Study eligible patients with diabetes were aged ≥18 years and endorsed one of two cardinal depression symptoms more than half the days to nearly every day and scored ≥10 on the PHQ-9, indicating a high likelihood of clinically significant depression. Exclusion criteria were acute suicidal ideation, a score of ≥8 on the Alcohol Use Disorders Identification Test alcohol assessment, recent lithium/antipsychotic medication use, and inability to speak English or Spanish. Of 1,803 diabetic patients, 1,729 (95.8%) were screened (1,255 [72.6%] female); 30% met depression criteria (female 32.8% vs. male 23.4%, P < 0.001). Excluding patients meeting alcoholism criteria, acute suicidality, or other psychiatric condition, enrollment was 80.5% female and 71.1% male (P = 0.04). Of 387 (78.7%) enrolled patients (15 were non-Hispanic), 193 were randomized to the INT group and 194 to the EUC group ().
Baseline demographic, clinical, and functional characteristics are summarized in and . Patients were predominantly Latina, foreign born, in the U.S. ≥10 years, unemployed, and had not completed high school. Nearly 98% of patients had type 2 diabetes (eight had type 1 diabetes). Mean A1C levels were 9.05% in the EUC group and 9.01% in the INT group; 80% in the EUC group and 86% in the INT group had one or more diabetes complications. Over 60% had BMIs ≥30 kg/m2 and 83% had one or more comorbid medical conditions. Over 50% of patients had moderate to severe depression (PHQ-9 ≥15); nearly 19% reported a history of depression. Patients from the two study clinics varied significantly with respect to birth place, language use, diabetes treatment, mean A1C levels, self-care management, comorbid medical illness, socioeconomic stress, and depression score.
Receipt of depression care and clinical, functional, and socioeconomic outcomes
Over the 12-month intervention, 169 (87.6%) patients completed an initial visit with a DDCS and 162 (83.9%) continued intervention treatment. A total of 104 (53.9%) received both PST and antidepressant medications, and 49 (25.4%) received only PST and 9 (4.7%) received only antidepressant medications. PST participants had a mean (± SD) of 8.7 ± 5.4 sessions. Of 113 INT patients receiving antidepressant medication, 103 patients remained on medication for a mean of 8.8 months over the 12-month intervention, whereas 10 (8.8%) patients discontinued antidepressant medication after 30 days or less. Estimated per-patient intervention costs totaled $820.
Receipt of depression care
INT patients predominantly chose PST first-line treatment. INT versus EUC patients were significantly more likely to receive antidepressant medication and/or counseling/psychotherapy (PST in the INT group) at 12 (all P values <0.001) and 18 (P values 0.01 to <0.001) months (). Over 12 months, 83.9% of INT patients received depression treatment (49 PST, 9 antidepressant medication, 104 both) versus 32.5% of EUC patients (37 antidepressant medication, 11 self-reported counseling, 15 both). Of patients prescribed antidepressant medication, over 12 months, a dosage increment or change in type of medication was provided to 63 (55.8%) INT versus 10 (19.2%) EUC patients. Thirty-five INT patients attended one or more PST support group sessions. Patient satisfaction with emotional care assessed at the 18-month blinded survey found that INT patients reported significantly greater satisfaction (satisfied to very satisfied) compared with EUC patients (89.5 vs. 77.9%; odds ratio 2.43 [95% CI 1.23–4.77]; P = 0.01).
At 6, 12, and 18 months, INT patients were significantly more likely to have a ≥50% reduction in SCL-20 baseline score (57, 62, and 62%) versus EUC patients (36, 42, and 44%) (adjusted odds ratio range 2.46–2.57; P < 0.001) (). Significant group difference in a ≥50% decrease in PHQ-9 score also was found at each follow-up. Intervention patients had significantly greater odds of depression remission based on SCL-20 <0.5 at 6 and 18 months, with similar trends at 12 months as well as remission at 6 and 12 months based on PHQ-9 <5. Significantly fewer INT than EUC patients had persistent major depression (i.e., PHQ-9 ≥10) at each follow-up. There were no significant interaction effects on depression improvement or remission between study groups and baseline depression severity, sex, language, time in the U.S., education, use of insulin, time with diabetes, glycemic control, or obesity (BMI ≥30 kg/m2) at each follow-up. Significant interactions were observed between study site and study group only for depression remission at 6 months (P = 0.03 for interaction; adjusted odds ratio 4.12 [95% CI 1.81–9.42] for El Monte and 1.28 [0.66–2.49] for Roybal clinic) and between age and study group only for depression improvement at 18 months (P = 0.01 for interaction; 0.87 [0.33–2.27] for patients aged <50 years and 3.80 [2.05–7.02] for patients aged ≥50 years). Analyses were repeated with the Hispanic-only and type 2 diabetic patient samples and the results were identical.
