The Lancet Psychiatry Commission on Physical Health (Firth et al, 2019) has demonstrated the increased physical health risks that people with severe mental illness (SMI) are subject to. We know that people with SMI have an increased risk of physical disease, as well as reduced access to adequate health care, with disparities observed across all mental illnesses in all countries. Causes of an estimated fifteen to twenty year excess mortality, many of which have been discussed here, include cardiovascular disease and a doubling of rates of respiratory disease.
While concerning, these physical conditions offer opportunities to intervene to reduce their likelihood and impact. There has therefore been an increasing emphasis upon access to physical healthcare and screening for this population.
A known contributor to excess physical illnesses and mortality in this group is weight gain, which a new study has explored over a fifteen-year period (Lee et al, 2025). The study also reviewed access to weight management services in two cohorts to assess whether interventions were being made available to people with SMI compared to the general population.
This study adds yet more evidence to the case for these risks to be more widely recognised and again emphasises the urgent need for appropriate early interventions to be put in place.
Weight gain is a known contributor to excess physical illnesses and mortality among people with serious mental illness diagnoses.
Methods
This was a population-based matched cohort study using data from the Clinical Practice Research Datalink Aurum, which is a database containing electronic health records from UK primary care practices that use EMIS Web software. Over 100,000 records of people aged between 18 and 65 were included from 1,454 primary care practices across England. 20% had a diagnosis of a severe mental illness (schizophrenia, bipolar or other psychosis) and each was matched using demographic characteristics to four others from the same practice who had never been diagnosed.
All individuals were tracked for up to fifteen years – either up to the date of them leaving the practice, or the date of their death, or the full fifteen-year period. The researchers tracked changes in weight, as well as whether advice or referral to weight management services were given. A linear regression model was then used to compare weight gain between the cohorts, while a Poisson regression model compared rates of weight management advice and referral to services.
The study was based on a large sample of UK primary care health records: 100,000 records over a 15 year period.
Results
Records for 113,904 people were included in the analyses with an average age of 39. 45% were male and 55% female. Over the 15-year follow-up period, the SMI group had on average 19 weight measurements, whereas those without had an average of 15 measurements.
Weight gain findings
The study concluded that those with SMI experienced significant weight gain over the study period of up to fifteen years.
On average, weight increased for the SMI group by 2.1kg after the first year, 4.9kg after five years and 5.6kg after fifteen years. This compared to 0.6kg, 1.6kg and 1.62kg over the same periods in the control group.
Rapid weight gain was notable in the initial five years after diagnosis, with people with SMI gaining 3.2 kg more than the matched non-SMI group.
Other notable findings included:
- Increased weight gain for people with a schizophrenia diagnosis (6.9kg) compared to those with a diagnosis of bipolar (4.3kg) over fifteen years.
- Weight gain was found to be higher among users of antipsychotic medications, with the greatest weight gains found in those who had used antipsychotics for the longest.
- There was little evidence found of differences between first and second generation antipsychotics or for those who used combinations of more than one drug.
- Younger individuals (aged 40 or younger) with SMI showed steeper weight gain trajectories than average.
- Weight gain did not vary by race and ethnicity or socioeconomic status (except for people without severe mental illness in deprived areas, who had steeper trajectories than people without severe mental illness in the least deprived areas).
Weight advice and management referral findings
27% of those with SMI were shown to have received weight management advice compared with 23% of the non-SMI cohort. After adjusting for a number of potentially confounding variables, people in the SMI group were found to be 10% more likely to receive weight management advice than those in the non-SMI group.
Referrals to weight management services were much less common and rates were low in both groups. Only 4.5% of SMI and 2.7% of non-SMI patients recorded as receiving referrals. There was no evidence of significantly higher rates of referral to weight management programmes among people with SMI compared to the comparison group.
Referrals for weight management were low across both groups
Conclusions
It is clear from this study that those with SMI experience significantly higher weight gain, particularly in the early years after diagnosis. With an average gain that is over three times that recorded among the matched cohort without SMI. This is a stark finding. People with lived experience of mental ill health have long known this to be the case, and the study provides clear research evidence for this belief. As the authors conclude:
Early intervention is crucial to reduce excess weight and associated cardiometabolic risks in this underserved patient group.
Strengths and limitations
This is a strong study with a large sample size, using a solid methodology. The design choice of a cohort study enables a comparison to be made between those with SMI and those without a diagnosis, and the definition of the cohorts followed a logical process. This approach enables a number of potential limitations to be eliminated, as the cohorts are closely matched in demographic profile and socio-economic status. The possibility of different approaches being taken in different primary care practices, or of variations in practice over time, is also eliminated by the study design.
The use of existing primary care data ensures that there is no loss to follow up within the study, as no direct contact with participants was required. However, as with any study based on routinely collected data, there is the possibility that the quality and completeness of data varied between included practices.
It was not possible within this study to disaggregate data to analyse weight gain by different individual, or combinations of, antipsychotics prescribed. It may be that there is actually some variability, although further tailored research would be required to consider this fully.
The study design was influenced by a panel of twelve people with lived experience of SMI. The paper reports that their experiences were important in designing the study, although there is no mention of any input being sought into the analysis of its outcomes and its conclusions.
Cohorts were closely matched in demographic profile and socio-economic status.
Implications for practice
It is well established that people with SMI have a significant reduction in life expectancy – by as much as twenty to twenty five years (John et al, 2018, Public Health England, 2018). Higher rates of obesity and the resultant increased risk of cardiovascular and other diseases are known to be significant contributing factors to this mortality gap.
This paper demonstrates that the highest risk of weight gain occurs in the period immediately after diagnosis, and particularly in the early years of taking antipsychotic medication. The need for corresponding early intervention to control weight gain and reduce the associated physical health risks is therefore clear.
While the study shows that advice on weight management is often given to people diagnosed with a severe mental illness, rates of referral to weight management support services are very low. There is a clear missed opportunity here and people with severe mental illness should be referred for support immediately after diagnosis as a matter of routine.
Increased weight is often seen as inevitable for people with severe mental illness due to medication side effects and lifestyle issues, but this does not need to be the case. If the immediate risks are correctly identified and support is given, it could have a major impact on reducing weight gain – and therefore helping to close the alarming mortality gap.
People with severe mental illness should be referred to weight management services immediately after diagnosis as a matter of routine.
Statement of interests
Gordon Johnston is an independent peer researcher and has no conflicts of interests to declare.
Links
Primary paper
Charlotte L Lee, Min Gao, Margaret C Smith, Xue Dong, Felicity Waite, Prof Paul N Aveyard, Carmen Piernas (2025) Weight trajectories and access to weight management services in individuals with severe mental illness in the UK: a population-based, matched cohort study. The Lancet Psychiatry, Volume 12, Issue 10, 736 – 745
Other references
Firth, J et al. (2019) The Lancet Psychiatry Commission: a blueprint for protecting physical health in people with mental illness. The Lancet Psychiatry, Volume 6, Issue 8, 675 – 712
John A et al (2018). Premature mortality among people with severe mental illness. Schizophrenia Research. 199, 154-162
Public Health England. (2018). Severe mental illness (SMI) and physical health inequalities: briefing.
