This cross-sectional study is one of the largest studies conducted to date analyzing the predictors of depression in caregivers of patients with moderate to severe dementia. We confirmed previous research documenting very high rates of depression in caregivers.18
Nearly one-third (32%) of caregivers had 6 or more symptoms of depression on the GDS-15, a score that in clinical settings is suggestive of the diagnosis of major depression32
and strongly associated with adverse outcomes such as functional decline, hip fracture, and nursing home placement.20,21,35
Our study demonstrates that caregiver depression is a complex process, mediated by cultural factors (as measured by the ethnicity of the patient), patient characteristics, and caregiver characteristics. Patient characteristics that predicted caregiver depression included younger patient age and dementia severity. In terms of dementia severity, multiple dimensions of severity are important including ADL function and behavioral symptoms. Caregiver characteristics that predicted depression included low levels of financial resources (income), the relationship to the patient (daughter or wife), more hours spent caregiving, and poor caregiver functional status. While most of these factors have been demonstrated to be predictors of caregiver depression in other studies, this study is one of the few to have examined all of these factors simultaneously.13,18,22
By demonstrating that all of these factors must be considered to understand caregiver depression, our results demonstrate that caregiver depression can only be understood by a complete understanding of both the patient and caregiver, and their cultural context.
Our results demonstrate important ethnic differences in rates of caregiver depression, with the lowest rates in caregivers of black patients, and the highest rate in caregivers of Hispanic patients. These results are consistent with most, but not all prior studies.13
The lower rate of depression in caregivers of African-American patients may be explained by other research demonstrating that African-American caregivers respond differently to the stresses of caregiving than white caregivers.13,36
The markedly higher rate of depression in caregivers of Hispanic patients is consistent with earlier studies showing higher rates of depression and/or personal role strain among Hispanic caregivers.11,37
Possible explanations may also be found in other research. Baseline levels of depression vary among ethnic groups, and some studies have indicated that Hispanic elders have a higher prevalence of depression,38
though it is not clear whether this reflects true differences in symptomatology or differential item functioning of the instruments used to measure depression. The meaning attached to dementia and its disruptive effect on the family unit may have particular significance for Hispanic caregivers.38–41
Different levels of acculturation of Hispanic caregivers relative to the patient for whom they are caring may also impact caregiver depression rates.39
Ethnic differences in caregiver depression may also be influenced by different expectations about responsibilities toward elders, competing demands on time that may vary by culture and ethnicity, and differential local availability of other caregivers.
Interestingly, the relation between ethnicity and depression is different from the relationship between ethnicity and risk of nursing home placement we previously reported in these patients.24
While caregivers of Hispanic patients have considerably higher rates of depression than caregivers of white and black patients, they have considerably lower rates of nursing home placement. This discordance between rates of caregiver depression and nursing home placement needs evaluation in future studies.
Behavioral disturbances (particularly angry or aggressive behavior) and decreased patient ADL function both were independently associated with caregiver depression. Our findings with respect to behavioral disturbances are consistent with prior studies.18,22
However, most studies have not identified a relationship between patient ADL function and caregiver depression. Since patient ADL function is strongly correlated with other predictors of caregiver depression, such as caregiver work hours and behavioral disturbance, smaller studies may not have been able to identify the moderate but clinically important impact of patient ADL function.
Our findings with respect to caregiver characteristics further demonstrate that caregiver depression is a complex interplay of medical, social, and economic factors. Both male and female spouses had high levels of depression, but among adult children, levels of depression were higher among daughters than sons. Both the health (as measured by ADL and IADL function) and economic resources (as measured by income) caregivers bring to caregiving predicted the risk of depression. Physical and economic health probably both mitigate the stresses of caregiving. Caregivers with better ADL function are probably more able to withstand the physical demands of caregiving. Caregivers with higher income probably have more access to supportive services like home health aides and adult day health that may help minimize the burdens of caregiving.
