The psychosocial, endocrine and immune consequences of caring for a child with autism or ADHD
Introduction
To assess the psychophysiological consequences of chronic stress, the caregiver control model has focussed, in the main, on older caregivers of spouses with degenerative disease. Compared with age matched controls, elevated psychological distress and dysregulation of the endocrine and immune systems have been consistently demonstrated in older populations (Kiecolt-Glaser et al., 1996, Vedhara et al., 1999, Bauer et al., 2000, Gallagher-Thompson et al., 2006, von Kanel et al., 2006, Gallagher et al., 2009). For a more comprehensive review regarding the psychophysiological consequences of caregiver stress in older caregivers, refer to Lovell and Wetherell (2011). As a function of their advancing age, older caregivers experience endocrine and immune senescence, that is, a natural dysregulation of the endocrine system and down regulation of the cellular immune response (Bauer, 2005). To better model the link between caregiver stress and disease risk, researchers have begun to investigate the psychophysiological consequences of caregiver stress in parents of medically fragile children, that is, in populations not contending with age associated decline of the endocrine and immune systems (Miller et al., 2008, Gallagher et al., 2009, Rohleder et al., 2009). In the same way that older caregivers can expect the stress of caregiving to last an average, 3–15 years (Vitaliano et al., 2003), parents of medically fragile children can expect the economic and psychosocial demands of caregiving to extend into the late adulthood of the child (Kuster and Merkle, 2004).
Research that has assessed the psychophysiological consequences of caregiver stress in young and middle aged populations has been scarce and yielded inconsistent findings. The majority of research has focussed on caregivers of patients experiencing severe physical impairments such as, multiple sclerosis (that includes some cognitive and personality changes) and breast cancer (Vedhara et al., 2002, Cohen et al., 2002, Cohen and Pollack, 2005). Research has noted that antibody response to influenza vaccination could not differentiate young and middle aged caregivers of patients experiencing multiple sclerosis from age matched controls (Vedhara et al., 2002). From these findings, it might be concluded, therefore, that it is the interaction between caregiver stress and caregivers’ advancing age that dictates whether the stress of caregiving becomes an issue for immunity, that is, efficacy of the humoral immune response is preserved in young and middle aged caregivers not contending with immune senescence. More recently, however, research has demonstrated that, compared with parents of typically developing children, young and middle aged caregivers of children experiencing the same kinds of severe cognitive and behavioural impairments (i.e., Down's syndrome) that characterise older dementia patients demonstrated poorer antibody response to pneumococcal vaccination (Gallagher et al., 2009). Compared with other caregiver populations, depression and psychological burden are greater and, therefore, the experience of caregiving markedly more intense in caregivers of patients experiencing severe cognitive and behavioural impairments (Ergh et al., 2002, Vedhara et al., 2002, Pinquart and Sorensen, 2003). Rather than immune senescence, specific characteristics of the care recipient and concomitant variations in the intensity of the caregiving experience, therefore, seem to dictate whether the stress of caregiving becomes an issue for immunity (Gallagher et al., 2009).
