Background and rationale
According to the Global Health Estimates by the World Health Organization (WHO), non-communicable diseases, such as cardiovascular diseases and diabetes, accounted for 68.4% of total deaths worldwide in 2015 [
1]. Up to date global burden of disease data also reveals that depressive disorders are the single largest cause of global disability, leading to considerable losses in health and functioning and contributing to nearly 800,000 deaths by suicide per year [
2,
3]. Population ageing means that cardiovascular diseases and diabetes are becoming more prevalent, while depression might further limit the capacities of this ever increasing older workforce [
3,
4]. Moreover, studies have revealed that depression comorbid with medical conditions is the rule rather than the exception, as up to two thirds of the depressed subjects were diagnosed with physical health comorbidities in a Scottish country-wide primary care study [
5], with the disease cluster of cardio-metabolic conditions and depression being one of the most common multimorbidity patterns throughout clinical settings according to a systematic review [
6]. Comorbid depression has been associated with incremental decrements in health [
7], prolonged hospital stays and higher chance of rehospitalization [
8], lower treatment adherence [
9], and increased risk of mortality [
10,
11]. Thus, endorsement of the statement “no health without mental health” should readily translate into evidence-based clinical practice guidelines that consider physical and mental health comorbidities [
12].
During the past decades, the Collaborative Care Model (CCM) has proven successful in integrating behavioral health services into primary care [
13]. Under this model of care, mental health care is provided in a coordinated fashion with the support of a case manager, supervision by a consultant psychiatrist, and the use of patient-reported outcome measures to tailor clinical decision-making to patients’ needs [
13]. Studies have consistently reported that the CCM improves depressive symptoms, health-related quality of life, and social functioning of depressed individuals, with no net increase in health care costs [
14]. CCM is effective in the treatment of people with depression alone or with comorbid medical conditions [
15]; and it might be beneficial for glycemic and blood pressure control in depressed patients with poorly controlled chronic diseases [
16]. Additionally, the current literature on CCM has identified some essential components for the implementation of effective integrated disease management programs, such as the inclusion of cognitive-behavioral therapy and problem-solving techniques [
17], or motivational interviewing interventions [
18], self-help resources delivered through the Internet or computer-based applications [
19‐
21], timely case manager follow-up within the first 4 weeks to increase clinical attention and patient engagement [
22], and psychiatric consultation for those patients not achieving improvement after 2 months [
22]. However, evidence and experts’ recommendations for effective CCM usage come mainly from developed countries [
14], and may not wholly apply to developing nations.
Chile is a developing, high-income Latin American country that has made major advances over the last 30 years in the management of medical and mental health conditions. For instance, Chilean governments have made a strong commitment to promote healthy living and prevent chronic diseases through community-based health programs for people covered by public health insurance [
23], and have developed a comprehensive community-based mental health care network, integrating mental health into primary care throughout the country [
24]. Moreover, based on the success of a randomized controlled trial to treat depression in low-income women in primary care clinics in Chile’s capital city, Santiago [
25], a stepped-care program for depression management, which combined medical and psychosocial interventions, was implemented in 2001 and rapidly scaled-up across primary care facilities in the country [
24]. Complementarily, the Chilean Regime of Explicit Health Guarantees, a comprehensive health reform enacted in 2005, mandated guarantees of access, quality, opportunity, and financial coverage by public and private health insurance for priority diseases and conditions [
24]. Hypertension, type II diabetes, and depressive disorders were part of the first set of 56 priority diseases, ensuring access to an extensive, evidence-based basket of benefits which are structured according to clinical practice guidelines, informing quality, cost-effective primary care practice.
Despite substantial progress towards universal health access and coverage in Chile [
26], especially for depression [
24], effective coverage for hypertension and diabetes remains particularly low compared to infectious diseases or maternal and child care [
26]. Furthermore, according to the Chilean National Health Survey 2016–2017, there has been a sustained increase in the proportion of people with diabetes [
27], while no variation has been observed for the population prevalence of depression [
28]. These figures may be attributable to the minimum impact of preventive interventions, as evidenced by the prevalence of cardiovascular risk factors [
26], or to important inconsistencies in the provision of treatment, as in the case of depression, where diagnostic inaccuracy and treatment dropout are the main problems in the management of depressed primary care patients [
29,
30]. Moreover, while 80% percent of depressed patients at primary care clinics had comorbidity [
31], and depressive symptoms are common among hypertensive patients [
32], the Chilean clinical practice guidelines for cardio-metabolic and depressive disorders do not consider their common comorbidity in primary care settings. Thus, the country’s epidemiological and health services profile, characterized by a tendency towards ageing, highly prevalent non-communicable diseases, and mental disorders, motivates the urgent search for effective primary care interventions integrating a mental health component in the management of chronic diseases.