Modelling risk profiles of depression symptoms using Cloninger ’ s temperament and character traits : a non-iterative approach to assess linear-by-linear association within ordered contingency tables

Personality is linked to mental illness. The relationship between the seven temperament and character traits (TCIs), (Novelty seeking (NS), Harm Avoidance (HA), Reward Dependence (RD), Persistence (P), Self-directedness (S), Cooperativeness (C) and Self Transcendence (ST)), of Cloninger (1994) and three symptoms of psychological distress, or SCLs (Depression (D), Anxiety (A) and Psychoticism (Psy)) is investigated across gender and shown to have significantly different symptom profiles post treatment. The data used in this study was earlier analysed by Turner, et al. (2003) and comes from patients measured pre and post-treatment from the NZ Christchurch Psychotherapy of Depression Study (Joyce, et al. 2002). In this study we have used the newly developed direct estimation approach (Beh and Davy, 2004 and Zafar et al., 2015) to estimate the linear-by-linear association in two-way tables, within the framework of ordinal log-linear models (OLLMs), with the aim of analysing associations between the TCIs and SCLs. Two non-iterative estimators were considered for this study – the Beh-Davy non-iterative estimator (BDNI) (Beh and Davy, 2004) and the Log non-iterative estimator (LogNI) (Beh and Farver, 2009). The BDNI and LogNI estimation methods provide closed-form estimators which do not require iteration to estimate the linear-by-linear association parameter of OLLMs, unlike their conventional and iterative counter parts, such as the Newton-Raphson and the iterative proportional fitting methods. The estimates obtained from the BDNI and LogNI estimation methods are reported, for pairwise relationships between TCIs and symptoms, along with the standard errors and p-values for males and females for pre and post treatment. Both estimators, BDNI and LogNI, provide estimates which are close to each other. We found significant changing relationships between the seven TCIs and psychological distress symptoms across gender for NS and P post treatment; with both TCIs and SCLs dichotomised by the median. We found statistically significant differences between the BDNI and LogNI estimates for males and females, post-treatment; establishing that higher levels of NS are associated with less D and Psy in males as compared to females. Higher HA is shown to be associated with higher D, A and Psy in males and females, pre and post-treatment. S is found to be negatively related to D, A and Psy for males and in females, pre and posttreatment. P is demonstrated as gender-specific only in the case of D; with less D associated with higher levels of P in males comparison with females post treatment. In addition, we demonstrate the linear-by-linear association between pre-treatment TCI’s and change in depression, anxiety and psychoticism (ΔD, ΔA and ΔPsy), where the change is defined as categorised by the median scores of the (post – pre-treatment) levels. We show that pairwise association between three TCI’s (HA, P and C) and two of our three symptoms of psychological distress, ΔD and ΔPsy, are gender-specific. These results reported agree, in part, with preliminary univariate Generalised Additive Model for Location, Scale and Shape (GAMLSS) models based on the combined pre and post treatment data (Hudson et al., 2015a), which allow for non-linearity between TCIs and symptoms, and for interactions between TCI with gender and time.