Abstract
Introduction. Liaison Psychiatry is a key subspecialty in the comprehensive management of hospitalized patients in general hospitals. Its implementation at the Centro Médico Nacional 20 de Noviembre has enabled the approach to medical-psychiatric comorbidity within a biopsychosocial framework.
Objective. To describe the development, current structure, and outcomes of the Liaison Psychiatry Service at the CMN 20 de Noviembre.
Methods. Descriptive retrospective study based on institutional documentation and service statistics from recent years.
Results. The article presents the historical background of the service, the current care model, and the most frequent diagnoses handled through consultations. The clinical, academic, and organizational benefits of integrating mental health in a tertiary care hospital are highlighted.
Conclusions. The experience of CMN 20 de Noviembre confirms the importance of Liaison Psychiatry in providing comprehensive patient care, strengthening the doctor-patient relationship, and optimizing hospital resources.
Key words: Tertiary Care Hospital, Liaison Psychiatry, Mental Health Integration
Introduction
Liaison psychiatry, also known as consultation-liaison psychiatry, is a subspecialty of psychiatry focused on the assessment, management, and follow-up of mental disorders that arise in the context of non-psychiatric medical conditions, particularly in general hospitals. Its goal is to integrate psychological, psychiatric, and social aspects into medical care, working in collaboration with other clinical services to improve patient outcomes [1].
This discipline is based on the biopsychosocial model proposed by George Engel in 1977, which acknowledges that health and illness are not solely determined by biological factors, but also by the individual's psychological and social components [2]. The evolution of medical thinking has moved from a traditional biomedical paradigm to a more integrative biopsychosocial model that is sensitive to the patient's subjective experience.
In this context, a comprehensive approach to medical-surgical patients is essential, especially in highly complex settings such as tertiary care hospitals. The presence of psychiatric disorders in hospitalized patients can significantly affect prognosis, treatment adherence, the doctor-patient relationship, and length of hospital stay [3,4]. Therefore, the systematic inclusion of liaison psychiatry in the multidisciplinary team enables more humane, effective, and patient-centered care.
Internationally, the origins of this subspecialty date back to the early 20th century with the development of psychosomatic medicine. In 1942, the Academy of Psychosomatic Medicine (APM) was founded in the United States. Later, in 2018, the organization officially adopted the name Academy of Consultation-Liaison Psychiatry (ACLP), reflecting a conceptual and operational shift toward a more clinical, integrated, and interdisciplinary collaborative approach [1]. Liaison psychiatry was officially recognized as a subspecialty by the American Board of Psychiatry and Neurology (ABPN) in 2004, solidifying its academic and professional development.
In Mexico, liaison psychiatry has evolved within tertiary hospitals. For over a decade, university-level advanced specialty training programs have been endorsed by the National Autonomous University of Mexico (UNAM). The first institution to formally establish such a course was the National Institute of Medical Sciences and Nutrition “Salvador Zubirán”. Subsequently, the University Hospital of Tecnológico de Monterrey, the Hospital Ángeles Pedregal affiliated with La Salle University, and the Centro Médico Nacional “20 de Noviembre” (ISSSTE) joined in. The latter has offered this program since 2018, becoming a key training site for subspecialists within the National Health System. Since 2023, these institutions have collaborated to enhance the academic training of their medical residents by actively participating in shared classes and academic sessions. These programs have strengthened the academic and clinical development of the subspecialty in response to the growing need for specialized care in hospitalized patients with medical-psychiatric comorbidity.
In 2018, the service consolidated its academic development through the formal creation of the Advanced Specialty Course in Liaison Psychiatry, endorsed by the National Autonomous University of Mexico (UNAM). This course was developed in response to the growing need for specialists trained in the comprehensive care of hospitalized patients with medical-psychiatric comorbidity, and to reflect the national and international recognition of the consultation-liaison model as a cornerstone of care in tertiary general hospitals. From its inception through 2025, the program has graduated nine fellows and currently trains five more. These professionals are now working in both public and private healthcare institutions, contributing to the strengthening of interdisciplinary care and the biopsychosocial model in a variety of hospital settings.
