Uncovering variations in depression symptom change across ethnic groups during psychological intervention could improve understanding of differences in treatment response. This study aimed to: (1) identify trajectories of change in treatment; (2) ascertain if depression symptom trajectories varied between BAME and White populations; (3) investigate if sociodemographic and treatment variables predicted association with the identified trajectories; and (4) examine if ethnic groups predicted different trajectory memberships. Adults (N = 17109) with depression and recorded ethnicity were included in the analysis. Depressive symptoms were measured using the Patient Health Questionnaire-9, and co-occurring anxiety was measured using the Generalised Anxiety Disorder-7. Growth Mixture Modelling (GMM) was employed to identify trajectories of symptom change, and multinomial logistic regressions were used to identify ethnicity and other pre-treatment variables associated with trajectory membership. GMM resulted in three depression trajectories of change and four anxiety trajectories. There was a high proportion of patients who did not respond to treatment. Pre-treatment variables that predicted Non-response were: ethnic minority, unemployment, deprived areas, prescribed medications, higher baseline anxiety and depression scores, and long-term physical health conditions. Asian patients had higher odds than White patients associated with trajectories that had high severity for both outcome measures. Black, Other, Mixed-heritage, and Chinese populations were no different from White populations in depressive treatment responses after adjusting for an index of multiple deprivations (IMD). Results have implications for identifying patients at risk of non-response such that clinicians can tailor culturally sensitive interventions for ethnic minority patients
