughly double the risk of psychotic symptoms with cannabis that has a high THC content. The THC content is therefore a factor in its own right.

Drugcom also describes that the risk of psychosis rises with the intensity of use and seems to be particularly high with varieties that have a high THC content. A single study cannot settle an individual case. It does show where caution makes sense.

Age and years of use

An analysis by drugcom describes a markedly increased risk for young people. According to this study, the risk for 12 to 19-year-olds who use cannabis is roughly 11 times higher than for peers who do not. Such figures come from individual studies and should not be read as fixed quantities. They do show, however, why young people should be especially protected.

The young brain is in an important stage of development. THC can disrupt maturation processes in the brain. Anyone who starts early therefore takes on a greater risk.

Why a statistical link does not prove a cause

A study can show that two things occur together. It cannot always prove that one causes the other. People who use cannabis differ in many respects from others. These include environment, stress, sleep and pre-existing conditions.

Prevention puts it plainly: the statistical link does not prove that cannabis actually causes a psychosis. Even so, the risk should be taken seriously, because it shows up in many studies.

Recognising warning signs

When perception or thinking change noticeably in a person, that is a reason to seek medical help. This applies especially when changes persist for days or weeks or get worse. Do not wait until the situation becomes unclear.

A GP can take the first step and refer on to the right service. In an emergency, call the emergency number 112.

What parents and relatives can do

Parents and relatives are often the first to notice changes. A calm conversation helps more than reproaches. Ask concretely what the person is experiencing, and show that you are worried without judging.

Counselling is available for parents. The Elterntelefon (parents’ helpline) of the Nummer gegen Kummer can be reached on 0800 111 0 550. A local counselling service can also help with the assessment.

Prevention: where caution makes sense

Caution is particularly called for where predisposition, age or a high THC content come together. Anyone who knows of psychoses in the family should view their own use especially critically. For people under 18, possession of cannabis is not permitted under section 3 of the Cannabis Act (KCanG).

Under § 5 para. 1 KCanG, consumption in the immediate presence of persons under 18 is prohibited. Passing on cannabis is punishable under § 34 para. 1 no. 7 KCanG. Anyone over 21 who passes cannabis to a child or young person generally commits a particularly serious case under § 34 para. 3 KCanG.

Points of contact

For questions about your own use, you can reach the Sucht und Drogen Hotline on 01806 313031. For changes in experience or thinking, the GP is the first point of contact. In an emergency, the emergency number 112 is responsible.

What you can take from the findings

The most important point is this: with regard to the risk of psychosis, cannabis is far from harmless. At the same time, a psychosis is not an inevitable consequence. Anyone who knows their risk factors can adjust their use and way of life accordingly. Anyone who sees warning signs in themselves or others acts early and gets help.

Further reading: Which pre-existing conditions increase the risk of psychosis?, Which warning signs point to a psychosis? and Where can parents get counselling about cannabis? More topics are under Prevention and youth protection.

What you can do now

• If psychoses occur in your family, speak to a doctor about your risk.
• If you are under 18, get help from a counselling service with questions about use.
• For striking changes in yourself or others, seek medical help.
• If you are worried about your own use: addiction counselling or the Sucht und Drogen Hotline.