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Schizophrenia and genetics: is it a hereditary disease?

Among the variety of pathologies in the field of mental health, one of the best known is schizophrenia. It is one of the most severe mental illnesses and affects 1% of the world’s population [1]. It is therefore important to know whether schizophrenia is genetic or acquired and, if so, what genetic factors may be associated with this disease. 

In most cases, schizophrenia occurs mainly in adolescence and early adulthood. It is not as common for this disease to emerge after the age of 45 years and, although residual, childhood schizophrenia also exists [3].

 

 

What is schizophrenia?

 

Schizophrenia is a severe brain disease characterized by an impairment of a person’s abilities, from emotional to perceptual to thinking [2]. People suffering from it may hear non-existent voices and think that other people want to harm them. On many occasions, the speech of affected persons is incoherent and noticeably affects working life and the ability to care for oneself.

Given the appearance of its first symptoms at a relatively young age, it was initially considered a dementia praecox, although it was later defined as a group of diseases [2]. Schizophrenia is associated with substantial morbidity and mortality and high personal and societal costs [4].

 

 

Symptoms of schizophrenia

 

The early symptoms of schizophrenia can be of three types:

  • Positive symptoms: they involve increased brain activity and are so called because they are additional behaviors that healthy people generally do not exhibit. Positive symptoms include hallucinations, delusions or disorganized thinking.
  • Negative symptoms: In contrast to positive symptoms, negative symptoms are related to a decrease in brain activity. Among these we find social isolation, problems in showing emotions, reduced communication, apathy, abulia (lack of energy or will) or absence of facial expressions.
  • Cognitive symptoms: The most characteristic would be problems with attention and concentration, memory and critical thinking.

Most commonly, patients present symptoms of schizophrenia of all types. The manifestation of symptoms usually appears between 16 and 30 years of age. Often, males develop these symptoms at an earlier age than females.

Although pharmacological treatments for schizophrenia exist, their efficacy is poor for most patients [4].

 

 

Is schizophrenia hereditary?

 

The exact causes of schizophrenia are not yet known, however, researchers indicate a combination of several causes: genetic, neurochemical and environmental. The genetic component plays a major role, so schizophrenia is considered a highly heritable disorder [4]. Current research is trying to locate a gene or group of genes that are associated with an increased risk of developing the disease. However, it seems more likely that this risk is produced by the combined effect of several genes, which interact through different mechanisms to increase a person’s susceptibility to schizophrenia [2].

As to whether schizophrenia is genetic or acquired, the risk among relatives suggests that this pathology is transmitted by the inheritance of a number of genes of minor effect and it is possible the participation of a gene of major effect of recessive inheritance. This inheritance of mutated genes, their cumulative effect and the effect of the environment, contribute to the person being more predisposed to the disease. In addition, it is likely to be genetically heterogeneous, i.e., different genes contribute to the same phenotype in different families and populations [1].

In addition to genetic factors in schizophrenia, environmental and situational factors associated with an increased incidence of the disease have been observed to be involved. Some of them would be the area of residence, obstetric complications or infectious factors. People living in urban areas have a 35 times higher risk of suffering from schizophrenia. Obstetric complications such as Rh incompatibility, low birth weight and maternal nutritional deficiencies in the first trimester are also associated with an increased risk of schizophrenia [1].

In 2022, the largest genetic study in relation to schizophrenia has been published, in which 120 genes have been linked to this disease [6]. An example is the DPYD gene, which codes for an enzyme involved in the metabolism of pyrimidines (a type of nucleotide), or the AKT3 gene, which codes for a protein involved in a large number of biological processes, such as cell proliferation and death, glycogen synthesis and glucose uptake, among others. 

 

 

24Genetics health test: learn about the genetic factors of schizophrenia

 

Schizophrenia is among the complex diseases that 24Genetics analyzes in its health test. Through the application of genome-wide association studies (GWAS), the DNA markers of people with a disease are compared to people without that disease. In this way, genetic differences can be identified. 

These studies are very useful for prevention and early diagnosis. The data obtained is the predisposition of the healthy person to develop a certain disease with respect to the rest of the population. This is simply a statistical reference, so it does not imply at any time that the disease will develop. If you want to know how prone you are to suffer from this and other diseases, take our test. You can ask us all your questions without any commitment.

 

Bibliography

[1] Genetics of schizophrenia: advances in the study of candidate genes. Adriana Pacheco and Henriette Raventós – Revista de Biología Tropical vol.52 n.3 [Published: 2004; Accessed: Oct. 2022] Available at: https://www.scielo.sa.cr/scielo.php?script=sci_arttext&pid=S0034-77442004000300007 

[2] Causes of schizophrenia and heritability – Veritas [Published: Feb. 2020; Accessed: Oct. 2022] Available at: https://www.veritasint.com/blog/es/causas-de-la-esquizofrenia/ 

[3] Childhood schizophrenia: What are the early signs? – Dr. Rochelle Caplan (Semel Institute of University of California Los Angeles) [Revised: June 2022; Accessed: Oct. 2022] [4] Childhood Schizophrenia Task Force – Veritas [Published: Feb. 2020; Accessed: Oct. 2022

[4] Psychiatric Genomics Consortium Schizophrenia Working Group. Biological insights into 108 genetic loci associated with schizophrenia. Nature 511 , 421-427 [Published: 2014; Accessed: Oct. 2022]. Available from: https://doi.org/10.1038/nature13595 

[5] What are the different types of schizophrenia? Medical News Today – Jamie Smith; Reviewed medically by Marney A. White, PhD, MS, Psychology [Published: Aug. 2021; Accessed: Oct.2022] Available from: https://www.medicalnewstoday.com/articles/es/tipos-de-esquizofrenia 

[6] Trubetskoy, V., Pardiñas, A.F., Qi, T. et al. Mapping genomic loci implicates genes and synaptic biology in schizophrenia. Nature 604, 502-508 (2022). https://doi.org/10.1038/s41586-022-04434-5 

 

Written by Manuel de la Mata

Geneticist

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