Clearing and holding: a 26-month interrupted time-series evaluation of CAMHS waiting-list redesign in Qatar

Background Clearing a waiting list is not the same as keeping it under control. Evidence on the durability of child and adolescent mental health service (CAMHS) waiting-list interventions under continuing or rising demand is limited. We evaluated an initial waiting-list reduction and 20 months of subsequent maintenance. Methods We conducted an interrupted time-series service evaluation at a pediatric tertiary center in Qatar using 800 consecutive daily census observations from 10 June 2024 to 18 August 2026, supplemented by referral-order, follow-up activity, and annual access data. In December 2024, parallel queues were consolidated, triage accountability was centralized, historical referrals were revalidated, and clinical time was concentrated on first assessments. Recurring protected assessment blocks were later intensified. Segmented regression used Newey-West standard errors. Results The redesign was associated with a modeled level change of -381.0 patients (95% confidence interval: -412.8 to -349.2); at the change point, the counterfactual pre-intervention and fitted post-intervention values were 510.5 and 129.5, respectively. The census reached a trough of 31 in August 2025. Mean monthly unique referral orders increased from 215 during June-August 2025 to 347 during September-November 2025 (61%), coinciding with a rebound. Across 19 complete months, referral volume and mean census were not significantly correlated ( r = 0.24, p = 0.33). The mean census during September 2025-March 2026 was 126.3, 71% below the pre-intervention mean of 434.5, and returned to 115.1 during recovery. Conclusions The redesign was associated with a large and sustained reduction in the recorded waiting-list census without additional posts. Clearance required a concentrated backlog intervention, whereas maintenance required continuing monitoring and flexible protection of assessment capacity. Outcomes for patients removed through non-assessment pathways remain unknown.