A dichotomous total CTQ score was derived solely to illustrate the direction of interaction effects on suicide attempt. A total CTQ score ≥ 1 SD above the mean CTQ score of non-substance dependent/no suicide attempt participants (36.49 (11.67), i.e. ≥48) was designated ‘high trauma’ (N = 290); lower total CTQ scores (<48) were designated ‘low trauma’ (N = 590). This approach has been used in our earlier studies: Enoch et al. (2010) and Roy et al. (2010).
