Acceptance was strongly negatively related to cognitive impairment, to the fatigue variables and to depression and anxiety. Descriptive information and correlations between the test variables are presented in Table 2.

Multiple regression models revealed that hypothesis 1 and 2 could be confirmed (see Table 3). In detail, there was a significant negative relationship between acceptance and subjective cognitive impairment (H1) and fatigue (H2). Acceptance explained 26% of the variance of subjective cognitive impairment and 34% of the variance in fatigue. Both effects remained significant when control variables were entered into the model, but the unique effect of acceptance was reduced to 12% and 10%, respectively. Including depression and anxiety further reduced the uniquely shared variance to 1% in both models.

The moderation analyses revealed that the level of acceptance significantly affected the relationship between fatigue severity and fatigue-related impairment (see lower part of Table 3). In detail, main effects of acceptance and fatigue severity were significant. Including the interaction term in the analysis improved the model significantly. Investigating the simple slopes, we found that the relationship between fatigue severity and impairment is significantly weaker when acceptance is high (β=.34, 95%CI [.338/.342]) than when it is low (β=.48, 95%CI [.478/.482]). This moderation effect is displayed graphically in Figure 3.

Figure 3.

Graph displays the relationship between fatigue severity and impairment for individuals with low and high acceptance. Low (high) fatigue severity and acceptance are computed as 1 SD below (above) the mean.

(0.07MB).

While the affective benefit of acceptance has been established in a large number of empirical studies, its benefit regarding cognitive resources has been poorly studied to date. This is the first study examining and supporting the resource-saving benefit of acceptance in a clinical sample.

Confirming hypothesis 1, our results show that acceptance is strongly negatively associated with subjective cognitive impairment. Specifically, one fourth of the variation in subjective cognitive impairment is explained by acceptance. We are aware of one study assessing the impact of emotional acceptance (resembling the construct of acceptance) on subjective cognitive performance (Alberts et al., 2012). Participants were instructed to either accept or to suppress emotions during a sad mood induction task. Accepting individuals performed better on a subsequent cognitive task than individuals suppressing emotions. Merging Albert and colleagues’ study (Alberts et al., 2012) with ours, one may carefully postulate that acceptance requires less cognitive resources and thus is associated with less subjective cognitive impairment. A second argument commending to the usefulness of acceptance for cognitive functioning is that a bunch of studies has shown that practicing meditation (a concept closely related to acceptance) improves cognitive functioning (for review, see Biegler, Chaoul, & Cohen, 2009). This is first evidence pointing to the potential usefulness of ACT-based interventions in order to manage subjective cognitive impairment in cancer survivors. Future research is needed to replicate findings and to investigate the causal effects and underlying mechanisms.

Regarding hypothesis 2, we have shown that acceptance is negatively related to fatigue. Importantly, acceptance explains about one third of the variation in fatigue, which represent large effect sizes according to Cohen's classification (Cohen, 1992). To our knowledge, two social and work psychological studies have shown this effect before (Biron & van Veldhoven, 2012; Kuba & Scheibe, 2017), which were longitudinal studies establishing a causal relationship between acceptance and fatigue. Transferring this association into the population of cancer patients sheds light on new potential targets for intervention. A large number of studies has shown that acceptance can be increased by ACT-based interventions (Graham et al., 2016), which in turn seems to be the crucial mediator for better well-being (Aguirre-Camacho et al., 2017; Feros et al., 2013). Few ACT-based intervention studies have investigated changes in fatigue: very recent pilot results of a telephone-delivered intervention with cancer patients showed moderate reductions in fatigue after the intervention and at 12-months-follow-up compared to small reductions in the active control group (Mosher et al., 2018). Conversely, however, results of an earlier telephone-delivered ACT-based intervention study did not find an intervention effect on fatigue at 6 and 12 months (Hawkes, Pakenham, Chambers, Patrao, & Courneya, 2014). There is one multiple single-case designed study (Roche, Dawson, Moghaddam, Abey, & Gresswell, 2017) and one intervention trial (Jacobsen, Kallestad, Landrø, Borchgrevink, & Stiles, 2017) assessing the effectiveness of an ACT-based intervention specifically to reduce fatigue in non-cancer patients with chronic fatigue syndrome. Even though in both studies patients had a large reduction in fatigue-scores, Jacobsen et al. (2017) reported no association between acceptance and fatigue. Beyond the scope of ACT-based interventions, cognitive behavioral therapy seems effective in reducing fatigue (Abrahams et al., 2017; Gielissen et al., 2007). However, a long-term follow-up up to 14 years after intervention has shown that half of the patients who had recovered during the intervention phase reported severe fatigue at follow-up (van Gessel et al., 2018). This high rate of relapse has been found in an earlier study with more than 500 fatigue-patients (Janse et al., 2017). Van Gessel et al. (2018) suggest that mindfulness-based interventions may help those patients that experience a relapse. We emphasize the importance of conducting randomized controlled trials to test the effects of ACT on fatigue.

