Effect of addition of anti-inflammatory medication to anti-depressant medication in the treatment of depression

This study is a randomised controlled treatment (RCT) trial over 8 weeks, with a 6 month post-RCT trial period, where study participants have the option to continue Vortioxetine in the post-RCT trial period. The study aims to investigate whether the use of a blood test of inflammation levels, prior to antidepressant treatment, can improve treatment of depression by guiding the decision to add anti-inflammatory medication to antidepressant treatment. Specifically, the study aims to find out whether adding the anti-inflammatory medication Celecoxib to the antidepressant medication Vortioxetine can improve symptoms of depression. At the start of the study, participants would undergo a blood test to measure levels of the inflammatory marker C-reactive protein (CRP). For CRP, a cut-off level of 3mg/L will be used to determine whether participants are assigned to the "Depression with inflammation" arm, or to the "Depression without inflammation" arm. Within each study arm, participants would then be randomly assigned to 6 weeks of treatment with Vortioxetine plus Celecoxib, or Vortioxetine plus placebo. All study medications are oral tablets. The dose of Vortioxetine is initially 5 mg daily in those receiving Celecoxib, with an option to increase to Vortioxetine 10mg daily 2 weeks into the study (after review by the Psychiatrist, and if it is thought this dose may benefit the study participant). The planned dose of Celecoxib is 400mg daily. Study participants will be asked at each visit if any doses of study medication have been missed.