Which pre-existing conditions increase the risk of psychosis?

As a predisposition, the sources name above all an inborn tendency. Gesundheitsinformation.de describes a higher risk when a parent or sibling has schizophrenia (about 12 per cent of children of mothers or fathers with schizophrenia later also develop it). According to this source, sleep disorders, psychological stress and traumatic experiences are added. For cannabis, the BIÖG and drugcom additionally name starting use at a young age, frequent use and a high THC content. The DHS writes that existing mental illnesses can worsen with heavy use. Which pre-existing conditions play a role for you can only be assessed by a doctor.

What psychosis is and where cannabis comes into play

Psychosis is a severe mental disorder. Perception, thinking and feeling can change so strongly that contact with reality is lost. The Bundesinstitut für Öffentliche Gesundheit (BIÖG) describes the link with cannabis as follows: people who use cannabis develop psychosis more often than people who do not.

There is no automatic outcome from this. The link is described statistically, and causation in an individual case is not proven. According to the BIÖG, it is equally possible that people with a tendency towards psychosis turn to cannabis more often.

Which risk factors do the sources name?

• An inborn predisposition. According to the BIÖG, with such a predisposition even small amounts could be enough to trigger a psychosis.
• Starting at a young age. The harmfulness of cannabis depends on the age of the person using it, and according to the BIÖG important maturation processes take place in the brain until around 25.
• Frequent use. The frequency of use also determines how harmful cannabis is.
• A high THC content. A study reported by drugcom sees roughly double the risk of psychotic symptoms with cannabis that has a high THC content.

For young people, drugcom names a further figure: among 12 to 19-year-olds, an 11-fold higher risk of a psychotic disorder is cited in connection with use. This figure comes from a single analysis. It says nothing about how it looks for you personally, but it shows why protecting young people takes priority.

What the figures mean and what they do not

“Twice as high” and “11-fold” describe a ratio between two groups. They do not say how common a psychosis is overall. For comparison, Gesundheitsinformation.de estimates that schizophrenia is diagnosed in about 0.5 per cent of people over the course of their life. The sources read do not give a figure for how many users become ill.

Classifying pre-existing conditions and predisposition

According to the sources, a psychosis or schizophrenia in the immediate family, as well as existing mental illnesses, count as a predisposition. Whether and how strongly this applies to you is a personal medical question.

The BIÖG writes that whether one belongs to the people with an inborn predisposition cannot readily be said. An honest question helps: were there psychoses or severe mental illnesses in your family? If you are unsure, speak to a specialist.

The risk factors at a glance

Factor	What the sources say	Source
Inborn predisposition	Even small amounts can be enough	cannabispraevention.de
Age at the start	Harmfulness depends on age; young people are particularly at risk	cannabispraevention.de
Frequency of use	Frequency also determines the harmfulness	cannabispraevention.de
High THC content	Roughly double the risk of psychotic symptoms in one study	drugcom.de

What this means for your decision

The BIÖG writes that, as a rule, several risk factors are usually involved in the development of a mental disorder. Anyone who carries several of the named factors at once, for example family predisposition, an early start and frequent use, has a reason to review their own use seriously. This does not amount to a diagnosis.

The BIÖG writes that young people should not use cannabis at all, for health reasons. For adults with a predisposition, a conversation with a doctor is the sensible first step.

Recognising warning signs and getting help

The article on warning signs of psychosis explains which signs may point to a psychosis. The principle here is this: if you or someone in your circle experiences perception, thinking or feelings as strongly changed, a medical examination is the right step. Do not wait for it to pass on its own.

The view of the family

A psychosis in the family can be a sign of a predisposition. You can pass this information on factually in a conversation with a doctor; the essentials are enough.

When use becomes a topic

There is reason to review use when mood, thinking or perception have seemed different for a longer time than before. This also applies when friends, a partner or family members report such changes to you. Taking such feedback seriously is often the most important first step.

What you can do now

• Speak to a doctor if there are psychoses or severe mental crises in your family.
• Check your use honestly, for example with the self-test guide.
• Take changes in mood, thinking or perception seriously and have them checked by a doctor.
• Note: the higher the THC content, the more dangerous, writes the BIÖG.

For a confidential conversation, you can reach the Sucht & Drogen Hotline on 01806 313031 (calls are charged, daily 8 a.m. to midnight). More on prevention is available under Prevention and youth protection. Counselling does not replace medical treatment.