Understanding the impact of bariatric surgery on patients with severe mental health illness

Bariatric surgery has been shown to be one of the most cost-effective and efficacious treatments currently available for obesity. However, a subset of patients struggle with significant psychological distress and increased care needs after bariatric surgery, including emergency hospital admissions, chronic pain, alcohol use disorder and increased psychological disorder. There was a common perception that pre-existing psychiatric disorder plays a role in post-operative outcomes, but no studies had been carried out in the UK to examine whether this is the case.

Our Discover depersonalised longitudinally linked dataset allowed us to carry out a retrospective study of patients undergoing bariatric surgery and examine the procedures effects on those with a psychiatric diagnosis, in partnership with West London Mental Health Trust. The results of this study could then help the healthcare system better allocate resources to support people undergoing bariatric surgery and assess whether psychiatric diagnosis is a useful indicator of greater support needs in this context.

Study aims

Understanding the post-operative outcomes for bariatric surgery

The aims of this study were to perform retrospective analysis of the longitudinal North West London Discover dataset to examine the correlation between psychiatric diagnosis, collected as part of routine NHS care, with health and social care usage following bariatric surgery.

Our hypothesis was:

Patients undergoing bariatric surgery with a psychiatric diagnosis at the time of surgery will have greater needs post operatively in terms of:

  • Healthcare usage, including A&E admissions;
  • Social care usage.


The benefits of linked data

The Discover dataset is an important advance in the provision of data banks in the UK as it contains linked coded data from primary care, secondary care, community, mental health and social care and is therefore uniquely able to provide a whole system view of the patient journey throughout their medical care. 

This means that, while all data is depersonalised, we are still able to see the outcomes for patients following their bariatric surgery, and also identify any pre-existing conditions when the surgery took place.

Using a five-year data period we split patients in North West London who had undergone Bariatric Surgery during the study period into three groups for comparison:

  • No Psychological Diagnosis;
  • Common Mental Illness, consisting of diagnoses of anxiety and depression;
  • Serious Mental Illness, consisting of diagnoses of schizophrenia, bipolar disorder, and personality disorder

Patients were classified as having a common mental illness diagnosis, or serious mental illness diagnosis if they had a Read or ICD-10 code indicative of the specified conditions prior to surgery.

Males and females between 18 and 80 were included in the study and all bariatric procedures were included, excluding revision or conversion procedures.

The Discover linked dataset enabled the following research activities:

  • Quantifying healthcare usage in primary care, secondary care and in the community and associated costs to compare across the study groups;
  • Quantifying social care usage to compare across the study groups;
  • Exploring patient demographics including age, sex, and ethnicity;
  • Exploring secondary outcomes of interest including: Smoking and Alcohol Use, Employment Status, BMI, Primary Care Prescriptions;
  • Exploring Comorbidities of interest including: Gastroesophageal Reflux Disease (GERD), Non-Alcoholic Fatty Liver Disease (NAFLD), Diabetes, Hypogonadism, Polycystic Ovaries Syndrome (PCOS), Joint Disease, Lipid Control, Cardiovascular Risk, Airway Disease.


In the first year after surgery the serious mental illness group have higher healthcare usage post operatively in comparison with the other two groups. Following surgery up to two years post operatively the serious mental illness and common mental illness groups have a reduction, or no significant increase in:

  •  A&E usage
  • Non elective admissions
  • Outpatient appointments
  • Mental health outpatients
  • Community contacts

Post-surgery all groups had a significant reduction in*:

  • BMI
  • HbA1C

*Up to 2 years post operatively


‘“This study allows us to better understand the care needs of people with serious mental health difficulties presenting for bariatric surgery.

“People living with obesity and serious mental illness face premature mortality and stigmatising attitudes from the public and healthcare professionals.

“This dataset allows us to objectively analyse long term healthcare usage in a number of settings, not only hospital, but also community care and GP appointments, before and after bariatric surgery so that we can objectively assess the benefits to our patients, thereby reducing the stigmatising attitudes they may face when presenting for bariatric surgery.

“By understanding the higher healthcare needs after surgery in this group we are also better able to plan their pre-surgery and aftercare with them and plan services accordingly.”

Dr Samantha Scholtz
Consultant Psychiatrist - Bariatric surgery, St. Mary’s Hospital Research and Development Director


If you would like to find out more about this work please email us.