Combining the results of these earlier studies with our findings, acceptance may be a strong target for a psychological intervention in order to reduce subjective cognitive impairment and fatigue in cancer patients. Given that interventions are urgently needed for patients and survivors to deal with these persistent and constraining symptoms (Kreissl et al., 2016), further research and especially randomized controlled trials are needed to test the effectiveness of ACT-based interventions in reducing subjective cognitive impairment and fatigue in cancer patients.

The postulation that psychologically flexible survivors would be less impaired by fatigue severity (H3) was supported in the current sample. This finding supports the theoretical foundations of acceptance, which postulate that refraining from attempting to control unwanted internal states reduces their impact on daily life and mental well-being (Hayes et al., 1999). The findings dovetail earlier research showing that participants with higher levels of acceptance were less affected by increased life stress (Kuba & Scheibe, 2017; Shallcross, Troy, Boland, & Mauss, 2010, study 2).

The results of the present study should be interpreted in lights of its limitations: First, the moderate response rate may have led to a biased participant group, which may for example be more or less burdened than the complete population of hematologic cancer survivors. However, a subsample of participants (N=138) provided reasons for study denial including physical burden (13%) and “feeling too well” (14%). It thus seems that particularly burdened patients as well as particularly well patients refrained from study participation at a same rate leveling each other out. A second limitation is the cross-sectional study design. Even though due to the nature of the statistical tests we used directive language in the results section, we cannot draw conclusions about the causal effect of acceptance. Future research my overcome this limitation by implementing longitudinal and experimental studies.

We have shown that acceptance is strongly negatively associated with fatigue and subjective cognitive impairment. Because consequences of cancer like fatigue and subjective cognitive impairment cannot always be avoided or treated medically, we showed that a protecting factor may be the manner in which emotions and cognitions are processed. Survivors who habitually have higher levels of acceptance seem to show fewer symptoms of fatigue and subjective cognitive impairment. Given that acceptance can be increased by ACT-based interventions, a new potential target for a psychological intervention has opened up in order to deal with these symptoms.

A second important finding is that survivors who have a habitual tendency to accept emotions and cognitions and maintain current goal pursuit seem well-equipped to maintain functioning in daily life even when confronted with symptoms of fatigue. Findings highlight the suitability of ACT- interventions for medical conditions when suffering can be limited even when the symptom itself may not be reduced.

ACT-based interventions may be tailored to the special circumstances of patients with fatigue and subjective cognitive impairment. However, given that ACT follows a holistic and transdiagnostic approach, future research may investigate whether a general ACT-approach may already be effective for the wide range of psychosocial consequences following cancer. Finally, while ACT has been delivered in face-to-face consultations (Feros et al., 2013), it has also shown effective in group-settings (Aguirre-Camacho et al., 2017), in self-help formats (Wersebe, Lieb, Meyer, Hofer, & Gloster, 2018), and newer formats like web-based or telephone-based programs (Hawkes et al., 2014; Mosher et al., 2018; Pots et al., 2016). These are often economically more cost-efficient, have a lower threshold for participation and can be delivered to patients at home (Heber et al., 2017). As such, ACT may constitute an effective and efficient intervention to increase levels of acceptance and thus reduce suffering from fatigue and subjective cognitive impairment. While its effect on fatigue has been investigated in a few attempts, its effect on subjective cognitive impairment has never been studied. We emphasize the importance of conducting randomized controlled trials that assess the impact of this format on (long-term) effects of cancer like fatigue and subjective cognitive impairment.

We thank all survivors who participated and Philipp Göbel for helping us to collect the data. We acknowledge support from the German Research Foundation (DFG) and Leipzig University within the program of Open Access Publishing. The work was supported by the Deutsche José Carreras Leukämie-Stiftung e.V. [grant number DJCLS R 14/18]. The funding source had no involvement in the study design, collection, analysis and interpretation of data.