What causes schizophrenia?
The cause of the illness is more or less unknown. Today, however, some factors are known to increase the risk of developing schizophrenia – research has revealed that heritage and environment can determine whether an individual develops schizophrenia or not. Heredity is closely related to the illness as the risk of developing schizophrenia is about 10% if one of the parents has it, compared to 1% in the general public. If both parents or a person’s identical twin suffers from the illness, the risk is 40-50%. Unfortunately, it is not merely a single gene that determines whether a person develops schizophrenia or not, but rather several different genes which each contribute to increasing the risk of developing schizophrenia. These genes are called ‘susceptibility genes’ because they also increase the risk of developing other mental illnesses such as manic-depressive illnesses.
As mentioned, it is not only the genetics that determine whether an individual develops schizophrenia. One identical twin can develop schizophrenia without the other twin developing it as well, even though their genetic material is identical. Here, the environment decides whether a person’s genes are expressed. Currently, not all genes or environmental factors, which are related to the development of the disease, are known. Among the known environmental factors, however, are complications during pregnancy and childbirth, infections during pregnancy, the parents’ age, whether the person has smoked cannabis before turning 15, and if the person lives in the city or countryside.
Excess of methionine leads to disturbances in foetal brain development
A recent study, published in august 2017, has highlighted a new factor which possibly plays an important role in the risk of developing schizophrenia. They found that an increased concentration of a certain amino acid in pregnant mice is associated with a greater risk of the offspring developing schizophrenia. Researchers hope that this discovery can contribute to the development of more effective treatments and better preventive measures.
The amino acid, which the researchers investigated, is called ‘methionine’. It is an essential amino acid that the body is unable to produce on its own and thus needs added via the diet. It is necessary for the methylation of DNA; a process that is decisive of how the genes are expressed. As schizophrenia is an illness caused by developmental disturbances, genetic errors and epigenetic changes, and as the process of methylation is involved in all three processes, it seems very likely that an increased level of methionine can affect the risk of developing schizophrenia.
Methionine can be found in cheese and other dairy products, eggs, beans, several types of seeds and nuts as well as certain kinds of meat. The study revealed that an abundance of methionine in the blood of a pregnant mouse can lead to a faulty development in the brain of the foetus, and this can then lead to schizophrenia later in life. The study is based on studies of mice that were given three times the normal dose of methionine in the third week of pregnancy. The brain of the foetus begins to develop during the third week. The experiment showed that the offspring, which was exposed to a high concentration of methionine, expressed developmental disturbances corresponding to schizophrenia. This conclusion was based on results from nine different tests of the mice, which examined several different symptoms and changes that are connected to schizophrenia.
Afterwards, the researchers attempted to treat the mice with the same medicine often used for patients with the illness. This type of medicine is referred to as ‘antipsychotic drugs’. The treatment proved to be effective in the mice with schizophrenia. The scientists now want to conduct research in the field of behavioural disturbances on the molecular level to find new methods for treating schizophrenia. Perhaps, they can invent a treatment that reverses the changes caused on the brain tissue because of excess levels of methionine, or ways of regulating the metabolism of methionine. Hopefully, their results will be successful and create a new treatment which can prevent the development of schizophrenia.
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