GPs will give patients a standard depression questionnaire at diagnosis and again 10 to 35 days later, then use the scores to guide treatment decisions. This matters because most GPs currently diagnose depression without a formal, validated tool. They rely on clinical judgment alone, which can miss severity or fail to track whether treatment is working. The PHQ-9 questionnaire is widely used in research but rarely in routine GP consultations. This trial tests whether embedding it into real appointments—with training for GPs on interpreting scores and discussing them with patients—actually improves outcomes. If the trial succeeds, routine NHS depression care could shift from subjective assessment to a structured, patient-reported monitoring system. Patients would receive written feedback on their scores and suggested treatments to discuss with their doctor. This could lead to more accurate treatment adjustments, fewer patients falling through the cracks, and better use of NHS resources. The trial also includes a cost-effectiveness analysis, so funders will know whether the approach saves money or improves quality of life for the roughly 676 patients and 113 GP practices involved across three centres.
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Design: Parallel group cluster randomised trial with 1:1 allocation to intervention and control. Inclusion: Patients age 18+ years, with a new episode of depressive disorder/symptoms. If possible, patients will be recruited opportunistically at consultations for new episodes of depression. Records will also be searched for newly presenting patients, to reduce the risk of selection bias. Exclusions: current depression treatment, comorbid dementia/psychosis/substance misuse/suicidal ideas. Intervention: Administration of PHQ-9 soon after diagnosis, and at follow-up 10-35 days later. We will target GP reflective motivation and psychological capability with guidance on assessment and treatment, informed by NICE guidelines. GPs will be trained in interpreting scores, along with asking open-ended questions and exploring the patient's life context, and asked to take them into account in their treatment decisions. Patients will be given written feedback on their scores and suggested treatments to discuss with GPs. Control practice patients will not complete the PHQ-9. They will complete research outcome measures but not be given feedback on the results. Baseline measures: depression on the Beck Depression Inventory BDI-II, sociodemographics, duration and past history of depression, GAD-7 for anxiety. Outcomes: Primary outcome: BDI-II at 12 weeks. Secondary outcomes: BDI-II at 26 weeks; changes in drug treatments and referrals; social functioning (Work & Social Adjustment Scale) & quality of life (EQ-5D) at 12 & 26 weeks; service use over 26 weeks (modified Client Services Receipt Inventory) to calculate NHS costs; patient satisfaction at 26 weeks (Medical Informant Satisfaction Scale). Sample size: Assuming baseline mean BDI-II 24.0; SD 10.0 (from feasibility RCT); follow-up mean of 14.0 at 12 weeks in intervention group, 17.0 in controls (difference 3.0 = effect size of 0.3 and MCID of 17.5% of control group score); mean 6 patients per practice; ICC 0.03; 5% significance; 90% power; needs 235 patients analysed per group. Cluster design effect 1.15; assuming 20% loss to follow-up gives 235x1.15x2/0.8 =676 total, from 113 practices across three centres. Randomisation: by CTU statistician with computerised sequence generation. Blinding: of practitioners and patients is impossible given the nature of the intervention. Self-report outcome measures will prevent researcher rating bias. Analysis: Differences at 12 and 26 weeks between intervention and controls in depression, social functioning and quality of life will be analysed using linear mixed models, adjusted for sociodemographics, baseline depression, anxiety, and clustering, including practice as a random effect. Patient satisfaction, quality of life (QALYs) and costs over 26 weeks will be compared between arms. Qualitative process analysis: Interviews with 15-20 GP/NPs and 15-20 patients per arm to reflect on trial results and implementation issues, using Normalization Process Theory as a framework for the interview schedules and qualitative analyses. Practitioner/patient dyads to be interviewed as soon as possible after patient assessments at follow-up consultations, to explore recall of practitioner-patient discussion of scores and identify variations in the use of the PHQ-9.
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