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.
Torgersen
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Center for Research in Clinical Psychology, University of Oslo, Norway.
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