Weight gain in the months/years after diagnosis/treatment severe enduring mental illness (SMI) is a major predictor of future diabetes, dysmetabolic profile and increased cardiometabolic risk in people treated with antipsychotic agents. There is limited data on the longer term profile of weight change in people with a history of SMI and how this may differ between individuals. We here report a 25-year perspective on weight change post-SMI diagnosis in Greater Manchester UK, an ethnically and culturally diverse community, with particular focus on a history of psychosis vs bipolar affective disorder.

We undertook an anonymised search in the Greater Manchester Care Record (GMCR). We reviewed the health records of anyone who had been diagnosed for the first time with first episode psychosis, schizophrenia, schizoaffective disorder, delusional disorder (non-affective psychosis = NAP) also bipolar disorder = BPD). We analysed body mass index (BMI) change in the period before and after first prescription of anti-psychotic medication.

We identified 9125 people with the diagnoses above. NAP (n = 5618; 37.5% female) mean age 49.3 years; BPD (n = 4131; 63.3% female) mean age 48.1 years. Follow-up period was up to 25 years. 27.0% of NAP were of non-white ethnicity vs 17.8% of BAP individuals.

A higher proportion of people diagnosed with NAP were in the highest quintile of social disadvantage 52.4% vs 39.5% for BPD. There were no significant differences in baseline BMI profile but mean HbA1c in those 2103 people where available was higher in NAP at baseline at 40.4mmol/mol vs 36.7mmol/mol for BPD.

At 5-year follow-up 53.6% of those NAP with a normal healthy BMI transitioned to obese / overweight BMI vs 55.6% with BPD. 43.7% of those NAP with normal BMI remained at a healthy BMI vs 42.7 % with BPD. At 5-year FU for NAP, 83.1% of those with BMI ≥30kg/m2 stayed in this category vs 81.5% of BPD.

At 5-year follow-up there was similarity in the overall % NAP in the obese ≥30kg/m2 category (42.4%) vs BPD (44.1%).

The results of this 25-year real world longitudinal cohort study suggest that the changes in BMI with treatment of non-affective psychosis vs bipolar disorder are not significantly different, highlighting the importance of regular physical health monitoring in all people with SMI.

Using longitudinal population data in this way has the potential to open up new avenues of research in psychiatry in terms of physical and mental health outcomes.