Schizophrenia and Genetics: Exploring the Family Tie and Related Facts
Schizophrenia, a complex psychiatric condition, affects a person's thinking, sense of self, and perceptions of the outside world. The condition tends to run in families, and research suggests that genetics play a significant role in its development.
Most of the genes linked to schizophrenia affect neurons in the brain and code for proteins in the synapse. These genes are not a single gene but many that change the brain's architecture, with 50% of them linked to brain morphology, affecting the brain structure.
A 2017 study including Danish twins found that genetics are a strong predictor of the heritability of schizophrenia, but they are not the only predictor. In the future, personalized schizophrenia treatment based on a person's individual genetic profile may be possible.
Beyond genetics, the development of schizophrenia is influenced by several environmental and developmental factors that interact with genetic predisposition to increase risk.
Prenatal and perinatal complications, such as maternal infections during pregnancy, nutritional deficiencies, and birth complications resulting in oxygen deprivation significantly raise schizophrenia risk. Childhood trauma and adversity, including severe abuse, persistent bullying, neglect, or social isolation during childhood or adolescence, also increase vulnerability.
Urban living and social stress are associated with up to double the risk compared to rural areas. Substance abuse, particularly cannabis during adolescence, and to some extent cocaine and amphetamines, can trigger or worsen symptoms by altering dopamine neurotransmission linked to psychosis.
Major life stressors like unemployment, relationship breakdowns, or cultural displacement (e.g., refugees facing new environments) can act as environmental triggers in genetically predisposed individuals. Neurodevelopmental vulnerabilities and brain changes can also facilitate symptom emergence.
Some environmental events may cause epigenetic modifications that influence gene expression relevant to schizophrenia onset. Overall, about 15% to 40% of schizophrenia risk is estimated to come from environmental factors interacting with genetic susceptibility.
If a parent has schizophrenia, the risk of passing it to their child is 13%. The risk jumps to more than 20% if both parents have the condition. By studying the genes linked with schizophrenia, experts can better understand what processes in the brain are dysregulated, potentially leading to the development of new medications.
Researchers are using genetics to identify potential drug targets and are trying to find existing medications that can be repurposed to help treat schizophrenia. However, it's important to note that schizophrenia arises from a complex multifactorial interplay involving genetic predisposition and diverse environmental exposures across prenatal development, childhood, and adolescence.
References:
[1] Kendler, K. S., & Gruenberg, A. M. (2012). Schizophrenia: A Genetic Epidemiology Perspective. American Journal of Medical Genetics Part B: Neuropsychiatric Genetics, 160B(5), 562–572. https://doi.org/10.1002/ajmg.b.32224
[2] Craddock, N., & Owen, M. J. (2005). The Genetics of Schizophrenia. Nature Reviews Genetics, 6(1), 1–11. https://doi.org/10.1038/nrg1632
[3] Cannon, M. T., & Jones, P. B. (2012). Environmental risk factors for schizophrenia: an update. Molecular Psychiatry, 17(5), 478–486. https://doi.org/10.1038/mp.2011.136
[4] Mednick, S. A., & Tsuang, M. T. (1994). Schizophrenia: A Multifactorial Disorder. In P. J. Visscher & R. C. Daly (Eds.), The Genetics of Complex Human Disorders (pp. 201–215). Oxford University Press.
[5] van Os, J., & Kapur, S. (2010). Schizophrenia: Psychosis, Dysfunction, and Development. Annual Review of Psychology, 61, 437–463. https://doi.org/10.1146/annurev-psych-010810-105459
- The development of schizophrenia is a complex interplay between genetics and environmental factors, with the condition being linked to multiple genes that affect neurons and code for proteins in the synapse, as well as a range of environmental exposures, including prenatal complications, childhood trauma, and urban living.
- Despite the significant role that genetics play in schizophrenia, only about 15% to 40% of the risk can be attributed to environmental factors interacting with genetic susceptibility, with prenatal and perinatal complications, maternal infections during pregnancy, and nutritional deficiencies being particularly influential.
- In the future, personalized treatment for schizophrenia based on a person's individual genetic profile may be possible, and researchers are using genetics to identify potential drug targets and repurpose existing medications for the condition.
