In a population cohort with symptomatic hip and knee OA, we examined the relationship between depressed mood, evaluated using the SF-36 MH score, and mental health-related health care use. Controlling for potential confounders, worsening MH scores were significantly and independently predictive of a greater likelihood of receiving mental health services. However, consistent with previous studies in other clinical populations[17
], and despite mounting evidence of a strong association between chronic pain conditions, like arthritis, and depression[8
], substantial care gaps remained. Fewer than half with depressed mood, as we defined it, experienced one or more mental health-related physician visit to a PCP or psychiatrist; among those aged 65+ years, who were eligible for drug benefits coverage, the proportion receiving any care (physician visit and/or prescription for an anti-depressant) was only modestly higher at 56.7%.
Among our participants, more than one-quarter (29%) had MH scores below our cut-point, indicating probable depression. Probable depression was more common among those who were younger, resided in the urban region, had lower income and education, greater OA severity and greater comorbidity. These findings are consistent with those of others. A cross-sectional analysis of the 2002 US National Health Interview Survey[33
] found that 26.2% with physician-diagnosed arthritis reported frequent anxiety or depression in the previous 12 months; 5.6% met criteria for 'serious psychological distress', which was significantly and independently associated with younger age, lower socioeconomic status, divorce/separated marital status, greater pain and functional limitations, and comorbidity. A smaller UK study found that 40.7% of 54 participants with lower limb OA[34
] met criteria for clinically significant anxiety or depression, with worse scores significantly related to greater OA pain.
Depressed mood in the setting of chronic pain has been linked with greater pain intensity, anxiety[35
], sleep disturbances, decreased energy, decline in cognitive function and poor medication adherence[36
], each of which may increase health care use. In the current study, depressed mood predicted a greater number of visits to both PCPs and psychiatrists and a greater likelihood of receiving an anti-depressant prescription. Katon et al. [37
] similarly found that, among primary care patients aged 60+ years, and controlling for age, sex, and comorbidity, inpatient and outpatient health care utilization, including PCP and specialty medical visits and prescriptions for anti-depressants, were higher among those who did versus did not screen positive for clinical depression on a structured clinical interview. However, consistent with our findings, only 45% of the individuals with depression experienced any mental health care.
Although women were not more likely than men to be classified as having probable depression, women were more likely to receive mental health care. A similar relationship has been shown by others[19
] and may be related to a greater propensity to seek treatment for mental health problems among women than men[38
Among those 65 and older at baseline, the probability of receiving mental health care decreased
with increasing age. One potential explanation is that the greater comorbidity that accompanies increasing age is perceived as precluding the safe use of anti-depressant therapies. However, among our study participants, while the number of reported comorbid conditions did increase with increasing age, age was a significant predictor of the probability of receiving mental health care and remained significant even after controlling for the number of comorbid conditions, suggesting that the effect of age was not simply as a proxy for greater comorbidity. Other potential explanations include under-recognition of depression among older adults, possibly resulting from differences in the clinical presentation of depression by age, and/or a higher threshold for seeking mental health care among older individuals[39
]. Further, self-reported general health status modified the relationship between MH scores and likelihood of receiving mental health care. Among those with relatively good general health status, worsening mental health was associated with an increased likelihood of receiving mental health care, but as general health status declined, this effect was attenuated. One explanation for this finding is that, in the setting of multiple medical conditions, for which poor self-reported general health status may be a proxy, the management of some conditions may be neglected if others consume attention[41
]. Alternatively, these individuals may have their mental health care needs addressed within the context of physician visits coded for their other health care problems. Further research is warranted to disentangle the influences of general health and mental health status on provision of mental health care.
Among those who received at least one mental health-related physician visit, the number of visits experienced was significantly greater in urban residents and those with more education. It has previously been shown that urban residence is associated with greater use of mental health specialist services[42
], likely related to greater access to these services. The association with higher socioeconomic status is concerning in light of the documented higher risk for depression among older adults with lower socioeconomic status[33
]. This finding may reflect differences by socioeconomic status in perceptions of need, health-seeking behaviours, likelihood of receiving treatment from a physician, and adherence to recommended therapies once prescribed. Additional research is warranted to determine if inequities in care provision exist.
Taken together, our findings suggest under-treatment of depressed mood among older adults with painful OA. Identified barriers to the diagnosis and treatment of depression in the primary care setting, where most mental health care was received by our participants, include: barriers to help-seeking for mental health issues due to the stigma attached to these conditions[38
] and the perception that a depressive state is a normal part of aging[44
]; physicians' attitudes, knowledge and skills with respect to mental health diagnosis and management[17
]; the complexity of depression management in the elderly[17
]; and difficulty discriminating the clinical symptoms of OA from those of depression[39
]. Strategies are needed to address these barriers as effective therapies exist [47
] since, in the setting of painful OA, improved treatment of depression may reduce not only depressive symptoms, but also arthritis pain, activity limitations, and overall quality of life[16
This was a retrospective cohort study in which we utilized previously completed questionnaires, which incorporated the SF-36. As such, we did not have access to the medical records of the participants, nor would we be able to retrospectively evaluate whether or not the participants we categorized as having 'probable depression' met DSM-IV criteria for clinical depression at that time. For this reason, we have been careful to use the term 'depressed mood' as opposed to 'clinical depression' to describe these individuals. However, despite this limitation, we would argue that individuals who have sufficient symptoms of depression to meet our criteria for 'probable depression' would warrant a closer look by the family doctor and/or a referral to a specialist, even if a psychiatrist decided that the patient did not meet the DSM-IV definition. Study strengths include the large sample recruited from the community and use of linked survey and administrative data. However, there are also potential study limitations. First, we defined depressed mood using a validated cut-point on the SF-36 MH subscale, shown to have 78.7% sensitivity and 72.1% specificity for clinical depression based on clinical interview using the MINI-MDE module[49
]. Thus, there remains the potential for misclassification of depressed mood in our cohort. Second, the validated algorithm used to identify mental health-related PCP visits using administrative data has high specificity, but only 80% sensitivity [26
]. Thus, we may have underestimated mental health-related PCP visits, and thus overestimated the depression-care gap. Third, since Ontario drug benefits are restricted to individuals aged 65 years and older, we were only able to examine use of medications for depression among those aged 65+ years at baseline. However, this subgroup represented over 70% of our total sample. Fourth, for almost one-third of anti-depressant prescriptions identified in this cohort subgroup (30.4%), the 'days supplied' variable was missing; thus, we relied on the filling of a prescription as a proxy for the participant taking the medication. Finally, we made the assumption that anti-depressants were prescribed for the management of depressed mood; some may have been prescribed instead for the management of chronic arthritis pain and/or associated fibromyalgia. Both these decisions may have resulted in over-estimation of receipt of mental health care.