Sampling problems in twin research.
Sampling problems related to twin problems may be of at least three kinds: small samples, self-selection and unrepresentative ascertainment. The article mostly discusses the third type of sample problem. Data from a nationwide Norwegian twin study show that the results of twin studies will be quite different depending upon the ascertainment procedure. According to both the ICD-9 as well as the DSM-III classification system, only samples ascertained from mental hospitals treating severe cases are able to demonstrate hereditary factors of any strength.
Center for Research in Clinical Psychology, University of Oslo, Norway.
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Torgersen
D001008:Anxiety Disorders / Q000235:genetics; D003866:Depressive Disorder / Q000235:genetics; D004200:Diseases in Twins; D006801:Humans; D001523:Mental Disorders / Q000235:genetics*; D019964:Mood Disorders / Q000235:genetics; D012307:Risk Factors; D012494:Sampling Studies; D013001:Somatoform Disorders / Q000235:genetics