This study examined whether cancer caregiving is associated with altered HPA activity in partners of men with prostate cancer. As predicted, cortisol production differed in PC partners and the control group. Specifically, PC partners had lower salivary cortisol production throughout the day compared to women whose mates were medically healthy. This finding is consistent with that of Glover and colleagues (Glover and Poland, 2002
), in which cancer caregivers who reported post-traumatic stress symptoms had lower plasma cortisol levels than controls.
PC partners were more likely to report subthreshold PTSD than women whose spouses were medically healthy. In the majority of cases, these symptoms were related to their partner’s cancer diagnosis. As hypothesized, the presence of PTSD symptoms was associated with lower cortisol production, explaining differences in cortisol patterns between PC partners and controls. When PTSD symptomatology was entered in the mixed model analysis, there was no longer a significant difference in cortisol production between PC partners and controls. Instead, women with subthreshold PTSD had lower cortisol levels than controls.
Low cortisol in PTSD patients may result from enhanced negative feedback inhibition in the pituitary and hypothalamus (Yehuda, 2001
). In addition to facilitating the ability to respond to stressors by providing energy to cells in the body when a threat is detected, cortisol also functions to turn off the stress response by suppressing the further release of cortisol and catecholamines when the negative feedback loop is activated by the amygdala (Yehuda, 2001
Evidence for enhanced negative feedback inhibition in PTSD has been found in studies demonstrating that individuals with this disorder have increased glucorticoid receptor sensitivity to dexamethasone (DST), a substance that mimics the effects of cortisol in the body (Yehuda, 2001
). Following administration of DST, PTSD patients have lower cortisol levels than non-PTSD controls. Consequently, lower cortisol production may disrupt recovery from stress by failing to inhibit corticotrophin releasing factor (CRF) and adrenocorticotropic hormone (ACTH), leading to increased stimulation of the sympathetic nervous system and greater catecholamine production (Yehuda, 2001
). Heightened SNS stimulation might increase the risk for stress-related diseases in individuals with clinically significant symptoms of PTSD. This process may contribute to worse physical health in cancer caregivers. Chronic increases in catecholamine production in response to sympathetic nervous system activation may lead to an overactive inflammatory immune response, increasing the risk for cardiovascular disease, diabetes, as well as rheumatologic and other diseases (Miller et al., 2002
). In light of our findings that partners of men with prostate cancer have lower cortisol production and are more likely to report symptoms of PTSD than controls, future research should explore links between glucocorticoid and catecholamine production, inflammation, and health outcomes in spouses of men with PC.
We also found evidence suggesting that the nature of psychological distress in cancer caregivers plays an important role in determining diurnal cortisol patterns. As hypothesized, MDE and PTSD differentially predicted cortisol patterns in participants. Although PTSD symptoms were associated with lower cortisol across the day, depression was associated with higher cortisol in the evening hours and a flattened diurnal cortisol slope. This may shed light on discrepant findings in the literature concerning cortisol production in cancer caregivers (Cohen et al., 2002
; Glover and Poland, 2002
; Miller et al., 2002
; Rohleder et al., 2009
). Research suggests that in depressed individuals diurnal cortisol tends to be flattened, with higher evening cortisol levels than those of non-depressed controls (Linkowski, 2003
), consistent with our results. Studies finding higher evening cortisol in cancer caregivers have also reported higher depression in this group (Cohen et al., 2002
; Miller et al., 2002
). Thus, greater reports of depressive symptoms may explain flattened diurnal cortisol patterns in some cancer caregivers.
There are several limitations in the current study that should be considered when interpreting these findings. First, this study was conducted on a small community sample and findings need to be replicated in larger samples. Second, the sample of PC partners was made up of a heterogeneous group of women whose mates varied in terms of medical characteristics, including time since diagnosis, PC cancer stage, and type of treatment received. It is possible that these characteristics influenced partners’ psychological well-being and HPA activity. However, given the small sample size in the current study, we were unable to fully explore relationships between these factors and HPA activity. Although follow-up analyses suggested that partners of later stage cancer patients had higher distress and lower cortisol production, only a small percentage of women in this study were in relationships with men who had Stage 3 or 4 cancer. Thus, this finding could have been spurious. Ideally, this study would need to be conducted with large enough samples to examine systematic differences in psychological distress and HPA activity in PC partners whose mates differ based on medical characteristics. It remains unclear from the current study, which specific aspects of the cancer caregiving experience may have been considered traumatic to partners. For instance, we did not assess whether women were afraid that their partners were going to die, or whether they experienced distress related to their partners’ treatments, hospitalization, or helping them cope with the side effects of medical interventions. This information would help us to understand why partners of men with PC were more likely to report subthreshold posttraumatic stress symptoms, which would be useful in developing treatments tailored to meet the needs of this caregiver group.
The cortisol awakening response was below 50% among participants in this study, which is lower than what is typically seen in normal individuals (Wust et al., 2000
). Although the difference was non-significant, PC partners had a lower CAR than control participants (13% versus 39%). It is possible that non-compliance with the sampling schedule might explain the reduced CAR in PC partners. However, several studies have found lower CAR in individuals who suffer from PTSD (Chida and Steptoe, 2009
; Rohleder et al., 2004
; Wessa et al., 2006
). Thus, it is also possible that the lower CAR in PC partners was due to the presence of post-traumatic stress symptoms in this group.
Given the correlational nature of this study, we cannot infer that a causal relationship exists between partner PC diagnosis, PTSD symptomatology, and cortisol production. Low cortisol production may have preceded PC diagnosis and increased risk for PTSD. To determine causality, a longitudinal study would be necessary with data collection ranging from pre-diagnosis to post-treatment.
To our knowledge, this is the first study to examine diurnal cortisol patterns in spouses of men with cancer. Although these findings are preliminary and require replication, they suggest that the pattern of cortisol production in partners of men with PC may be associated with symptoms of PTSD resulting from the experience of caring for a spouse with cancer. The threat of losing a loved one to cancer is a traumatic experience that might lead to PTSD in some individuals. Although no published studies have examined the prevalence of PTSD in PC partners, female PC caregivers report clinically significant anxiety symptoms (Fletcher et al., 2008
) and are more likely to report PTSD symptoms (e.g., intrusive thoughts and avoidance) than PC patients (Eton et al., 2005
). These findings, in conjunction with our findings of lower cortisol production in spousal cancer caregivers, provide evidence that caring for a spouse/partner with PC may have adverse psychobiological effects. Additionally, these findings highlight the importance of developing interventions aimed at reducing risk of psychopathology in this group.