Research Summary

Danish Primary Care Trials Find Collaborative Care Improves Long-Term Depression Outcomes Versus Consultation Liaison

Edited by:
Kate Young

Key Highlights:

  • In the depression trial, collaborative care produced lower depressive symptom scores at 18 months than consultation liaison.
  • In the anxiety trial, collaborative care did not significantly reduce anxiety symptoms at 18 months vs consultation liaison.
  • Across both trials, collaborative care groups had fewer contacts with private practicing psychologists over 18 months, while employment/education and sick-leave outcomes did not differ between groups.

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Eighteen-month follow-up from the Danish Collabri Flex program suggests that collaborative care in general practice may yield sustained advantages over consultation liaison for depressive symptoms in patients treated for depression, but not for the primary anxiety outcome in patients treated for anxiety disorders. The findings were published in Depression and Anxiety and extend previously reported 6-month outcomes by examining longer-term symptom, function, and healthcare-use measures.

Collabri Flex consisted of two pragmatic, investigator-initiated, parallel-group superiority randomized controlled trials conducted in general practices in the Capital Region of Denmark (recruitment January 2018–September 2019). Adults (≥18 years) speaking Danish with ICD-10 depression (F32/F33) or selected anxiety disorders (including social anxiety disorder, panic disorder, agoraphobia, generalized anxiety disorder, obsessive–compulsive disorder, and post-traumatic stress disorder; no PTSD participants were ultimately enrolled) were randomized to collaborative care or consultation liaison.

In consultation liaison, general practitioners (GPs) retained responsibility for care with optional advice from psychiatrists and/or care managers; patients had no care-manager contact after randomization. In collaborative care, a multiprofessional team (GP, psychiatrist, care manager trained in CBT) supported structured management, scheduled monitoring, and stepped-care treatment that could include psychoeducation, CBT, and medication. Outcomes at 18 months included depression (BDI-II), anxiety (BAI), well-being (WHO-5), disability (SDS), general psychological symptoms (SCL-90-R), self-efficacy and health status (EQ-5D-3L), remission, and register-based measures (employment/education, sick leave, outpatient mental health contacts). Analyses followed intention-to-treat principles with multiple imputation for missing questionnaire data and ANCOVA, logistic, and Poisson regression models adjusted for baseline values and stratification variables.

Study Findings

In the depression trial, collaborative care was associated with significantly lower depression symptom scores at 18 months than consultation liaison (BDI-II mean 12.3 vs 15.8; between-group difference 4.4; 95% CI, 2.8–6.1; P ≤ .001; Cohen’s d=0.37). Multiple secondary outcomes also favored collaborative care, including lower anxiety symptoms (BAI difference 2.9; 95% CI, 1.7–4.2; P ≤ .001), lower disability (SDS difference 2.7; 95% CI, 1.6–3.9; P ≤ .001), higher well-being (WHO-5 difference −9.7; 95% CI, −13.5 to −5.9; P ≤ .001), and lower general psychological symptoms (SCL-90-R difference 17.5; 95% CI, 10.1–25.0; P ≤ .001). Remission defined as BDI-II ≤13 occurred in 61.4% of collaborative care participants vs 49.1% with consultation liaison (OR 0.50; 95% CI, 0.29–0.87; P = .015). No differences were observed in employment/education or sick-leave measures, and psychiatric outpatient service contacts did not differ significantly.

In the anxiety trial, anxiety symptoms improved in both groups, but the between-group difference at 18 months was not statistically significant (BAI mean 14.0 vs 15.3; difference 1.2; 95% CI, −0.3 to 2.7; P = .126). However, depressive symptoms favored collaborative care at 18 months (BDI-II mean 9.8 vs 12.4; difference 2.8; 95% CI, 1.2–4.4; P ≤ .001; Cohen’s d=0.32), and general psychological symptoms were also lower with collaborative care (SCL-90-R difference 8.0; 95% CI, 0.2–15.8; P = 0.045). Functional level, well-being, self-efficacy, health status, remission (BAI-defined), employment/education, sick leave, and psychiatric outpatient contacts did not differ significantly between groups.

Clinical Implications

At 18 months, collaborative care maintained a statistically significant advantage for depressive symptoms in the depression-focused trial, while the primary anxiety outcome in the anxiety-focused trial did not show a significant between-group difference. The authors also noted that collaborative care groups in both trials had significantly fewer contacts with private practicing psychologists during follow-up, suggesting the model may have the potential to reduce referrals to a high-demand service in Denmark.

Limitations included response rates of 58% in the depression trial and 60% in the anxiety trial at 18 months with lower follow-up in consultation liaison groups, raising potential attrition bias concerns. The investigators did not collect registry data on medication use, limiting interpretation of whether pharmacologic differences contributed to outcomes. Heterogeneity of anxiety diagnoses was also noted as a potential challenge in detecting disorder-specific effects.

Expert Commentary

“At 18-month follow-up, we found a statistically significant difference between allocation groups, in favor of collaborative care, when measuring depression symptoms in the depression trial but not when measuring anxiety symptoms in the anxiety trial,” the researchers concluded. “At this timepoint, the collaborative care groups in both trials had significantly fewer contacts with private psychologists than did the consultation liaison groups. Thus, the intervention may also have the potential to reduce referrals to a service that is in high demand in Denmark.”

Reference:
Curth NK, Bjørkedal STB, Hjorthøj C, et al. Collaborative care versus consultation liaison for patients with depression or anxiety disorders in general practice in Denmark: 18-month follow-up from the Collabri Flex Trials. Depress Anxiety. 2025;2025:2909617. Published 2025 Jun 5. doi:10.1155/da/2909617