The scale of the underlying clinical problem is difficult to overstate. Estimates suggest that between 30 and 70 percent of psychiatric patients have a co-existing substance use disorder, and a nationwide Danish registry study found a lifetime prevalence of substance use disorder of roughly 30 percent among all patients in contact with psychiatry. A Cochrane review cited in the study indicates dual diagnosis may be present in up to 75 percent of patients with severe mental illness, and nearly half of admitted male psychiatric patients could be identified as having the condition—though significant underreporting is suspected. The two conditions interact destructively: each worsens the trajectory and outcomes of the other, and the consequences ripple beyond psychiatry into somatic health care and social life. Yet in Denmark, as in many countries, the treatment system is structurally split. A 2007 structural reform delegated responsibility for substance use treatment to Denmark’s 98 municipalities, while psychiatric care remains under the jurisdiction of the five hospital-governing Regions. The result is a system in which patients are routinely told to stabilize their psychiatric illness before entering addiction treatment, or vice versa—a deadlock the literature memorably describes as the “chicken or the egg” dilemma.

Traditionally, dual diagnosis treatment has been delivered in one of three ways: sequentially, treating one condition at a time; in parallel, treating both simultaneously through separate providers in separate systems; or in an integrated fashion, treating both simultaneously within a single system. Integrated treatment is widely regarded as best practice, and Integrated Dual Diagnosis Treatment (IDDT) is among the most evidence-based approaches. But Danish legislation from September 2024 mandates integrated treatment in psychiatry only for a small subset of the most severe cases—estimated at 9,200 individuals. The vast majority of patients with moderate to severe dual diagnosis will continue through sequential or parallel pathways. It was for this large group that the Capital Region developed the SPOR coordination model in 2021, using a “Model Cell” methodology—a small test center in which planning, testing, evaluation, and adaptation proceed systematically. The model’s guiding principle is “No Wrong Door”: regardless of where a patient enters the system, rejection should be avoided and linkage to the opposite sector provided.

SPOR comprises four components. First, screening: all patients in the region’s Flexible Assertive Community Treatment (FACT) teams are screened for problematic substance use with the AUDIT and/or DUDIT instruments, embedded directly in the electronic patient record, while municipal addiction centers use conversation-based approaches drawing on the Addiction Severity Index. Second, motivation: staff use Motivational Interviewing and Cognitive Behavioral Therapy techniques to encourage patients to enter treatment in the opposite sector. Third, companionship: with patient consent, a contact person physically accompanies the patient from one sector to the other to initiate treatment. Fourth, coordination: at least three network meetings should be held during a patient’s trajectory, with the opposite sector informed before treatment ends. These meetings bring together at least two professionals from different fields, plus the patient and possibly relatives, to agree on a coherent treatment plan.

To understand how this model fared in practice, the research team conducted 24 semi-structured interviews—16 individual and 8 group interviews—between April and October 2023, with staff from six FACT teams and five municipal substance use treatment facilities. Participants ranged from nurses and social workers, who formed the majority, to addiction counselors, psychologists, doctors, physiotherapists, occupational therapists, psychotherapists, and nursing assistants, with professional experience ranging from one to 36 years. The interview guide and analysis were structured around the Consolidated Framework for Implementation Research (CFIR), the most widely used determinant framework in implementation science, combined with Qualitative Content Analysis. Transcripts were divided into meaning units, condensed, and deductively categorized into CFIR’s five domains: Innovation, Outer Setting, Inner Setting, Individual Characteristics, and Implementation Process.

