Weight loss prior to diagnosis of first-episode psychosis predicts subsequent weight gain: a retrospective cohort study of the UK Clinical Practice Research Datalink (CPRD) primary care database.

BACKGROUND

Post-psychosis weight gain is commonly rapid, yet prediagnosis weight changes are under-researched. The untreated phase of first-episode psychosis (FEP) can be characterised by behaviour which could lead to weight loss, triggering physiological adaptations which prime the body to regain weight.

OBJECTIVE

We aimed to investigate the prevalence and extent of weight loss prior to diagnosis of FEP, and to investigate its impact on subsequent weight gain.

METHODS

We used Clinical Practice Research Datalink primary care data, supplemented with linked hospital episode statistics, ethnicity and deprivation data to estimate pre-FEP weight loss prevalence. We then used multiple linear regression to assess its association with subsequent weight change, while adjusting for relevant confounders.

FINDINGS: Primary analysis included 369 individuals with adequate data. 53% of individuals experienced weight loss before FEP. Using percentage weight change as an outcome, individuals with pre-FEP weight loss gained weight post-FEP at over twice the rate of those without prior loss (8.93% (95% CI 6.90% to 10.96%) bodyweight per year vs 4.07% per year (95% CI 1.90% to 6.24%); p=0.005). Each 1% of pre-FEP weight loss predicted 0.41% (95% CI 0.23% to 0.59%) additional annual weight gain (p=0.004), most pronounced within 6 months and independent of antipsychotic treatment selection. Using kilogram per year as an outcome, average gain (6.49 kg (95% CI 5.28 kg to 7.70 kg)) exceeded average prior loss (4.83 kg (95% CI 4.00 kg to 5.66 kg)) by 1 year. Findings were robust across sensitivity analyses.

CONCLUSIONS

Pre-FEP weight loss is common and predicts rapid post-diagnosis gain. While all patients were expected to gain weight, those with pre-FEP weight loss gained double the weight of those who had not lost weight.

CLINICAL IMPLICATIONS: Clinicians treating individuals with FEP should enquire about weight loss in the pretreatment period, which predicts extra weight gain in the initial period following diagnosis. This could inform early intervention to avoid consequences of short-term weight gain.