What causes psychosis?

• What causes psychosis?
• Genes
• Dopamine
• Changes in the brain
• Birth complications
• City life, migration and social adversity
• Drugs
• Childhood adversity

What causes psychosis?

Researchers don’t believe there is one single cause of psychosis. Instead, they think there are different factors that contribute to the development of the symptoms. Some of the factors are genetic and some are ‘environmental’ – drug use, stressful life events or complications at birth, for example.

Many different research studies have discovered potentially contributing factors, but it is not yet known how all these different elements fit together, are linked, or interact to cause the symptoms of psychosis. Research studies continue to try to fit all the pieces together: these include brain imaging studies, projects studying DNA and genes, and studies tracking individuals with a diagnosis of psychosis and their families.

More than 200 families who have experience of schizophrenia or bipolar disorder, for example, have taken part in the Institute of Psychiatry-based Maudsley Family Psychosis Study for the past 15 years to help researchers find out more about genes and about environmental factors that influence the development of psychosis.

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Genes

Scientists have already identified a number of genes that seem to play a role in the development of psychosis.

Studies of twins and analysis of DNA are showing that the same genes seem to be involved in schizophrenia and bipolar disorder. Scientists think that there are probably a set of genes that make people more susceptible to developing psychosis.

People who inherit the genes do not necessarily develop psychosis. Other factors trigger its development. Other factors also determine whether the psychosis is expressed as a symptom of schizophrenia, or a symptom of bipolar disorder.

At the Institute of Psychiatry, genetic research is carried out in purpose-designed laboratories dedicated to specialist technologies and techniques. Researchers carry out these studies with the help of a bank of DNA samples donated by people with schizophrenia and bipolar disorder, and from healthy volunteers to allow comparisons to be made in the search for genetic variations. IoP researchers also contribute to large multinational studies searching for genes that have a role in psychosis.

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Dopamine

Dopamine is one of many chemicals in the brain that are used to pass information from one brain cell to another. It is a ‘neurotransmitter’.

Research has shown that the abnormal production of too much dopamine can lead to hallucinatory experiences, delusions and disordered thoughts.

People who may be at risk of developing schizophrenia also have increased levels of dopamine in their brain.

Scientists don’t yet know, however, why dopamine levels increase in some people. They believe dopamine is what they call the ‘final common pathway’ to psychosis – dopamine levels may rise for a number of different reasons (some of them are listed on this page) but it is the increase that prompts the symptoms of psychosis.

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Changes in the brain

Research over the past 25 years has shown that there are structural changes in several brain regions that may in turn lead to changes in the way the brain works and cause the symptoms of psychosis. These changes may affect processes in the brain like thinking, reasoning, understanding, attention, working memory and decision-making, and may be linked to abnormalities in the levels of dopamine.

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Birth complications

Researchers have shown that people who had complications when they are born – were premature, for example, or were starved of oxygen (hypoxia) – have an increased risk of developing schizophrenia. However, many babies who are born prematurely and have other complications at birth do not develop psychosis, and people who had normal births can also go on to develop the symptoms

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City life, migration and social adversity

Long-term studies in countries in the West have consistently shown that people who are born and live in cities have a greater risk of getting psychosis than people living in the country. Researchers are continuing to study why this is: one theory is that it’s easier to become isolated and paranoid in the city, and that drug use is more common.

Researchers think that people who migrate are more at risk, as are those who face adversity in life. Some researchers think severe and chronic social stress may impact on the dopamine system and cause it to produce high levels of the chemical.

At the moment, black people living in England stand a far greater chance of developing schizophrenia or bipolar disorder than white people. Research has shown that people of black African descent are six times more likely to develop both illnesses. People of African-Caribbean descent are nine times more likely to develop schizophrenia and eight times more likely to develop bipolar disorder than their white contemporaries.

But studies in Jamaica, Trinidad and Barbados have shown black people living there are no more likely to develop psychosis than white people living in England.

Researchers are analysing the differences and similarities in the lives of black and white people in England who become ill with psychosis. They think social exclusion may play a part in the development of psychosis: black people are more likely to be poor, more likely to be unemployed, more likely to be separated from their families and living alone. These factors, combined with the stresses of living in a big city, may be associated with a higher risk of developing the symptoms.

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Drugs

The use of street drugs, particularly cannabis, increases the risk of developing psychosis (see Cannabis page).

Research at the Institute of Psychiatry has shown that some people carry a certain type of gene that makes them more likely to develop the symptoms of psychosis if they smoke cannabis regularly during their teenage years, while their brains are still developing. The COMT gene is responsible for determining how fast dopamine is broken down in the brain.

Research has shown that regular use of other drugs, including amphetamines and cocaine, also increases the risk of developing psychosis. These drugs increase the levels of dopamine in the brain.

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Childhood adversity

Research has shown that a small proportion of people who develop psychosis have experienced abuse of some kind during their childhood. Studies have also shown that people with other mental health problems are more likely to have been maltreated physically, sexually or emotionally as a child.

However, not everyone who has psychosis or another mental health problem experienced abuse as a child, and not everyone who was abused during their childhood goes on to become mentally unwell. Researchers are therefore investigating how early abuse and the resulting trauma might play a part in the development of psychosis, and how that fits in with other factors that contribute to someone becoming unwell.

The first step is to try to understand more about the type of abuse people may have suffered in childhood. A study published in February 2010 by a team at the Institute of Psychiatry, for example, analysed information collected from people who had had a first episode of psychosis and found just over 12 per cent reported being physically abused by their mothers before their 12th birthday. Comparable information collected from people with no experience of psychosis showed just four per cent reported physical abuse from their mothers before secondary school age.

Department of Health policy says that staff working in mental health services should routinely ask people if they have experience of abuse. Staff should be trained to raise the issue, and to offer appropriate support and care if people choose to disclose past or current experiences to them. The policy was introduced to acknowledge and address links between violence, abuse and mental ill health.