Objective. Life, following curative treatment, can be a struggle for former cancer patients. In this phase of their illness, social comparison information may help to improve a patient's quality of life (QOL). The objective of this study was to determine whether the effects of this information depend on the following two variables: (1) the individual's physical health and (2) the individual's sensitivity to social comparison.

Design. In the current study, the effects on a patient's QOL were tested that occur when they are listening to a psychological oncological expert talking about cancer patients’ experiences. Three different recorded interviews with experts were compared (on negative emotions, effective coping, or both), and individual differences were tested as moderators. In addition, the expert source conditions were compared with a condition in which the source was not an expert but a former patient.

Methods. In a randomized field experiment, 154 Dutch former cancer patients (Mage= 55 years; 68% women) were assigned to one of the four conditions (three expert source and one former patient source condition). QOL was assessed after 2 months.

Results. The effects of the expert source conditions on QOL depended on the participants’ physical health (good vs. poor) and on the participants’ sensitivity to social comparison (whether the recipient reacts with contrast or identification), as indicated by significant three-way interactions (p < .001). Depending on these two variables, one of the three expert source conditions was at least as effective as the former patient source condition.

Conclusions. The results show that desired and undesired effects are found when individual differences relevant to the processing of intervention information are examined.

Statement of contribution

What is already known on this subject? 

It is known that social comparison processes are important determinants of emotions and QoL. In addition, research has shown that QoL in (former) cancer patients is lowered and interventions are needed.

What does this study add? 

This study showed that the application of social comparison as a method to increase QoL in cancer patients can be beneficial: It showed that applying the auditory channel, in which the expert source becomes more prominent, is effective. In addition, the study illustrates that psycho-social interventions can have side-effects; a phenomenon that has hardly been addressed in the literature and in practice.