Unequal opportunities for quality of life? The influence of social status and symptoms in routine psychotherapeutic care

The project is a secondary data analysis of the multicenter TONI trial (PsyTOM), which investigated the effectiveness of blended psychotherapy in routine outpatient care in Germany. The master’s thesis focuses not on treatment arm effects, but on understanding how symptom burden, subjective social status, and health‑related quality of life (HRQoL) are interrelated at the beginning and over the course of psychotherapy. The overarching goal is to clarify whether patients with lower social status have systematically poorer quality of life, even when they achieve comparable symptom reduction, and to what extent social status shapes the association between symptoms and HRQoL in everyday clinical practice. Conceptually, the project builds on the distinction between general Quality of Life (QoL) and Health‑Related Quality of Life (HRQoL). HRQoL is defined as the subjectively perceived level of functioning in physical, psychological, and social domains. In line with this definition, HRQoL will be operationalized using the AQoL‑8D, which provides a sensitive, multidimensional measure of health‑related quality of life suited to psychotherapy research. Symptom burden is captured as a composite of depressive and anxiety symptoms (PHQ‑8 and GAD‑7), reflecting global mental distress. Subjective social status (SSS) is assessed with the German version of the MacArthur ladder, emphasizing participants’ perceived position in the social hierarchy and thus capturing a psychologically meaningful aspect of socioeconomic status. The study has four main aims. First, it will describe the level and distribution of HRQoL in a large, naturalistic outpatient sample at the start of treatment (t0), including relevant subscales (e.g., Mental Health, Relationships, Coping, Independent Living). Second, it will examine cross‑sectional associations between symptom burden, SSS, and HRQoL at baseline by means of multiple linear regression models that control for age (including a quadratic term to account for potential U‑shaped age effects), gender, and migration background. On this basis, the first hypothesis tests whether higher symptom burden is associated with poorer HRQoL; the second hypothesis tests whether SSS explains additional variance in HRQoL beyond symptoms and sociodemographic covariates. Third, the project will analyze change over the course of therapy from baseline (t0) to six months (t3). Paired‑samples t‑tests and effect sizes (Cohen’s d) will be used to quantify improvements in HRQoL, and change scores will be computed for both HRQoL and symptom burden. Correlational and regression analyses of these change scores will address whether the magnitude of symptom reduction is systematically related to improvements in HRQoL. This is theoretically important because prior work suggests that HRQoL does not always improve in lockstep with symptom relief and may remain impaired even after remission. Fourth, the project includes exploratory mediation analyses to examine potential mechanisms linking social status, symptoms, and HRQoL. Drawing on stress and resource theories (e.g., social defeat, reserve capacity model), it is hypothesized that lower SSS is associated with higher symptom burden, which in turn impairs HRQoL, and that patients with higher SSS may benefit more from psychotherapy because they have greater psychosocial resources to translate symptom reduction into restored functioning and quality of life. Cross‑sectional and longitudinal mediation models will therefore test whether symptom burden and changes in symptoms mediate the effects of SSS on HRQoL and its improvement. Because indirect effects and multiple imputation are involved, bootstrapping‑based methods suitable for imputed datasets will be applied. Methodologically, the project uses patient‑reported outcome data from N ≈ 1,150 adults in routine outpatient psychotherapy, irrespective of specific diagnoses, which maximizes ecological validity and generalizability to real‑world care. Analyses will be conducted in R, with careful attention to missing‑data handling (multiple imputation with MICE), regression assumptions, and correction for multiple testing (Holm‑Bonferroni within families of HRQoL outcomes). Covariates include age, gender, and migration background, given their known associations with both mental health and quality of life. Expected outcomes include: - Confirmation of a strong negative association between symptom burden and HRQoL at baseline. - Evidence that subjective social status explains unique variance in HRQoL over and above symptoms and sociodemographic factors, indicating that social inequalities are reflected not only in symptom levels but also in quality of life. - Robust improvements in HRQoL during psychotherapy, but with only partial overlap between symptom change and HRQoL change, highlighting HRQoL as an independent outcome dimension. - Initial evidence that the relationship between social status and HRQoL is at least partly mediated by symptom burden and/or its reduction, consistent with stress‑ and resource‑based models. Taken together, the project aims to contribute to a more nuanced understanding of therapeutic outcomes in routine care by moving beyond symptom reduction alone and integrating patients’ social context. The findings are expected to inform both research and clinical practice by underscoring the importance of monitoring HRQoL and considering subjective social status when evaluating treatment success and planning interventions for socially disadvantaged patients.