Schizophrenia is a very serious mental illness where individuals are unable to differentiate between reality and imagination. It is the most common type of psychotic illness and is thought to affect up to 1 in 100 people in the UK during their lifetime.
Schizophrenia results in a disturbance of thoughts and feelings and can lead to odd and troubling behaviours. It is often mistaken for, and incorrectly labelled as, ‘split personality’, which makes the perception of it inaccurate and therefore more difficult to understand.
It is usually diagnosed between 15 and 35 years of age and men and women are equally affected.
Of the people who are diagnosed with schizophrenia, 1 in 4 will make a full recovery within five years of their first episode of the condition, with 2 out of 3 individuals making a recovery only to have another episode at some point in their lifetime. Sadly, up to 1 in 5 people will continue to have problematic episodes of schizophrenia throughout their lifetime, which can have a negative impact on their quality of life.
The Diagnostic and Statistical Manual of Mental Disorders (DSM) defines schizophrenia as being: “characterized by delusions, hallucinations, disorganized speech and behaviour, and other symptoms that cause social or occupational dysfunction.”
A slightly more accessible definition comes from the Cambridge English Dictionary, which defines it as: “a serious mental illness in which someone cannot understand what is real and what is imaginary.”
What are the causes of schizophrenia?
Like many mental illnesses, trying to identify a single cause for schizophrenia is very difficult and it is likely that the condition is caused by a combination of factors that will be unique to the individual.
Possible causes may be due to:
- Brain chemistry and structure.
- Major life events and traumas.
- Substance abuse
- Pregnancy and birth complications.
Schizophrenia is thought to run in families but with no single gene being responsible; instead it has been argued that a combination of genes may be a risk factor for inheriting the condition. An individual is ten times more likely to be affected by schizophrenia if they have a parent who also has the condition.
Other research has shown that if one identical twin (where DNA is identical) has it then the chances of the other twin also experiencing it are 1 in 2. This reduces to a 1 in 7 chance for twins who are non-identical (also known as fraternal).
Therefore, there does seem to be some link to genetics, but the fact that not all identical twins develop schizophrenia if one of them has it, leads researchers to believe that there must be other factors that go alongside genetics as a potential cause.
Brain chemistry and structure
The neurotransmitter ‘dopamine’ has long been thought to have some part in the development of schizophrenia.
It is argued that an individual who has too much dopamine in one area of their brain whilst lacking it in another, will develop symptoms of the condition. This theory is backed up by the fact that some illegal drugs will cause an increase in levels of dopamine, and when this happens symptoms of schizophrenia will become apparent in an individual who does not have a diagnosis of the condition.
The structure of the brain has also been thought to be linked to schizophrenia, although it is not known whether schizophrenia causes a difference in brain structure or differences in brain structure cause schizophrenia. Many people with the condition have been found to have enlarged brain ventricles, which are thought to be the result of poor brain development. Also, it has been noted that people with schizophrenia have a smaller hippocampus and poor neural connections, all of which are thought to play some part in the development of schizophrenia.
Major life events and traumas
Although a major life event is unlikely to be a single cause of schizophrenia, it may act as a trigger for someone who is already susceptible to it because of another factor.
A major stressful event such as the death of a loved one or becoming unemployed causes big changes in someone’s hormone levels as they try and recover from the shock. It is not known exactly how, but these changes are thought to be involved in the development of schizophrenia.
Poor family relationships are thought to be an event that is involved in schizophrenia particularly for children who are repeatedly exposed to contradictory messages from their parents. For example, Bateson et al. (1956) found that children may not respond appropriately to certain instructions and interactions because they do not know which of the contradictory messages to act upon. This, it is argued, can lead to the child not knowing what is real and what is not – something which is a major symptom of schizophrenia.
Like other potential causes of schizophrenia, substance abuse is not thought to be a direct cause but can increase the risk of its development.
Some drugs make individuals even more susceptible, such as cocaine and amphetamines, because these two drugs can lead to psychosis, which may trigger the onset of schizophrenia.
Three major studies have found that individuals under the age of 15 who use cannabis regularly are up to four times more likely to develop schizophrenia by the time they reach the age of 26.
If an individual already has a diagnosis of schizophrenia, then substance abuse can make the symptoms worse. Additionally, if the individual is taking prescribed medication to treat the symptoms of their condition, then alcohol and some illegal drugs can reduce the effectiveness of the medication.
Pregnancy and birth complications
It has been found that some individuals who experience schizophrenia may have been subject to a traumatic or complicated birth.
Factors such as a lack of oxygen at birth (known as asphyxia), low birth weight or being premature may affect brain development, which can be a risk factor in the development of the condition.