|What causes psychosis?|
|What factors can predispose someone to experiencing a psychotic disorder?|
|What stressors can trigger a psychotic episode?|
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What factors can predispose someone to experiencing a psychotic disorder?Certain biological factors can predispose an individual to experiencing a psychotic disorder. Genetic factors, often revealed by having a close relative who has experienced a psychotic episode, can put a person at higher risk for developing a psychosis. If one parent has experienced a psychosis, then the chance of a child experiencing a psychosis is approximately ten to fourteen percent. However, many people who have experienced psychotic episodes have no family history of a psychotic disorder, and other people who have a family history of psychoses will never experience a psychosis. A family history of psychoses does not, by itself, mean that an individual will experience a psychosis.
Multiple genes involved in brain development have been associated with psychosis, and as our understanding of the functions of these genes develops, so will our understanding of this illness. We are in a very exciting time for expanding our knowledge of the intricacies of brain function as molecular and gene technologies develop.
Researchers also believe that certain differences in brain structure and function are strongly associated with psychoses. Using neuroimaging techniques, researchers have found that some individuals who have experienced a psychosis show an enlargement of the fluid-filled cavities in the brain (called the ventricles) and decreased size of some other brain regions. Interestingly, in identical twins discordant for psychosis (that is one twin is psychotic, the other is healthy), only the ill twin shows these significant differences. Nevertheless, the ‘healthy’ twin shows differences intermediate between the ‘normal’ population and their ill twin, again suggesting that they may have some fundamental susceptibility to developing psychosis. Decreased metabolic activity in certain other regions of the brain, and increases in other regions, has also been documented.
It should be noted that these studies have found only slight or subtle differences in brain structure and function between people who have experienced a psychosis and people who have not experienced a psychosis. Also, not all people who have experienced a psychosis show these differences and people who have never experienced a psychosis can also show these differences. Furthermore, it is not known if these differences are a cause or product of the illness. This means that these tests are, currently, of very little use in diagnosing a psychotic disorder. The problems may well exist at a chemical or molecular level which cannot yet be readily and accurately tested for in the brain. There are no definitive diagnostic tests for psychotic disorders, and therefore accurate diagnosis is left to an appropriately trained medical professional.
An association has been documented, in many studies, between psychotic disorders and complications during birth, or resulting from a viral infection or some other insult (e.g. exposure to toxic chemicals or starvation) during pregnancy. For example, in women who were infected with influenza during the 2nd trimester of pregnancy, there is a markedly elevated risk of psychosis in her offspring. This is an extremely critical period of brain development. It is believed that these factors, amongst others, can affect the structure and chemistry of the brain during early development, leading to long-lasting changes which increase a person's risk for developing a psychotic disorder later in life.
One brain chemical (neurotransmitter) that is believed to be intricately related to the expression of psychosis is dopamine. Researchers currently think that people who have experienced a psychosis may have too much of this brain chemical in certain brain regions, and too little in other regions. This role of dopamine in psychosis was first hypothesised through observations that agents which reduce psychotic symptoms (anti-psychotics) attenuate dopamine activity, while substances which increase dopamine activity (eg, amphetamines, cocaine), can precipitate psychotic-like symptoms. However, the fact remains that dopamine is only one of the neurotransmitters that have been implicated in psychoses. Unfortunately, the complexity of the brain and our relatively poor understanding of how it functions, even in people without psychosis, significantly hamper efforts at discovering new and better treatments for this illness. Nevertheless, we are in a time where treatments of psychotic illness have never been better.
There are many theories about the factors that might predispose someone to experience a psychosis, and understanding of these factors is improving all the time. However, much more research needs to be done in this area. Most of these theories centre on neurodevelopmental abnormalities. However, these theories are hard-pressed to describe psychotic illnesses which develop in later life.