Social Support Source and Effectiveness Are Associated with Distress Among Hematopoietic Stem Cell Transplant Survivors Experiencing Stress Due to Negative Life Events after Treatment

Hematopoietic stem cell transplant (HSCT) survivors face a variety of stressful challenges in the months and years after treatment including risk for disease relapse, transplant failure, and late effects of treatment; chronic symptoms and complications; and the need to adhere to continuing medical management. Layered on treatment-related challenges are treatment- and non-treatment-related financial, family, work, or other psychosocial strains. Research suggests that these kinds of "life event stressors" can cause psychological distress, which in turn may influence survivors' health behaviors and clinical outcomes. Receiving effective social support from a caregiver has been associated with lower distress (main effects), and the effectiveness of caregiver support could also be an important determinant of whether the support mitigates or "buffers" adverse effects of life event stressors. We applied our Social Support Effectiveness framework to investigate whether: (1) the effectiveness of social support from a partner or non-partner caregiver was associated with survivor distress (main effect); (2) the effectiveness of caregiver support was associated with the association between life event stress and distress among survivors (buffering); and (3) whether buffering effects depended on the source of support (partners versus non-partner caregivers).

As part of a larger study, 264 adults who had undergone HSCT 9 months to 3 years previously completed measures of caregiver social support effectiveness (SSE), distress, life event stress, and sociodemographic and medical variables. Life event stress was a count of negative life events experienced in the prior 6 months, measured with a validated scale and scored using recommended procedures. The SSE measure assesses survivors' appraisals of the extent to which social support they receive from their partner or non-partner caregiver generally approximates their needs in terms of its quantity (i.e., it is not too much nor too little) and quality (i.e., it is the right "type" of support, provided skillfully, is not hard to get or is provided without having to ask for it, and does not cause the survivor to feel bad for needing or getting it). SSE is theorized to be a stable feature of support in dyadic relationships (such as those with a partner or family member), with little change over time. Survivors in a committed romantic relationship reported the effectiveness of support received from their partner and those not in a committed relationship reported the effectiveness of support received from their most important transplant caregiver. Hierarchal linear regression was used to evaluate a three-way interaction between life event stress, caregiver SSE, and source of support (partner versus non-partner caregiver) on distress in these cross-sectional data.

In models controlling for covariates, main effects revealed that having greater life event stress (B=0.04; 95% CI 0.04, 0.05; p <0.001) and receiving less effective caregiver support (B=-0.01; 95% CI -0.01, -0.003; p <0.001) were independently associated with greater survivor distress. These main effects were qualified by a 3-way interaction of life event stress, caregiver SSE, and source of support (B=-0.003; CI:-0.004, -0.002; p <0.001). When support was provided by a partner caregiver, higher life event stress was associated with greater distress when partner SSE was low (B=0.03, SE=0.01, p=0.02). There was no association between life event stress and distress when partner SSE was average (B=0.04, SE=0.01, p=0.26) or high (B=-0.003, SE=0.01, p=0.87). Among non-partnered cancer survivors, there was a positive association between life event stress and distress regardless of non-partner caregiver SSE. Thus, effective support from a partner caregiver buffered adverse effects of life event stress on survivor distress, but this salutary effect was not observed for non-partner caregivers.

Our findings are consistent with evidence showing that the effectiveness of caregiver support is an important correlate of distress after HSCT. They extend that work by showing that effective support from a partner caregiver (but not a non-partner caregiver) can mitigate or "buffer" adverse effects of negative life events experienced after HSCT. Findings highlight a need for additional research among HSCT recipients who rely on caregivers other than a partner.