1972
DOI: 10.1111/j.1469-1809.1972.tb00767.x
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The use of multiple thresholds in determining the mode of transmission of semi‐continuous traits*

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Cited by 361 publications
(179 citation statements)
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“…For genetic analysis of the dichotomous data (drug use, abuse/dependence), tetrachoric or liability correlation coefficients were calculated (Neale and Cardon, 1992). Liability to drug abuse/ dependence is an estimate of the magnitude of prevalence of the diagnosis among co-twins of affected probands compared to prevalence in the general population (Reich et al, 1972). Under the influence of multiple genes in combination with multiple environmental factors, liability is normally distributed.…”
Section: Discussionmentioning
confidence: 99%
“…For genetic analysis of the dichotomous data (drug use, abuse/dependence), tetrachoric or liability correlation coefficients were calculated (Neale and Cardon, 1992). Liability to drug abuse/ dependence is an estimate of the magnitude of prevalence of the diagnosis among co-twins of affected probands compared to prevalence in the general population (Reich et al, 1972). Under the influence of multiple genes in combination with multiple environmental factors, liability is normally distributed.…”
Section: Discussionmentioning
confidence: 99%
“…By adopting an ordinal model-fitting approach we specified a threshold to separate 'normality' from 'pathology' upon the traits under study. This approach assumes phenotypic discreteness (or semi-continuity) of traits imposed upon of the same normally distributed underlying multi-factorial continuum of risk [39]. As such, it is the closest approximation to the classical medical distinction between affected and unaffected subjects while assuming a multi-factorial underlying liability, whereby several environmental and genetic determinants add to each other to influence the manifestation of an illness once a critical threshold is reached (see Fig.…”
Section: Model Fitting Analysesmentioning
confidence: 99%
“…The observed discontinuous phenotype is therefore conceptualized as the visible manifestation of some underlying, quantitative physiological trait (Falconer, 1989). In principle any number of phenotypic classes can be subsumed in a liability threshold model (Reich et al 1972(Reich et al , 1979Gianola & Foulley, 1983;Morton et al 1991), but diseases involving two phenotypic states and a single liability threshold are typical in human genetic studies-individuals whose liability is below the threshold value are 'unaffected', and those whose liability exceeds the threshold value exhibit the 'affected' condition.…”
Section: Liability and Thresholdmentioning
confidence: 99%