At this stage, research has yet to completely explain the cause of psychosis. However, it is clear that the causes are complex. The most widely accepted theory is the stress-vulnerability model which suggests that a combination of biological/genetic factors and environmental factors increase someone’s “vulnerability” to experiencing symptoms of psychosis. This suggests that someone can have a genetic vulnerability to psychosis and never develop any symptoms!
A number of environmental and biological factors have been identified to increase the risk of psychotic symptoms. These include cannabis use, acute stress, trauma, childhood adversity, migration, obstetric complications, prenatal infection, maternal malnutrition and/or stress during pregnancy. It’s important to keep in mind that it’s no single factor that causes psychotic symptoms but a complex combination of factors.
A helpful way to understand this model is using the image of a bucket, where the size of the bucket represents vulnerability and water represents stress. Someone who is more vulnerable to psychosis (i.e. has more risk factors) will have a smaller bucket compared to someone who has less vulnerability. As stress occurs in life, water begins to fill the bucket. If the bucket overflows, psychotic experiences may occur. However, if someone is able to cope well with stress, it is as if there is a tap at the bottom of their bucket that relieves the pressure by releasing some water. If they don’t have the skills to cope with stress or cope with stress poorly, it’s as if this tap doesn’t work and their bucket overflows.
Therefore, while we are unable to change many of the factors that can occur that increase the likelihood that someone experiences psychosis (the size of the bucket), psychologists and Psychiatrists are able to provide assistance to reduce the level of stress someone is experiencing and/or help them to better cope with that stress.
Psychosis: A bit of brain science…
How does the combination of biology/genetics and stress cause psychosis? Research still has a long way to go on this front, however, a number of findings have brought some light to this question and seem to suggest dopamine, a neurochemical in the brain, plays an important role:
- Excessive amounts of dopamine have been found in individuals with a higher risk of psychosis, and this worsens as symptoms worsen.
- Environmental stress also causes dysfunction in dopamine.
- Some of the genes associated with psychosis are related to dopamine function and response to stress.
- Anti-psychotic medications affect the dopamine system.
- When healthy individuals take substances that increase dopamine, psychotic symptoms occur.
- High levels of dopamine cause people to see ordinary and everyday sensations and experiences as meaningful and significant. For example, security cameras that otherwise would be ignored could become ever-present (due to increased attention to them) and significant (could be interpreted as someone watching them or persecuting them).
This theory has been called the dopamine hypothesis. Researchers continue to explore the causes of psychosis to clarify and improve our understanding and to improve the treatments that are available.