Clinical, functional, and socioeconomic outcomes
There were significant study group–by–time interactions over 18 months in mean diabetes symptoms, SF-12 emotional and physical functioning and pain, Sheehan disability, financial situation, and number of social stressors (). Comparisons of adjusted mean scores between study groups at 6 months found that INT patients had significantly better emotional functioning and less functional impairment, pain impact, diabetes symptoms, and likelihood of worsening financial situation; significant improvement in financial situation continued at 12 months; and significantly improved Mental Component Summary-12 was still present at 12 and 18 months. No group differences were found in A1C, diabetes complications, mean self-care management scores, or BMI over time or at each follow-up. Again, there were no significant differences in results for Hispanic- or type 2 diabetes–only samples.
To our knowledge, this is the first randomized controlled trial of collaborative care for predominantly Hispanic patients with diabetes in public safety-net clinics. Findings suggest that a collaborative care model, socioculturally adapted for low-income patients, resulted in significant reductions in depressive symptoms, improvements in emotional and physical functional outcomes, and lower burden of diabetes symptoms and pain compared with enhanced usual care. The importance of study findings is underscored in view of data that Hispanics in the U.S. have the highest estimated lifetime risk for diabetes (males 45.4% and females 52.5%) (22
In light of known racial/ethnic disparities in receipt of depression care, it is noteworthy that INT patients had significantly higher rates of participation in PST, the length of time in which patients adhered to antidepressant medications, and the degree of satisfaction with the quality of depression care. Providing culturally sensitive acute and maintenance care that includes facilitating access to socioeconomic resources and is organizationally integrated within safety-net care systems is likely to have a marked effect on decreasing disparities in depression care among low-income and Hispanic patients with diabetes.
Despite the improvement associated with the intervention in quality and outcomes of depression care as well as improvements in functioning and decreased diabetes and pain symptom burden, no intervention effect on A1C or self-care management was found. An association between poorer glycemic control and depression has been frequently reported; however, results of treating depression and improving glycemic control are mixed. The trials reporting a change in A1C with improvement of depression were with less representative populations and often compared an evidence-based depression psychotherapy and diabetes education to diabetes education alone (23
). There is evidence that Hispanics report self-monitoring of blood glucose as being very difficult (24
), while in this study, patients often expressed to the depression care manager that general management of diabetes was socially and economically stressful.
Improving depression symptoms in patients with diabetes in prior collaborative care studies has been shown to be associated in comparisons with usual primary care with a high probability of achieving savings in total ambulatory medical costs (8
). The higher costs associated with providing enhanced mental health care were offset by greater savings in medical costs (8
). Black et al. (25
) found in a large longitudinal study of an aging Hispanic population in the southwestern U.S. that depression markedly increases the risk in patients with diabetes of macro- and microvascular complications, incident physical disability, and mortality. Therefore, further studies are needed to ascertain whether improving outcomes of depression in patients with diabetes could decrease disability, complications, mortality, and medical costs.
Study results are encouraging and are consistent with other recent studies that have found that depression care management improvement strategies are effective over time among low-income and ethnic minority populations (12
). Improving treatment of depression by integrating a depression specialist (supervised by a psychiatrist) into primary care along with long-term follow-up may be especially helpful in view of the challenges faced by physicians in community safety-net clinics. Ensuring that linguistic, cultural, and economic factors are incorporated with collaborative care management that includes mental health personnel is also likely to reduce disparities in acceptance and receipt of treatment. Of 17 clinic physicians, clinic medical directors, and nursing staff interviewed, all reported satisfaction with the intervention model, and the sustainability of the model is under active consideration. Our culturally focused recruitment and follow-up outreach efforts are likely to have reduced potential attrition rates that did not vary between study groups and resulted in better-than-usual geographic mobility of the study population in these safety net clinics.
Not unique to health services effectiveness trials, our study design may have biased our comparisons in favor of the EUC group. Increased prescription of antidepressant medications over baseline among usual care patients may be attributable in part to the following enhanced usual care design: all patients were screened and clinic physicians were notified of patients meeting study criteria, all physicians participated in the depression care didactic sessions and were given a copy of the stepped-care algorithm, and acutely suicidal patients were referred for further clinical evaluation and treatment. Because the same practitioners treated both intervention and EUC patients, there may have also been a spillover effect on quality of depression treatment. EUC patients may have also benefited from having received the linguistically and idiomatically adapted patient and family educational pamphlets and the information provided on available supportive services. These biases may contribute to an underestimation of the effectiveness of the intervention compared with usual care outside a research trial. Additional limitations include our reliance on self-reports of chronic medical conditions and potentially underreporting of use of antidepressants and psychotherapy.