The allostatic load model posits that stress responsive systems that mediate adaptive cardiovascular, metabolic and immunological changes in the face of fight/flight emergencies, can, if chronically activated, cause cumulative wear and tear on target cells in ways that foster increased risk for deleterious health outcomes (McEwen, 2003). Typically, basal HPA activity displays a robust diurnal pattern; levels of cortisol rise between waking and 30–45 min post waking (cortisol awakening response, CAR), decline across the day (diurnal cortisol slope) and reach a trough at around midnight (Smyth et al., 1997, Hucklebridge et al., 1998). As one index of allostatic load, disrupted patterns of cortisol secretion have been observed in young and middle aged caregivers of patients with acquired brain injury (Turner-Cobb et al., 2010). In support of the allostatic load model, the GC resistance hypothesis postulates that, as a function of persistent hypersecretion of cortisol, immune cells become functionally resistant to GC mediated signalling. Cortisol, therefore, is less able to effectively suppress proinflammatory transcriptional control pathways (Miller et al., 2002, Raison and Miller, 2003, Rohleder et al., 2009). Research has demonstrated how, as a function of GC resistance and concomitant disinhibition of the proinflammatory cascade, caregiver stress augments normal age related elevations in proinflammatory cytokines in older caregivers. In particular, findings from a six year longitudinal study revealed that, compared with age matched controls; concentrations of IL-6 were four times higher in older caregivers of dementia patients (Kiecolt-Glaser et al., 2003). Commensurate with these findings, elevated concentrations of IL-6 have been observed in other older caregiver populations (Lutgendorf et al., 1999, von Kanel et al., 2006). Cortisol hypersecretion, reduced immune system GC sensitivity and elevated concentrations of the systemic proinflammatory biomarkers, IL-1 and CRP have also been observed in young and middle aged caregivers of children with aggressive brain cancer (Miller et al., 2008, Rohleder et al., 2009). Relative to age matched controls, caregivers might, therefore, be at greater risk for conditions sensitive to disinhibition of the inflammatory response, including cardiovascular disease, type II diabetes and disorders of the musculoskeletal system (Pradhan et al., 2001, Ridker et al., 2003, Tak et al., 2009). Moreover, proinflammatory cytokines signal the brain to induce non specific symptoms of sickness such as malaise, nausea, headache, listlessness, fatigue, and hyperalgesia (Dantzer, 2001) via vagal nerves or leaky regions of the blood brain barrier (Dantzer et al., 2008).
Young and middle aged caregivers of patients with traumatic brain injury report feeling isolated from social support networks (Marsh et al., 1998); moreover, an inverse relationship between chronicity of caregiving and availability of social support has been demonstrated (Kiecolt-Glaser et al., 1991). Elevated psychological morbidity and reduced sensitivity of the immune system to the immunosuppressive effects of cortisol has been demonstrated in young and middle aged caregivers that reported diminished availability of social support (Ergh et al., 2002, Miller et al., 2002). It, therefore, becomes increasingly relevant to assess social support, in order that we learn more about how the availability of family and friends might mediate changes in disease trajectories.
This study is the first to assess the psychosocial, endocrine and immune consequences of caregiver stress in a cross sectional sample of young and middle aged caregivers of children experiencing autism and attention deficit hyperactivity disorder (ADHD) compared against parents of typically developing children. On the basis of past work, we expected that caregivers would report greater psychological distress, diminished availability of social support and more frequent episodes of physical ill health. We also expected that caregivers would display disrupted patterns of cortisol secretion and elevated systemic concentrations of proinflammatory biomarkers. On the basis of previous work, we assessed variations in cortisol patterns and social support as potential mediators of these effects.
Section snippets
Parents
Parents (n = 56) of children with autism and ADHD were recruited from support groups, schools and charities. Parents of typically developing children (n = 22) were sought from an under/postgraduate and staff population. Caregivers were recruited according to the following criteria: aged 20–60 years, providing care for at least one child (aged 3–21 years) with autism or ADHD and living at home full time, not providing care for another individual with chronic illness, not pregnant/breast
Preliminary analyses
Table 1 presents means, standard deviations and range for demographic, behavioural and biomedical characteristics in caregivers and controls. Groups were statistically indistinguishable with respect, gender, height, weight, BMI, marital status, number of children in the household, annual income, alcohol consumption, nicotine intake, frequency of exercise, use of oral contraceptives, phase of the menstrual cycle, time of waking and quality of sleep (all ps > 0.09). Results did, however, reveal
Discussion
Caregivers scored markedly higher on all measures of psychological distress; however, patterns of cortisol secretion did not differentiate the groups. That is, both caregivers and parent controls demonstrated the prototypical pattern of cortisol output across the day. These data are commensurate with recent findings in other young and middle aged caregivers that have demonstrated increased psychological distress, but failed to observe disparities in cortisol secretion patterns (Miller et al.,
Role of funding source
The research was funded by the School of Life Sciences, Northumbria University, UK. The school had no role in study design, collection and analysis of data, writing of the manuscript or, the decision to submit the manuscript for publication.
Conflict of interest
All authors declare that there are no conflicts of interest.
Acknowledgement
The authors would like to thank Anthea Wilde for conducting cortisol and immune assays.
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