Strengths and limitations
The diagnoses in this study were made in the context of actual patient needs and in the context of the delivered care. The long-term registration database that was used, has maintained a consistent classification system in a stable population.21 This population is representative for the general Dutch population.22,23 A comparison of the study sample with the mortality data of the general Dutch population in 1990 showed that the study sample is representative concerning the proportion of causes of death (cardiovascular disease, COPD, and cancer) as well as the proportion of male and female deaths within the different causes of death.29 Furthermore, the classification system has been proved to adequately diagnose depressive disorder.16
This study has several limitations. To improve the consistency of this study population and the consistency of the patient–doctor relationship, patients who were listed in the practice <5 years were excluded. This could have resulted in excluding patients with an unstable life, patients who left the practice out of dissatisfaction with their doctor, or patients who were admitted to a nursing home in the last phase of their life. Patients with major life events such as moving house may be at a greater risk of developing a depressive disorder. However, in general the CMR registration has a stable practice population. Furthermore, if a problem arises in the patient–doctor relationship that results in the ending of this relationship, it is possible for patients to stay in the same practice with a different GP and thus still be part of the CMR database. This makes it unlikely that the results have been severely influenced by this bias.
Furthermore, the inclusion of different diagnoses in the causes of death groups can be somewhat arbitrary, especially in the case of death by COPD or cardiovascular disease, because some of the diagnoses, such as pulmonary embolus, can be linked with both COPD and cardiovascular disease. It is unlikely that this has influenced the results because of the very low prevalence of pulmonary embolus.
Regarding the diagnostic process, first, it is not known how individual patients in this sample were assessed for depressive disorder by their GP. Secondly, because different physicians were participating in the CMR there could have been inter-doctor variation in assessing depressive disorder. In general, this is assumed to be small because criteria for diagnosis are discussed in monthly meetings, where the application of diagnostic criteria is monitored. However, GPs may have different views or different ways of assessing depressive disorder in the last phase of life15 that has not been monitored specifically. Furthermore, in interpreting the findings of this study, it must be considered that depressive disorder throughout the 20 years of data that were included in this study may not have been a stable concept. Changes in perspective on depressive disorder, for example the concern for medicalisation and overtreatment,30 may influence the assessment of depressive disorder by physicians. In this study, it is unclear what perspective on depressive disorder the GPs used over the years.
This study was too small to compare differences in the incidence of depression in the different diagnosis groups. It is likely that people who suffer from COPD, cardiovascular disease and cancer experience different disease trajectories and it could be that also the incidences of depressive disorder are different for the different disease trajectories.20 Moreover, different cancer types are known to specifically increase the risk for depressive disorder, possibly because of the cause of specific biological characteristics of depressive disorder.31–33 Furthermore, this study aimed to explore the incidence of depressive disorder in the last phase of life. However, the patients included in this study suffered from a mix of chronic and subacute causes of death. It is possible that there are differences in incidence of depressive disorder between these groups.
This study did not explore other psychiatric comorbidity, such as anxiety disorders, that can be related to mood symptoms and may also have a high incidence in palliative care patients. In a previous study a prevalence of anxiety disorders of 7.6% is reported in advanced cancer patients.34
This study reported new episodes of depressive disorder in the last year of life. Patients who were already diagnosed with depressive disorder before their last year of life and continued to suffer from depression in their last year of life, were not included in the reported last-year-incidence.
Comparison with existing literature
Two reviews on depressive disorder in palliative care patients conclude that depressive disorder is common and there are concerns about underdiagnosis and undertreatment.1,5 However, the conclusion of the first review was that the quality of the evidence was poor and that the samples of patients were generally small.5 Although the second review has been based on a literature search, no details were provided of the review methodology and the influence of study quality on the outcomes. So, although the findings of these reviews contrast with the findings of the current study, the low incidence of depressive disorder in the last year of life is considered a valid result from reliable, real life data. The low incidence is in the range of the 1-year-incidence in the general population.
A possible explanation for the relatively low incidence of depressive disorder in this study may have been that the diagnoses in this study were made in the context of delivered care, guided by the patient’s agenda and in the context of patients’ needs in contrast to population research where depression is diagnosed with questionnaires or psychiatric interviews. Possibly GPs do not easily classify depressive symptoms in a palliative care context as depressive disorder as they consider these, in accordance with the patients, as normal reactions in the context of the end of life. Indeed, a recent focus group study showed that while GPs are sometimes reluctant to classify sadness as depression in a palliative care context, they frequently attend to normal sadness in palliative care patients.15 GPs can attend to emotional issues in a palliative care context without dichotomising the complex pattern of complaints into normal or disorder and with a explicit focus on the context of the depressive complaints that the patient experiences.
Implications for practice and research
Previous studies in palliative care patients with cancer report high numbers of depressed patients.1,2,4 Based on the findings of this study, the assumption that the last phase of life is a risk for depression may be incorrect. The question remains whether depressive disorder is truly not as common in patients in the last phase of life than has been previously assumed, or whether this is caused by methodological issues such as method of registration and the context of the assessment.
Finally, if the incidence of depressive disorder is low, it does not mean that there is no patient need for care for mood symptoms in the last phase of life. Patients may benefit from a broader classification of emotional issues, in which support can be provided without dichotomising complaints of sadness into normal or depressive disorder. It is recommended that the context of the patient is explicitly included in this process of diagnosis and suggest that patient burden and patient need for support for emotional issues should be included in the assessment.
This seems congruent with the way GPs manage mood symptoms of their palliative care patients; they seem to manage these symptoms with a strong focus on the context of the patient without needing a diagnosis of a disorder.15 Therefore, it is recommended studying the last phase of life with a broader concept of depression to gain more insight in the actual situation in clinical practice.