Across all five domains, the overall verdict on SPOR was positive. Staff in both sectors described the model as a relative advantage over previous fragmented collaboration, praised its practical concreteness, and noted it was less burdensome than earlier attempts at cross-sector work. The screening component, aided by its integration into electronic medical records, was progressing steadily in the psychiatric teams, though some staff worried that asking about drug use at a first meeting could jeopardize the therapeutic relationship, given patients’ fears that disclosure might exclude them from care. Companionship—physically walking patients to the opposite sector—was described as resource-intensive but a genuinely worthwhile investment. “Many of our clients have experienced multiple system failures, so good relations are truly significant to them,” one addiction treatment staff member told the researchers. Network meetings were valued for building mutual understanding and patient security, even though they demanded significant preparation time and still fell short of the target of three per patient. Coordination at the point of treatment discharge emerged as the weakest link, with staff citing heavy caseloads and the absence of an established routine.

Beneath the positives, however, the interviews exposed stubborn structural and cultural barriers. A striking realization reported by several participants was the extent of “double work”: the problems discussed in addiction treatment—everyday chaos, lack of structure, goals—are almost identical to those discussed in psychiatry, suggesting substantial unexploited common ground. Yet knowledge of each other’s competencies and services remains thin. Staff in psychiatry admitted they had little idea what addiction treatment centers looked like or who worked there, while addiction staff found the referral-based psychiatric system rigid and slow to access. A deeper cultural divide concerned treatment philosophy: psychiatry’s long-standing requirement of three months’ abstinence before initiating treatment is gradually yielding to a harm-reduction approach under SPOR, but the shift demands sustained behavioral change. Addiction centers, where harm reduction is already embedded, in turn criticized psychiatry for rejecting patients who continue to use substances. “A diabetic can have ice cream. A patient with lung disease is allowed to go smoke. Why can’t addicts be treated the same way?” one participant asked, unintentionally illustrating how stigmatizing language persists even in supportive arguments.

Staff competence emerged as perhaps the most consistent deficit. Despite implementation strategies aimed at knowledge and skills, workers in both sectors reported feeling inadequately equipped to treat dual diagnosis patients: addiction staff wanted training in psychiatric diagnostic criteria and clinical presentations, while psychiatric staff wanted education on substance use disorders and how to address them. Patients who failed to attend appointments were still at risk of being labeled “not motivated” and having treatment terminated—a form of what implementation scholars call “creaming,” in which services flow to those deemed easiest to help. The researchers interpret such decisions through Michael Lipsky’s concept of street-level bureaucracy: frontline workers, squeezed by resource constraints and performance demands, quietly ration services, and the sector boundary becomes the place where these structural pressures are expressed as mutual gatekeeping, with each side accusing the other of ending treatment too soon.

The implementation process itself offered instructive lessons. A project management team and a cross-sector secretary acted as champions, and staff highlighted the psychological safety fostered by leaders who permitted open admission of knowledge gaps and insecurities. Repetition, reminders, and concrete practical tools—action cards, guidelines, posters with contact details—were repeatedly requested, and some initially skeptical staff came to appreciate the high frequency of follow-up meetings. Yet enthusiasm was tinged with concern about a recent drift from participatory involvement toward top-down steering, with one participant complaining that only managers now met and frontline staff were no longer updated. Participants cautioned against premature scaling of SPOR until existing barriers were addressed, warned of implementation fatigue from competing initiatives, and proposed structured onboarding for new staff, reinforced narratives, prioritization of physical cross-sector meetings, concrete how-to guidelines, and a shared cross-sector conference forum for discussing difficult cases.

The study’s authors conclude that sustainable cross-sector collaboration in dual diagnosis care requires extensive management support, ongoing attention to culture and behavior change, and a systematic enhancement of staff competences in detecting and treating the condition. The SPOR model, they find, has demonstrably improved coordination practices and dismantled some of the routine rejection of dual diagnosis patients—but patients were still turned away, flexibility remained hard to achieve under time and staffing pressures, and the gap between managerial ambition and frontline capacity persists. For health systems worldwide grappling with the same fragmentation, the Danish experience offers a sober but hopeful message: bridging psychiatry and addiction treatment is less a matter of designing an elegant model than of investing, patiently and continuously, in the people expected to carry it across the divide.