Our study has several strengths. The sample size is large, making this one of the largest studies of caregiver depression. We considered a diverse array of social, patient, and caregiver characteristics that could plausibly influence depression, and our large sample size made it likely that we could identify clinically important effects. However, our study also has some limitations. First, the generalizability of our findings is uncertain because we studied patients with fairly advanced dementia who agreed to be part of an intervention. However, this impact on generalizability is balanced by the 8-site design of our study, making our patient population more diverse than most prior studies. Second, we relied on physician diagnoses of dementia, rather than clinical evaluations of patients. Third, while we considered multiple predictors of caregiver depression, we did not have information on other predictors such as the quality of the caregiver–patient relationship or caregivers’ stress appraisals.22,42
Fourth, our measure of depression was the GDS and not a DSM-IV diagnosis of depression. While scores of 6 or more on the GDS are strongly correlated with clinical diagnoses of major depression, not all patients with scores at this level would meet diagnostic criteria for major depression.31,32
However, in older patients, depressive symptoms adversely impact quality of life, regardless of whether or not a patient meets criteria for major depression. Furthermore, high GDS scores are correlated with poor outcomes such as functional decline and death, regardless of whether or not the patient has major depression.20,21
Fifth, we only interviewed 1 caregiver per patient. In many cases, patients may have more than 1 caregiver, and dynamics between the caregivers may have impacts on caregiver depression. Sixth, we did not directly measure caregiver ethnicity. In some cases, the race of the caregiver and patient probably differed. Finally, many of our predictor variables were based on caregiver reports and it is possible these reports may have been influenced by depression. For example, depressed caregivers may be more likely to overestimate the physical limitations of the patient and the extent to which patient behaviors are considered problematic and underestimate the quality of life of the patient.43
This, and the cross-sectional nature of the study, makes it difficult to differentiate whether some variables influence caregiver depression versus whether caregiver depression influences the reporting of these variables. A similar issue arises with respect to the reporting of hours spent caregiving. Many caregivers reported spending close to every hour of the week caring for the patient. It is possible that depressed caregivers may have only felt they were spending more time providing care. However, these reports may realistically reflect the predicament many caregivers face in which they can never leave the patient alone and may need to provide care at any hour. For example, many symptoms of dementia, including wandering, day–night reversal, agitation, and incontinence frequently interrupt the sleep of caregivers.44
The most important finding of our multivariable analysis is that multiple caregiver and patient processes independently predict caregiver depression. This demonstrates that caregiver depression is a problem that needs to be viewed from a wide clinical and social framework. However, it would not be correct to make excessive causal inferences based on the final variables that did or did not remain in our multivariable models. There are multiple reasons potentially important determinants of an outcome may not remain in a multivariate model. This includes control for a variable more distal on the causal path, or inclusion of a collinear variable. For example, for spouses, caregiver and patient age may be closely correlated, and the selection between these 2 variables may be influenced by chance.
Because of the high prevalence of caregiver depression, and its potential association with adverse outcomes, clinicians should have a high index of suspicion for depression in their patients who care for family members with dementia.5–21
While little research has focused specifically on the treatment of depression associated with caregiving, it seems likely that pharmacologic and nonpharmacologic treatments that are effective in general groups of people with depression should also be effective in caregivers with depression. Furthermore, some evidence suggests that interventions focused on caregiver support may reduce rates of caregiver depression and burden, as well as rates of nursing home placement.45
In conclusion, we found that caregiver depression is a complex clinical and social problem, influenced in part by the ethnicity of the patient, as well as multiple patient and caregiver characteristics. Like other common problems related to aging, caregiver depression is therefore best approached by viewing it as a problem induced by the interactive effects of multiple risk factors, rather than a problem induced by any single dominant risk factor. This suggests that efforts to identify and treat caregiver depression will need to be multidisciplinary, consider the cultural context of the patient and caregiver, and focus on multiple risk factors simultaneously.
Supported in part by an independent investigator award (K02HS00006-01) from the Agency for Healthcare Research and Quality and the Paul Beeson Faculty Scholars Program.