The major focus of Professor Kendler's research is in the genetics of psychiatric and substance abuse disorders. Two major methodologies are used in this research. The first involves large population based twin samples. In these twins, we address the aggregate role of genetic and environmental factors. We seek to understand how these factors interact and correlate, and how, through development, the vulnerability to psychiatric illness and drug abuse is expressed. I have focused my work with twin samples from Virginia - in particular the Virginia Adult Twin Study of Psychiatric and Substance Use Disorders - but also worked with twin samples from Norway, Sweden and Holland. My work has focused on a wide range of disorders including major depression, anxiety disorders, eating disorders, externalizing behaviors, alcoholism, and drug abuse. I have worked a lot toward understanding the genetic and environmental sources of comorbidity of psychiatric and substance use disorders. Josef Parnas is Professor of Psychiatry at the University of Copenhagen, psychiatric consultant at Psychiatric Center Hvidovre (Copenhagen) and co-founder and senior researcher at the Center of Subjectivity Research, an interdisciplinary research center, integrating philsophy of mind, phenomenology and psychopathology Universirt of Copenhagen, Faculty of the Humanities). Parnas has a long track recored in epidemiological, genetic and psychopathological research in schizophrenia. His research in recent years has mainly dealt with the abnormalities of the structure of experience, especially disorders of self-hood, in the schizophrenia spectrum disorders. Another focus is on the nature of the psychiatric object and psychodiagnostic assessment. He has for many years published on theoretical, phenomenological, and epistemological problems in psychopathology.