There have been many things that have been suggested as possible causes of mental illness. Different explanations can generally be divided into three categories: Biological factors Social and environmental factors Psychological make up of the individual All of these factors are important and interact with each other.
1 – Biological Factors
Physical things such as brain tumours or taking street drugs Genetics Brain chemistry Brain structure Physical development
Evidence for a genetic element in mental illness comes from research with twins and both biological and adoptive relatives of people with schizophrenia or bi-polar disorder. Research has found that the closer the biological relationship, the greater the risk of a relative also having the diagnosis.
The estimated probability of being given a diagnosis of schizophrenia is as follows: 46% for a child with both parents diagnosed 13% for a child with one parent diagnosed 9% for siblings. This is compared to the overall probability of 1% for the general population. Similar findings have been reported for bipolar disorder.
However, there has been some doubts raised about the methods used in these studies and it is very difficult to differentiate genetic inheritance from environmental factors. Most studies report that there is evidence for a combination of genetic and environmental factors.
Schizophrenia could result from an overproduction of dopamine. Dopamine is a neurotransmitter or brain chemical. Some anti-psychotic drugs that effect dopamine can induce parkinsonian type symptoms, such as shaking. Parkinsonism is known to be related to low dopamine levels so it is thought that the drugs work by lowering dopamine levels.
Drugs such as amphetamines increase dopamine production and can cause psychotic like experiences. However, we can not draw any conclusions from either of these two observations. The anti-psychotic drugs described have an immediate effect on dopamine in the brain but symptoms only improve gradually.
New drugs such as clozapine effect a different neurotransmitter (brain chemical), serotonin. Research is currently taking place to investigate this. The other major problem here is cause and effect. It is not known if the chemical changes cause the psychotic experience or if the experience causes the chemical change in the brain.
The only well established structural abnormality in the brain that has been found in people with psychosis is enlarged lateral ventricles (fluid filled spaces within the brain). Research suggests that different types of psychotic experiences are associated with different patterns in brain activity. Low levels of activity in the frontal lobes in the brain have been observed in people experiencing so-called ‘negative symptoms’.
However, the medication that people have taken over the years is not always taken into account.
It is also possible that psychological trauma or psychotic experiences themselves cause the changes in brain activity, rather than the other way around.
Brain scans of London taxi drivers have found that they have enlargements of certain brain structures, thought to be due to the amount of information they have had to store. This would suggest that it may be experience that causes the changes in brain structures rather than the changes in brain structure causing the experience.
Alternatively, one could also suggest that those who are successful at becoming London taxi drivers already have different brain structures!
People with schizophrenia are more likely to have: been born in the early months of the year experienced difficulties during birth been exposed to viruses in the womb These are all environmental theories that have been put forward but evidence is limited and many of these theories are speculative.
The evidence for specific biological mechanisms underlying mental illness is inconclusive. Some individuals may be more sensitive to environmental stressors than others and this will be reflected in some way in their brain chemistry. However, the evidence would suggest that there are also other factors involved in the underlying cause of mental illness.
2 – Social and Environmental Factors
Stress-Vulnerability Model Cultural Factors
Life Events Family Relationships
No one single cause for mental illness has been found and it is likely that many aspects of an individual’s life are significant in producing psychotic experiences. This has been described as the ‘stressvulnerability’ model. As discussed earlier, everybody has a different level of sensitivity to environmental stressors. This sensitivity is known as vulnerability. A person’s level of vulnerability could be caused by biological factors, discussed earlier, or be a result of events that have happened previously in a person’s life
The stress-vulnerability model suggests that problems will only occur when environmental stressors are present. The amount of environmental stress required to cause problems will differ according to the vulnerability of the individual. This model would explain why some people develop psychological problems when others don’t even if the have gone through the same stressful events.
Although psychotic experiences tend to be similar across different cultures, people in different cultures describe psychological problems in very different ways. Some cultures may describe psychological problems in physical terms (such as pain), whereas other cultures will describe the same problems in emotional terms (anxiety).