In 1994, following the institutional reorganization of the newly established Centro Médico Nacional “20 de Noviembre” (ISSSTE), the service was formally integrated into the Division of Neurosciences, alongside neurology, neurosurgery, neurophysiology, psychology, neuropsychology, and child and adolescent psychiatry (paidopsychiatry). This organizational structure was based on three fundamental pillars: clinical care, teaching, and research—thus consolidating an interdisciplinary model oriented toward the comprehensive care of hospitalized patients [5].
Current Organization of the Liaison Psychiatry Service
The Liaison Psychiatry area, within the Psychiatry Department of the Centro Médico Nacional “20 de Noviembre”, operates under a comprehensive model that includes both inpatient and outpatient care. It focuses on the biopsychosocial approach to patients with medical-surgical conditions and psychiatric comorbidity. The service is part of the clinical team of a high-specialty hospital and provides continuous coverage through morning, evening, and on-call shifts, including weekends and holidays.
In the inpatient setting, consultation requests are received from nearly all hospital departments, including Internal Medicine, Emergency, Oncology, Surgery, Intensive Care, Geriatrics, Nephrology, and Infectious Diseases, among others. Common reasons for referral include acute behavioral changes (delirium, agitation), suicide risk assessment, reactions to severe somatic diagnoses, evaluation of decision-making capacity, treatment adherence issues, and affective or anxiety symptoms in the context of medical illness. Care is provided promptly, following defined clinical and ethical protocols, and includes diagnostic evaluation, pharmacological and psychotherapeutic management, as well as recommendations to the treating team.
In the outpatient area, the service follows up on discharged patients who require continued psychiatric care, as well as referrals from other specialties in the hospital’s outpatient clinics.
In addition to its clinical work, the service actively participates in interdepartmental clinical rounds, literature review sessions, and case discussions with medical residents and staff from other specialties. Psychoeducation activities are also carried out for patients and families, with the aim of improving understanding of mental health conditions, promoting treatment adherence, and reducing stigma associated with psychiatric care. Family involvement is encouraged as part of the therapeutic process, particularly in cases of chronic illnesses, prolonged hospitalizations, or high-risk situations.
This organizational model supports patient-centered care, promotes interdisciplinary collaboration, and reinforces the role of mental health as an essential component in tertiary medicine.
Institutional Outcomes
In recent years, the Psychiatry Department at the Centro Médico Nacional “20 de Noviembre” has shown sustained growth in clinical activity, academic participation, and the training of human resources. The demand for psychiatric consultations has increased significantly, reflecting institutional recognition of the importance of addressing mental health in hospitalized patients.
Hundreds of consultation requests are received annually from various medical and surgical departments. The most frequent diagnoses include delirium, adjustment disorders, depressive and anxiety syndromes, psychotic disorders in medical contexts, as well as evaluations for suicide risk and treatment adherence challenges. In internal medicine and oncology patients, depressive syndromes associated with chronic or terminal illnesses are commonly addressed. In surgical areas, referrals often involve postoperative agitation, confusion, or behavioral decompensation.
Cumulative clinical data show that early psychiatric intervention improves patient understanding of their diagnosis, enhances treatment collaboration, and reduces average length of hospital stay, positively impacting institutional efficiency and healthcare costs.
In 2024, the Psychiatry Department maintained consistent and sustained clinical activity, as reflected in monthly medical productivity reports. Over 1,100 inpatient consultations, more than 13,000 outpatient visits, and approximately 1,100 evaluations during hospitalization were recorded—establishing the service as a high-demand unit within the institution.
Consultations were concentrated in departments such as internal medicine, oncology, geriatrics, general surgery, and emergency care. The most frequent diagnoses included delirium, depressive episodes, organic anxiety disorders, insomnia, and adjustment disorders—often in the context of complex medical or postoperative conditions.
| Diagnosis | Frequency | Percentage (%) |
| Delirium (F05) | 322 | 29.2% |
| Depressive Episode (F32) | 291 | 26.4% |
| Organic Anxiety Disorder (F06.4) | 224 | 20.3% |
| Insomnia (F51) | 159 | 14.4% |
| Adjustment Disorders (F43) | 53 | 4.8% |
| Others (schizophrenia, panic, delusional, etc.) | 55 | 4.9% |
This profile reflects the high burden of psychiatric comorbidity among hospitalized patients, particularly in critical care and surgical units.
