Objective To investigate equity of patient outcomes in a psychological therapy service, following increased access achieved by a quality improvement (QI) initiative.

Design Retrospective service evaluation of health outcomes; data analysed by ANOVA, chi-squared and Statistical Process Control.

Setting A psychological therapy service in Westminster, London, UK.

Participants People living in the Borough of Westminster, London, attending the service (from either healthcare professional or self-referral) between February 2009 and May 2012.

Intervention(s) Social marketing interventions were used to increase referrals, including the promotion of the service through local media and through existing social networks.

Main Outcome Measure(s) (i) Severity of depression on entry using Patient Health Questionnaire-9 (PHQ9). (ii) Changes to severity of depression following treatment (ΔPHQ9). (iii) Changes in attainment of a meaningful improvement in condition assessed by a key performance indicator.

Results Patients from areas of high deprivation entered the service with more severe depression (M = 15.47, SD = 6.75), compared with patients from areas of low (M = 13.20, SD = 6.75) and medium (M = 14.44, SD = 6.64) deprivation. Patients in low, medium and high deprivation areas attained similar changes in depression score (ΔPHQ9: M = −6.60, SD = 6.41). Similar proportions of patients achieved the key performance indicator across initiative phase and deprivation categories.

Conclusions QI methods improved access to mental health services; this paper finds no evidence for differences in clinical outcomes in patients, regardless of level of deprivation, interpreted as no evidence of inequity in the service with respect to this outcome.