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Twin Res Hum Genet. 2014 Jun;17(3):164-76. doi: 10.1017/thg.2014.12. Epub 2014 Apr 15.

The Roots of Autism and ADHD Twin Study in Sweden (RATSS).

Author information

Center of Neurodevelopmental Disorders at Karolinska Institutet,Pediatric Neuropsychiatry Unit,Department of Women's and Children's Health,Karolinska Institutet,Stockholm,Sweden.
Department of Clinical Neuroscience,Karolinska Institutet,Stockholm,Sweden.
MRI Research Center,Neuroradiology Clinic,Karolinska University Hospital,Stockholm,Sweden.
Human Genetics and Cognitive Functions,Institut Pasteur,Paris,France.
Department of Clinical Genetics,Karolinska University Hospital,Stockholm,Sweden.
Department of Neuroscience,Karolinska Institutet,Stockholm,Sweden.
Physiology and Behavior Laboratory,Swiss Federal Institute of Technology (ETH) Zurich,Switzerland.
Department of Biosciences and Nutrition,Karolinska Institutet,Huddinge,Sweden.
Section of Psychiatry and Neurochemistry,Sahlgrenska Academy,Gothenburg,Sweden.
Public Health Epidemiology,Department of Public Health Sciences,Karolinska Institutet,Stockholm,Sweden.
Centre for Brain and Cognitive Development,Department of Psychological Sciences,Birkbeck,University of London,London,UK.
Neuroscience and Physiology,Forensic Psychiatry,University of Gothenburg,Gothenburg,Sweden.
Department of Medical Epidemiology and Biostatistics,Karolinska Institutet,Stockholm,Sweden.


Neurodevelopmental disorders affect a substantial minority of the general population. Their origins are still largely unknown, but a complex interplay of genetic and environmental factors causing disturbances of the central nervous system's maturation and a variety of higher cognitive skills is presumed. Only limited research of rather small sample size and narrow scope has been conducted in neurodevelopmental disorders using a twin-differences design. The Roots of Autism and ADHD Twin Study in Sweden (RATSS) is an ongoing project targeting monozygotic twins discordant for categorical or dimensional autistic and inattentive/hyperactive-impulsive phenotypes as well as other neurodevelopmental disorders, and typically developing twin controls. Included pairs are 9 years of age or older, and comprehensively assessed for psychopathology, medical history, neuropsychology, and dysmorphology, as well as structural, functional, and molecular brain imaging. Specimens are collected for induced pluripotent (iPS) and neuroepithelial stem cells, genetic, gut bacteria, protein-/monoamine, and electron microscopy analyses. RATSS's objective is to generate a launch pad for novel surveys to understand the complexity of genotype-environment-phenotype interactions in autism spectrum disorder and attention-deficit hyperactivity disorder (ADHD). By October 2013, RATSS had collected data from 55 twin pairs, among them 10 monozygotic pairs discordant for autism spectrum disorder, seven for ADHD, and four for other neurodevelopmental disorders. This article describes the design, recruitment, data collection, measures, collected pairs' characteristics, as well as ongoing and planned analyses in RATSS. Potential gains of the study comprise the identification of environmentally mediated biomarkers, the emergence of candidates for drug development, translational modeling, and new leads for prevention of incapacitating outcomes.

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