Participation in Specialized Clinical Protocols
The service actively participates in high-complexity clinical protocols, contributing to the comprehensive assessment, follow-up, and psychosocial support of patients in the following areas:
- Bariatric Surgery: In 2024, over 60 pre-surgical evaluations were conducted, many in patients with eating disorders (ED) or affective comorbidities. Emotional follow-up is also provided post-surgery.
- Bone Marrow and Solid Organ Transplants (liver and kidney): Active participation in clinical committees for pre-transplant assessment and post-transplant monitoring in patients with emotional risk factors or previous psychiatric disorders.
- Functional Neurosurgery (Parkinson’s disease, epilepsy, movement disorders): Support for neurology and neurosurgery teams in selecting candidates for deep brain stimulation, with a strong emphasis on cognitive and emotional evaluation.
- Assisted Reproduction: Assessment of psychosocial factors in couples undergoing in vitro fertilization techniques. Over 40 patients were seen in the last quarter alone.
- Obsessive-Compulsive Disorder, Eating Disorders, and Addictions: The liaison psychiatry team collaborates in the design and implementation of interdisciplinary protocols alongside psychology, neuropsychology, and clinical psychiatry.
These actions reflect the service’s commitment to a biopsychosocial, interdisciplinary, and patient-centered care model, reaffirming its role as a vital bridge between specialized medicine and mental health.
Care in these settings enables timely, multidisciplinary intervention, improving treatment adherence, reducing surgical risks, and contributing to comprehensive, patient-centered care.
Academic Activity and Institutional Development
Academically, the service actively contributes to the training of psychiatry residents and provides cross-disciplinary education to residents from other specialties. The Centro Médico Nacional “20 de Noviembre” currently serves as the academic site for the Advanced Specialty Course in Liaison Psychiatry, endorsed by UNAM, positioning it as a leading training center for subspecialists in this discipline.
The service has also supported the development of specialty theses, participation in scientific conferences, and publication of clinical articles—reinforcing its profile as both an academic and research unit. This productivity has been made possible thanks to a multidisciplinary team committed to continuous improvement in patient care and knowledge generation in the field of hospital psychiatry.
Teaching and Research
Liaison Psychiatry at the Centro Médico Nacional “20 de Noviembre” not only fulfills a clinical role, but has also established itself as a key pillar in academic training and scientific production within the field of hospital mental health.
In the educational field, the service plays an active role in the clinical training of residents in Psychiatry, Child and Adolescent Psychiatry, and Liaison Psychiatry—both from direct-entry and advanced specialty programs. Since 2018, the hospital has offered the Advanced Specialty Course in Liaison Psychiatry, endorsed by the National Autonomous University of Mexico (UNAM), with a curriculum designed to develop clinical, ethical, and academic competencies for the comprehensive management of hospitalized patients with psychiatric comorbidities.
Residents rotate through the service at different stages of their training, receiving instruction in consultation skills, diagnostic evaluation, therapeutic planning, and interdisciplinary communication. Critical discussion of scientific literature is promoted through journal clubs, along with complex clinical case analysis and training in brief psychotherapeutic techniques applicable to hospital settings.
In research, the service has supported the development of specialty and subspecialty theses, focusing on topics such as delirium, treatment adherence, suicide risk management in medical patients, and the impact of psychiatric intervention on clinical indicators such as length of hospital stay and readmission rates.
Members of the service have also participated in national and international conferences, presenting clinical cases, research protocols, and teaching-clinical integration experiences. This close link between clinical care, education, and research reinforces the service’s identity as a national reference center in Liaison Psychiatry.
