Bariatric surgery is an effective treatment for severe obesity that leads to significant physical health improvements. Few studies have prospectively described the short-term impact of surgery on mental health using standardised case-finding measures for anxiety or depressive disorders. This study describes the prevalence and short-term course of these conditions following surgery.

Prospective observational cohort study.

12 National Health Service centres in England.

Participants studied took part in the By-Band-Sleeve study, a multicentre randomised controlled trial evaluating the surgical management of severe obesity. We included participants who had undergone surgery (gastric bypass, gastric band or sleeve gastrectomy) within 6 months of randomisation.

Anxiety and depression were assessed using the Hospital Anxiety and Depression Scale (HADS) at baseline and 12 months post-randomisation. Sociodemographic variables collected at prerandomisation included body mass index, age, sex, ethnicity, marital status, tobacco use, employment status and income band.

In our sample of 758 participants, 94.5% (n 716) and 93.9% (n 712) had completed baseline anxiety (HADS-A) and depression (HADS-D) subscales. At pre-randomisation 46.1% (n 330/716, 95% CI 42.4% to 49.7%) met clinical case criteria for anxiety and 48.2% (n 343/712, 95% CI 44.5% to 51.8%) for depression. Among participants returning completed 12 months post-randomisation questionnaires (HADS-A n 503/716, HADS-D n 498/712), there was a significant reduction in the proportion of clinical cases with anxiety (–9.5%, 95% CI –14.3% to -4.8% p

Almost half of people undergoing bariatric surgery had underlying anxiety or depressive symptoms. In the short term, these symptoms appear to substantially improve. Future work must identify whether these effects are sustained beyond the first post-randomisation year.

NCT02841527 and ISRCTN00786323.