By Rosa Martínez, University of Barcelona Press
Image: From left to right, researchers Miquel Casas, Marta Ribasés, Josep Antoni Ramos-Quiroga and Cristina Sànchez-Mora (Vall d'Hebron Research Institute, VHIR) and Bru Cormand (University of Barcelona). (Photo: VHIR)
Schizophrenia, autism, bipolar disorder, major depressive disorder and attention-deficit/hyperactivity disorder (ADHD) share a significant genetic etiology. More than 300 experts from 250 worldwide institutions collaborate in the research, coordinated by the Psychiatric Genomics Consortium, the largest consortium in the history of psychiatry and the largest biological experiment in psychiatric disorders genetics.
Psychiatric disorders affect a third of population; their causes continue to be quite unknown. The study analyses the genotype of more than 75,000 individuals (patients and control) in order to determine which DNA variations are most commonly associated to five psychiatric disorders: autism, schizophrenia, bipolar disorder, major depressive disorder and ADHD.
In Catalonia, the research is coordinated by Vall d’Hebron Research Institute (VIHR), by means of the International Multicentre Persistent ADHD Genetics Collaboration (IMpACT), which analyses the genetic causes of ADHD, a disorder that is characterized by significant problems either of inattention and/or hyperactivity and impulsiveness, that affects children and adults and that occurs more frequently in males.
Bru Cormand, from the Department of Genetics and the Institute of Biomedicine of the University of Barcelona (IBUB) and member of the consortium IMpACT, explains that “these psychiatric disorders share some clinical manifestations which may indicate that there is a common genetic basis. These disorders are quite common in population, they have been widely studied in an independent way by scientific groups, and this is the first time that a huge study confirms their genetic correlation”.
Variability Due to Single-Nucleotide Polymorphism
The research analyses changes in the so-called ‘single-nucleotide polymorphism’ (SNP), the most common changes in human genome. This is the first scientific publication based on genome-wide association studies (GWAS) to examine shared genetic etiology of disorders. According to the research, single-nucleotide polymorphisms (SNPs) explain 17–29% of the variance in liability. Therefore, psychiatric disorders may be part of the same etiological spectrum. SNP-based heritability for schizophrenia patients is 23%; for bipolar disorder patients is 25%; for major depressive disorder is 21%, for ADHD, 28%, and for autism patients, 17%.
According to Bru Cormand, “70% of variance observed in disorders may be probably explained by genetic or epigenetic variations different from SNPs (for instance, rare genetic alterations which have a strong action on phenotype, variations on the number of copies, etc.) and environmental factors”. “In the case of ADHD”, Cormand explains, “there is plenty evidence that environmental toxins, tobacco and alcohol consumption during pregnancy or psychosocial stress can contribute to the development of the disorder”.
Strong Genetic Correlation Among Disorders
Furthermore, the research published on Nature Genetics identifies that SNP-based genetic correlation is high between schizophrenia and bipolar disorder, and moderate between schizophrenia and major depressive disorder, bipolar disorder and major depressive disorder, ADHD and major depressive disorder, and schizophrenia and ADHD. Results show that broad spectrum symptoms of mental disorders share some risk factors. Consequently, future research must be fostered in order to identify common SNPs and the ones specific to each disorder. Basic research is promoting scientific advances in the field of psychiatric diagnosis.
Bru Cormand affirms that “in the future, to identify the genetic profile of patients with psychiatric disorders will contribute to predict which disorders may affect them; it will be a new tool to improve preventive strategies”. The research is supported by La Marató de TV3, the Spanish Ministry of Economy and Competitiveness, Alicia Koplowitz Foundation and the Centre for Biomedical Network Research on Rare Diseases (CIBERER).
Further information:
http://www.ub.edu/web/ub/en/menu_eines/noticies/2013/09/002.html
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Un código genético es un código que efectivamente, condiciona ciertas cosas, pero el ser vivo que sale depende de muchas más cosas. Es la famosa diferencia entre genotipo y fenotipo. Sin duda, el temperamente tiene una base genética (pero no solo: por ejemplo, el sufrimiento fetal puede cambiarlo) pero después la persona se desarrolla y en él influyen muchas cosas. Un ejemplo: la corteza auditiva se transforma en visual en sorderas congénitas o muy precoces, aunque la causa de la sordera no sea genética. Seguimos con los intentos del positivismo más rancio, versión cientifismo y psicologismo de explicar lo que está vivo por lo muerto. Por ejemplo, un código, aunque la vida utilice códigos, pero por sí mismo no son nada.
Publicado por: nessie | 23/10/2013 12:08:48