The Mediating Effects of Physical Symptoms on the Relationship between Distress and Posttraumatic Symptoms in Cancer Patients

Background and Purpose: Research is beginning to show a link between distress and increased levels of posttraumatic stress symptoms (PTSS).  Evidence indicates that sustained distress and PTSS results in numerous negative outcomes in both mental and physical health.  Understanding the mechanisms by which distress results in, or influences, PTSS will aid clinicians in developing protocols to more effectively identify PTSS in cancer patients. The hypotheses for the study were that 1. higher levels of distress would be related to higher levels of PTSS; 2. the number of physical symptoms would mediate the hypothesized relationship between distress and PTSS, and 3.  age and social support would moderate the direct and mediated relationships.

Methods: Survey data were collected during intake at nineteen cancer centers across the continental United States (n=1,119).  Patients reported distress ratings on the National Comprehensive Cancer Network (NCCN) Distress Thermometer (DT), responded to questions related to PTSS, and provided information about current symptoms and social support systems.  Hypotheses were tested using a conditional process model in the PROCESS macro for SPSS. Paths were analyzed for direct and indirect effects, including mediation, moderation and mediated moderation. Bootstrap confidence intervals (5,000 samples) were used to indicate significant conditional effects.

Results: Findings indicated that, while distress scores were influential in the total model, the direct effect of distress on PTSS was negated by the model’s indirect effects.  Furthermore, the effects of social support (b = -.091, t(1109) = -3.09, p = .002) and age (b = -.115, t(1109) = -4.12, p<.001) were independent protective factors and there was a moderation effect that varied across groups.  Lastly, the addition of a mediator variable representing physical cancer symptoms helped explain the relationship between distress and PTSS (b = -3.171, t(1109) = -8.48, p<.001). Analysis of the conditional effects indicated that younger cancer patients with lower levels of social support were most likely to be negatively impacted by increased physical symptoms.

Conclusions and Implications: Findings support previous research, which suggest that distress levels and PTSS are related, and age and social support are may moderate this relationship. These findings add to the growing knowledge base by providing evidence for a potential mechanism by which distress relates to PTSS.  Furthermore, the findings suggest that age and social support may be protective factors for certain groups and risk factors for others.  Findings from this study provide formative data to suggest potential next steps that could lead to improvements in routine psychosocial screenings in cancer treatment settings, thus increasing the likelihood of intervening earlier with patients.