Dyadic coping and social support: Various types of support in hematooncological patients and their spouses—Associations with psychological distress

Patients and spouses use various support strategies to deal with cancer and its associated burden. Support can be perceived within the dyad [perceived dyadic coping (PDC)] or from others [perceived social support (PSS)]. The present study investigates the association of PDC and PSS with depression and anxiety symptoms experienced by hematooncological dyads.


| BACKGROUND
Cancer affects patients and their spouses with a variety of psychosocial and emotional burden. 1 Hematological cancer is often highly aggressive, life-threatening and thus necessitates prolonged and intensive treatments, which can be extremely exhausting. 2 Therefore, patients with hematological cancer and their spouses may report higher levels of psychological distress compared to other cancer populations. 3,4 Up to 27% (17%) of hematological cancer survivors suffer from anxiety (depression) disorder 5 and up to 44% (27%) of their spouses. 4 Although evidence suggest that patients and spouses are interdependent in physical and mental health, 6,7 the majority of studies capture the individual instead of the dyadic level.
For coping with a persistent stressor (like cancer) and the associated burden, patients and spouses rely on a diverse range of support and coping strategies: individual coping, dyadic coping (DC), social support from friends and family and professional support. 8,9 Bodenmann describes a stress-coping-cascade model that includes different coping and support forms applied in sequence. 10 It is supposed that after the onset of stress, people start with individual coping, and in case of prolonged stress, they seek out for other support resources such as DC, social support or professional support. In most cases, different support types can occur simultaneously, especially in continuing and cumulating stressful situations. 10,11 To date, usually individual coping and DC are considered together in research, 12,13 while a study regarding breast cancer also includes social support from others. 14 Overall, studies that examine different forms of support together are scarce.
Research concerning perceived support from the other partner [perceived dyadic coping (PDC)] and its association with psychological distress on a dyadic level in cancer population are scarce. A study with couples facing prostate cancer found no associations between perceived supportive DC and common DC with distress, but a positive association between perceived negative DC and distress in both, 15 while a study with breast cancer couples report an association with common DC, an less depression symptoms. 16 Furthermore, a study with breast cancer couples reports only a significant association of perceived spousal support of healthy spouses and less anxiety in patients (partner effect) and no associations with own levels of distress. 14 Additionally, individual research with cancer survivors reports significantly lower levels of depression in patients if they perceive high support from their spouses. 17 Perceived social support (PSS) has repeatedly been associated with psychosocial outcomes in cancer patients and their spouses.
Decreased quality and quantity of PSS are associated with increased depression symptoms and stress in breast cancer survivors. 18 A negative association between PSS and psychological distress has been identified by other studies in different cancer populations. 8,14,19 This association was also evident in spouses, although they report lower levels of support from family and friends. 14 It should be noted that the provider of PSS is not specified in some studies 8,18,19 ; therefore, it can include family and friends as well as spouses.
The present study aims to examine the association of different support forms with psychological distress experienced in hematological cancer dyads. First, it will be examined whether patients and their spouses differ regarding psychological distress, PDC and PSS.
While this question has been addressed in other cancer populations, 14,15 evidence at the level of dyads is hitherto still scarce, especially with regard to PSS in couples facing hematological cancer.
Second, our study will examine to which extent PDC and PSS reported by patients and spouses are related to their psychological distress, considering the interdependence of the dyadic data. Based on the assumption that different support forms are used simultaneously in situations with a persistent stressor, PDC and PSS are simultaneously included in the analysis. Since research in this area regarding cancer population is scarce, the present analysis has explorative character and aimed to more thoroughly explore the association between PDC and psychosocial distress in a comparably large sample of patient-spouse dyads. Adding to previous research, 8,14,18,19 we hypothesize that more PSS would be associated with less depression and anxiety symptoms in patients and their spouses.

| Sociodemographic and clinical data
Sociodemographic variables were assessed via self-report. Medical characteristics were extracted from patients' medical records.

| Perceived social support
The ENRICHED Social Support Instrument (ESSI) is a valid and reliable instrument for assessment of PSS. 21 The five items (e.g., 'Is there someone available to give you good advice about a problem?') are rated on a five-point scale from 1 to 5 ('at no time' to 'always').
Higher values indicate higher PSS while values below 18 (sum score range from 5 to 25) indicate lack of PSS. 21 The internal consistency of the scale is Cronbach's α = 0.93. In our sample the internal consistency is equal (patients: α = 0.93; spouses: α = 0.94).

