Population attributable risk proportions (PARPs) were calculated to describe strength of association between predictor disorders and outcome disorders. PARPs are the proportions of outcome disorders that would not have occurred in the absence of predictor disorders under the model if the survival coefficients represent causal effects. The proportions were calculated by generating a conditional predicted probability of first onset of each outcome disorder at each year of life of each respondent from the coefficients in the best-fitting survival model twice: once using all model coefficients and then again omitting coefficients for the predictor disorders. The actuarial method (Halli et al., 1992) was used to cumulate conditional predicted probabilities to respondent age at interview. PARP was defined as 1-R, where R represents the ratio of mean cumulative predicted probability in the second specification divided by mean cumulative predicted probability in the first specification.