Sometimes explanations can be misinterpreted if the context in not understood. For example, in some cultures, many people believe in the possibility of being possessed by demons, but in other cultures this could be wrongly thought of as a ‘delusional’ belief. It has also been found that the experiences of people from different cultures may be responded to differently by medical professionals. For example, research has shown that black people are more likely to receive a diagnosis of schizophrenia than white people, even if their experiences are the same.
It has been suggested that social exclusion (e.g. racism) can increase the likelihood of developing a mental illness. However, such findings require further investigation.
Many people who have psychotic experiences have experienced abuse or trauma at some point in their lives. They are also likely to have experienced a greater number of stressful events in the 6 months before an episode. It appears that stress is associated with the onset of psychotic symptoms in vulnerable individuals. Also, once someone has experienced a psychotic episode, high levels of stress make it more likely that the problems will return.
Difficult family relationships in childhood and adolescence may be an important contributing factor for some people. Research has also found that family can play an important role in the recovery of a person diagnosed with a mental illness. Friends and family of someone who is having psychotic experiences can find it difficult to cope with certain behaviours and can become critical or hostile toward the individual. Equally some families can find the changes very upsetting and will treat the individual like they are a child again. These reactions have been described as ‘high expressed emotion’ and have been found to lead to poorer outcome during recovery and an increased likelihood of relapse.
Psychologists usually assume that people who report psychotic experience are either having unusual perceptual experiences (hearing voices) or they are interpreting normal experiences in an unusual way. Psychologists then look for reasons as to why this may happen.
There could be problems with the structure or functioning of the brain that can lead to impairments in processes such as perception, memory and attention (attention deficits). Other people may misinterpret normal life events. For example a traumatic event during childhood could effect the way which you interpret future events (cognitive biases). All events will be interpreted from the perspective that the person has developed. People therefore differ in the way they respond to different stresses and also the way they understand and make sense of psychotic experiences.
There is evidence to suggest that some people with schizophrenia have difficulties on a variety of measures of attention. Some people who are having a psychotic experience lose the ability to interpret other people’s actions and speech in order to understand what they might be thinking. Cognitive deficits have been suggested as possible causes of disorganised speech, hearing voices and unusual beliefs.
Deficits in information processing can leave people more vulnerable to psychotic experiences. When people with these vulnerabilities experience stressful events, the deficits make it harder for them to cope. Emotional stress can lead to an increase in cognitive deficits, which in turn can lead to further problems and the development of a vicious circle.
Many studies have found that people with unusual or delusional beliefs tend to ‘jump to conclusions’ when they have limited information. Research also suggests that unusual beliefs are associated with specific biases in reasoning about social situations. For example, people who experience paranoia have a general tendency to assume that other people cause the things that go wrong in their lives.
There is also evidence that some people who experience auditory hallucinations have difficulty distinguishing their inner speech (thoughts) from speech from an external source. This has been shown in brain scans, where areas of the brain associated with speech are active when people hear voices. Also, in other experiments, people who hear voices have been shown to have difficulty when they are asked to distinguish between their thoughts and words spoken to them.
It is possible to understand many psychotic experiences as a result of how the person sees the world, or particular problems with thought processes or both. For example, if you are experiencing emotional stress, you might find it hard to interpret other people’s actions and intentions. This could make interactions anxiety provoking. If events in your life have led you to believe that people hurt you at every opportunity, and you have a tendency to jump to conclusions, it is understandable that you might feel paranoid.
All of the factors that have been discussed are important and can interact with each other. Although there is some evidence that genetics and brain chemistry and structure are involved in developing psychosis, the evidence is not conclusive. The evidence suggests that some people are more vulnerable to environmental stressors than others, but biological factors alone cannot explain the underlying causes of mental illness. The stress-vulnerability model suggests that problems will only occur when environmental stressors are present. The amount of environmental stress required to cause problems will differ according to the
To summarise, there is no single explanation for the underlying causes of mental illness. Research over the last few decades has shown that psychotic experiences are influenced by social and psychological factors as well as biological ones. When psychological, social and biological factors interact, especially when stressors occur, psychotic experiences can be the result.