A major milestone in the academic trajectory of the service is the Liaison Psychiatry Monographic Course, first held in 2019. Its goal is to provide structured, practical, and accessible updates on key topics in psychiatric consultation and biopsychosocial models applied to hospital settings. Initially conceived as an internal teaching tool for ISSSTE residents and staff physicians, the course has grown significantly in content and reach. In 2025, it will celebrate its seventh consecutive edition, consolidating its place as a national academic reference event. Its impact has extended beyond the hospital through broadcasts and recordings on platforms like YouTube, where it has reached thousands of mental health professionals in training or clinical practice. This course has helped strengthen the service’s identity as a training center, promoter of modern hospital psychiatry, and generator of knowledge in consultation and liaison psychiatry.
Discussion
The experience of the Centro Médico Nacional “20 de Noviembre” in Liaison Psychiatry reflects Mexico's progress toward more comprehensive, interdisciplinary, and patient-centered medical care in alignment with international standards. According to the Academy of Consultation-Liaison Psychiatry (ACLP), this subspecialty primarily aims to care for patients with medical-psychiatric comorbidity, promote the integration of mental health into general medicine, and support both patients and clinical teams in general hospitals [1].
The CMN “20 de Noviembre” model aligns with these principles by maintaining continuous care at multiple levels: hospitalization, outpatient consultation, crisis intervention, and family involvement. In addition, formal training through a university-endorsed advanced specialty course positions the service not only as a clinical provider, but as a trainer of subspecialists skilled in complex diagnostic evaluation, interdisciplinary approaches, and ethical management of hospitalized patients.
The observed clinical outcomes are consistent with benefits described in international literature: improved diagnosis, greater treatment adherence, reduced hospital stays, and a better doctor-patient relationship [2,3]. The service has also identified areas for improvement, such as the need to standardize protocols, encourage psychoeducation among clinical departments, and promote applied research.
Furthermore, the biopsychosocial model proposed decades ago by George Engel [4] is especially relevant in this context, as it integrates the patient's subjective experience with clinical and social data essential for treatment. This approach has become indispensable in light of the increase in chronic illnesses, an aging population, and post-pandemic mental health challenges.
However, challenges remain. Stigmatization of psychiatric patients, institutional resistance in some departments, and clinical workload burdens are barriers that limit the full potential of Liaison Psychiatry. Overcoming these obstacles requires not only clinical commitment, but also institutional support, integrative hospital policies, and continued academic advancement.
In this regard, the experience of CMN “20 de Noviembre” represents a best-practice model within the Latin American context—one that may be replicated or adapted in other tertiary care hospitals aiming to optimize care for patients with complex medical conditions and concurrent psychiatric needs.
Conclusions
The experience of the Liaison Psychiatry Service at the Centro Médico Nacional “20 de Noviembre” highlights the high value of interdisciplinary approaches in contemporary medical care. The systematic integration of psychiatric assessment and management for medical-surgical patients has improved hospital care quality, optimized institutional resources, and promoted more complete recovery for patients.
Collaborative work with departments such as Internal Medicine, Oncology, Emergency, and Intensive Care has shown that including the liaison psychiatrist on clinical teams not only improves treatment adherence and prognosis but also strengthens doctor-patient communication and significantly reduces emotional factors affecting the course of medical illnesses.
In light of current mental health challenges, it is crucial to consolidate the role of the liaison psychiatrist as a central figure within the care model of tertiary hospitals. Their specialized training, capacity for timely intervention, and comprehensive approach make this subspecialty an indispensable component of a more humane, effective, and cost-efficient medicine.
The institutionalization of the university-level advanced specialty course and the observed clinical outcomes support the ongoing strengthening of such programs, the promotion of applied research, and the replication of successful models in other healthcare units across the country.
References
- Academy of Consultation-Liaison Psychiatry (ACLP). What is C-L Psychiatry? [Internet]. Available from: https://www.clpsychiatry.org/about-aclp/whatis-clp/
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- Engel GL. The need for a new medical model: a challenge for biomedicine. Science. 1977;196(4286):129–36.
- Valencia Granados FJ, Soriano Pérez ÁM. Structure and Function of the Psychiatry Service at CMN “20 de Noviembre” ISSSTE: An Analysis of Daily Practice. Revista de Especialidades Médico-Quirúrgicas. 2004;7(2):39–41.