The organization of psychiatric services for general hospital departments might change in far-reaching ways in the coming decades. Whereas the focus was primarily on reactive services for inpatients on medical and surgical wards, the future should focus on more proactive integrated service delivery for the complex medically ill. The essential difference from other psychiatric services is that the population served is taken care of by medical specialists in the general health setting. Consequently services are delivered in the context of the medical-psychiatric interface. Consult requests are always formulated in this perspective: the patient is treated for a medical illness or physical complaints and there are signs of an interfering psychiatric disorder.1 Nowadays these patients are referred to as the ‘complex medically ill’.⁽¹⁾ Therefore triage and treatment integrated in the medical context is the area of expertise of consultation-liaison (CL) psychiatrists.

The development of this area of psychiatry has been hampered by dysfunctional splits in health care, such as between general and mental health care, both on the level of its organization as well as its reimbursement.^(2,3) Recent reports, such as the report of the joint working group of the United Kingdom Royal College of Physicians and the Royal College of Psychiatrists, which describe the psychological needs of the medically and surgically ill, provide guidance to counteract these dysfunctional splits.⁽⁴⁾ As the delivery of care-trajectories for comorbid patients becomes more and more an issue on the health care agenda, CL psychiatrists should seize this opportunity and become advocates for integrated service delivery for the complex medically ill.

¹Whereas in mental health comorbidity refers to making more than one criteria based psychiatric diagnosis, in the CL literature the term ‘comorbidity’ is generally used to describe the combination of physical diseases and psychiatric disorders.

Around 1990 the extent of inpatient CL psychiatric service delivery was evaluated, based on the records of a representative national sample of hospitals (United States)⁽⁵⁾ and based on a prospective multicentred study (Europe).⁽⁶⁾ Both studies reported an average consult rate of 1 per cent, ranging up to 4-5 per cent in some university settings. This rate is much lower than the prevalence of psychiatric disorders in medical populations.⁽⁶⁾ Taking this underutilization into account, the most striking finding was still the large variation in departments served and types of patients seen. The European Consultation-Liaison Workgroup’s (ECLW) Collaborative Study made clear that CL psychiatric service delivery is primarily an emergency service. Most referrals were late, as reflected by an average time of 11 days after admission before patients were referred. In addition one-third was emergency referrals: ‘See the patient the same day’.^{(6, 7)} Exceptions were the German psychosomatic services driven by their primary interest in patients with unexplained physical complaints and problems of coping with somatic illness using a more integrated liaison approach. These services showed higher consultation rates (between 2 and 4 per cent), provided more follow-up visits, and communication with aftercare providers.^{(6, 7, 8 and 9)}

It is now evident that mental disorders and physical diseases cluster in vulnerable patients. The prevalence of mental disorders in the general hospital population is on average twice as high compared to that of the general population. However, when focusing on specific populations such as cardiac, diabetes, or transplantation, the rates of major depression may reach up to 30 per cent^{(10, 11)} (see other chapters of this section). Patients in the general hospital setting are primarily treated for their physical diseases. However, the multiple interactions between the comorbid medical and psychiatric disorders make them complex. This justifies an integrated approach and requires individualized multimodal and multidisciplinary care.^(12,13) These complex patients are the target population for CL psychiatrists. They are in need of integrated services.

Here several models of service delivery are described (Table 5.7.1). The models have an increasing level of sophistication determined by their level of integration and the related procedural collaborative activities. Service delivery requires by definition, negotiations with health plans for their reimbursement. This is especially true for the integrated models of service delivery.^(7,13,14)