The high-impact scientific journal Nature Genetics has published on Tuesday the study with the largest sample of patients affected by obsessive-compulsive disorder (OCD) ever analyzed, which has made it possible to identify multiple DNA variants that could help predict which people are at a higher risk of developing the disease and which are the best treatments to deal with it.
The study represents a substantial advance in the identification of genetic risk loci (specific locations of chromosomes), with DNA variants being associated with an increased susceptibility to OCD. The researchers have detected 30 independent loci, with 25 genes in these loci, that contribute significantly to the risk of developing the disease.
The study, in which more than 200 researchers from around the world participated, is the culmination of two decades of collaborative effort, which has made it possible to recruit a sample of 53,600 people affected by OCD and more than 2 million healthy controls.
Researchers from IDIBELL and Bellvitge Hospital, part of the International Psychiatric Genomics Consortium (PGC), have participated in the study including samples from more than 700 patients diagnosed and treated in the hospital’s OCD program in the last 20 years.
Genomics clarifies the complexity of OCD
OCD is a disease that affects 2-3% of the population and begins in early stages of life, often leading to severe functional deterioration in all areas of life (family, academic, work and social). It is characterized by the presence of obsessions (intrusive, involuntary and repetitive thoughts, images or impulses, which generate discomfort) and compulsions (manifest or mental behaviors aimed at reducing this discomfort). Current treatments include different combinations of drugs and cognitive-behavioral therapy, as well as neuromodulation techniques in severe and refractory forms.
Now, with the new data provided by the study, a broader perspective of what OCD is can be configured. In this sense, Dr. María del Pino Alonso, principal investigator of the Psychiatry and Mental Health research group at IDIBELL and head of the Psychiatry Service at Bellvitge Hospital, who has participated in the project, highlights that the findings of the study “confirm that OCD is not a disease caused by a single gene or alteration of a single brain region, but a disease in which hundreds or thousands of genes and complex brain circuits are involved, whose interaction contributes to the development of the disease.”
In fact, thanks to the analysis of the relationship between the expression and function of multiple genes and the risk of suffering from OCD, it has been possible to detect up to 25 of these genes distributed in 30 regions of the genome involved in the disease. Dr. Alonso points out that these genes are especially expressed in certain neurons and areas of the brain related to decision-making, memory and higher-order cognitive functions. Thus, the risk of suffering from OCD, according to the study, is associated, among others, with some genetic variants expressed in neurons rich in dopamine receptors in the hippocampus and cortical regions.
Relationship with other disorders and future research
The study also shows that OCD is a disease genetically related to other mental disorders such as Tourette’s syndrome (a disorder due to motor and phonic tics), anorexia nervosa, anxiety and depression.
The results of the study are important, concludes Dr. Alonso, because “they help us understand the complexity of OCD, a disease resulting from the interaction between genetic risk factors and environmental factors, such as hormonal factors, for which we do not yet have a curative treatment. Understanding how risk genes are expressed in certain brain regions can help us develop new, more effective treatments and even implement prevention strategies in populations at high risk of developing OCD.”
The next steps in this area of research will be aimed at detecting additional genes associated with the risk of suffering from OCD and deepening the knowledge about the shared genetic risk of OCD with other neurological and psychiatric disorders.
The Bellvitge Biomedical Research Institute (IDIBELL) is a research centre created in 2004 and specialising in cancer, neuroscience, translational medicine and regenerative medicine. It has a team of more than 1,500 professionals who, from 73 research groups, publish more than 1,400 scientific articles a year. L’IDIBELL is participated by the Bellvitge University Hospital and the Viladecans Hospital of the Catalan Health Institute, the Catalan Institute of Oncology, the University of Barcelona and the City Council of L’Hospitalet de Llobregat.
IDIBELL is a member of the Campus d’Excelencia Internacional of the University of Barcelona HUBc and is part of the CERCA institution of the Generalitat de Catalunya. In 2009 it became one of the first five Spanish research centres accredited as a health research institute by the Carlos III Health Institute. In addition, it is part of the HR Excellence in Research program of the European Union and is a member of EATRIS and REGIC. Since 2018, IDIBELL has been an Accredited Centre of the AECC Scientific Foundation (FCAECC).