Enhancing Social Interaction in Depression (SIDE study): protocol of a randomised controlled trial on the effects of a Cognitively Based Compassion Training (CBCT) for couples

Introduction Positive social interactions (PSIs) and stable relationships can exert substantial benefits on health. However, patients suffering from depression benefit less from these health-promoting effects. Moreover, relationship quality and even partners' health has been found to be negatively affected by depressive symptomatology, which may result in overall impairments in social functioning of a romantic couple. Psychobiological research indicates that these impairments may be accompanied by a maladaptive regulation of the patient's neuroendocrine response to external stressors. Concerning the improvement of social functioning, first studies showed promising results of Cognitively Based Compassion Training (CBCT (R)). However, randomised trials are still scarce. Previous programmes did not involve participation of the patient's romantic partner. Therefore, the present study aims to investigate whether a CBCT (R) programme adapted for couples (CBCT (R)-fC) can improve depressive symptoms, distress, social interaction skills and the neurobiological regulation of stress. Methods and analysis Couples with the female partner suffering from depression will be invited to participate in a pre-to-post intervention assessment on two consecutive days, respectively, involving a standardised PSI task, eye-tracking, ECG recordings, saliva-sampling, blood-sampling and questionnaire data. After baseline assessment, participating couples will be randomised to either a 10week CBCT (R)-fC or to a treatment as usual control condition. The primary endpoint is the reduction of depressive symptoms measured by the Hamilton Depression Rating Scale. Secondary outcomes encompass self-rated depression (Beck Depression Inventory), attention towards the partners face during PSI (eye tracking), stress-related biomarkers (cortisol, -amylase, interleukin (IL)-1 ss/IL-6, heart rate variability), methylation of oxytocin-receptor-genes and serotonin-transporter-genes and self-ratings of psychological constructs such as relationship quality and empathy. Ethics and dissemination Ethical approval has been obtained by the Ethics Committee of the Medical Faculty Heidelberg. Results will be presented in international, peer-reviewed journals and on conferences in the field of clinical psychology and psychiatry. Trial registration number NCT03080025.