| Psychological distress
Psychological distress is assessed with the screening scale Patient Health Questionnaire-4 (PHQ-4). 22 It consists of a two-item depression scale (PHQ-2) and a two-item anxiety scale (GAD-2).
The items are rated on a four-point Likert scale from 0 to 3 ('not at all distressed' to 'nearly every day distressed') related to distress of the last two weeks (e.g., 'Feeling down, depressed ore hopeless over the last two weeks'). A cut-off score of ≥3 in PHQ-2 and GAD-2 indicates elevated scores of depression and anxiety symptoms. In regard to the small number of items the internal consistencies are adequate with α = 0.78 for PHQ-2 and α = 0.75 for GAD-2 in a representative German sample. 23 Internal consistencies in our sample are similar: PHQ-2 α = 0.77 (patients) and α = 0.76 (spouses) and GAD-2 α = 0.76 (patients) and α = 0.75 (spouses).

| Relationship satisfaction
Relationship satisfaction, a control variable, is assessed with a short version of the 'Partnership Questionnaire' (PFB-K) 24 with nine items on a four-point Likert scale from 0 ('never') to 3 ('very often') (Cronbach's α = 0.84 (patients) and α = 0.85 (spouses)). The following requirements are revised before APIMs are estimated using SEM: (1) test of collinearity with squared multiple BODSCHWINNA ET AL.

| Statistical analyses
-1043 correlation (R 2 > 0.90 imply extreme multivariate collinearity), (2) analysis of multivariate outlier by using the mahalanobis distance statistic with a recommended conservative significance level of p < 0.001, (3)   Demographic and medical sample characteristics are given in Table 1.

| Requirements for actor-partnerinterdependence model calculation
Significant correlations among variables between and within dyad members imply nonindependence on individual level (Table S1). All requirements for SEM are met as followed: (1) The highest R 2 is calculated for PHQ-2 from patients with R 2 = 0.62 and therefore extreme multivariate collinearity is not assumed. (2) Three multivariate outliers were detected. Because of missing values, mahalanobis distance could not be estimated for 13 dyads.
Conduction of analyses with and without outliers does not result in different outcomes. Since it can also be assumed that these participants actually responded more extremely than the remaining sample, no cases are excluded.      In summary, first we found differences in the level of PDC

| Study limitations
Some limitations need to be taken into consideration. Since our variables were measured via self-report survey at home, there is uncertainty about a potential social desirability bias and whether the instruction to fill out the questionnaire alone was followed.

| Clinical implication
Cancer burdens hematological patients and spouses to a comparable extent. Both depression and anxiety symptoms of patients and spouses were related to PDC and PSS. Interventions for F I G U R E 2 Actor-partner interdependence model of anxiety symptoms. Anxiety Symptoms (GAD-2) of patients and spouses are controlled for gender, age and relationship satisfaction of patients and spouses; values on arrows are unstandardized beta coefficients (standardized coefficients are in parentheses); *p<.05, **p<.01, ***p<.001. Abbreviation: DC, dyadic coping; ESSI, ENRICHED Social Support Instrument; GAD-2, Patient-Health-Questionnaire anxiety scale; SC, stress communication hematological couples should draw couples' attention to the strong association between perceived negative DC as well as perceived supportive DC and psychological distress. It has already been assumed that interventions focusing on negative DC behavior could be more beneficial for couples. 15 Since PSS of the spouse was beneficial for both spouses and patients, spouses should be brought more into focus for receiving support. Interventions could highlight the importance of PSS for spouses and encourage spouses to increase their search for support, because this can be also indirectly beneficial for patients.

| CONCLUSION
Hematological cancer patients and their spouses use different forms of support to cope with cancer and the associated psychological distress. Overall more attention should be paid on the PDC, since for example PDC was found to be stronger predictor for relationship satisfaction than own behavior scales. 40 In order to gain a deeper insight of the interplay of support, future research should examine all different forms of support collectively in cancer population.
Furthermore, enhancement of PSS should be focused, as PSS is beneficial for both patients and spouses.