Pioneering link between census data and electronic mental health records

King's College London researchers are the first research team in England to link electronic mental healthcare records to census data, at an individual level, using the Clinical Record Interactive Search (CRIS) system.

Published in the ‘BMJ Open’ and funded by the NIHR Maudsley BRC and the Economic and Social Research Council (ESRC) the study involved linking de-identified data (with personal information removed) of 459,374 patients from South London and Maudsley NHS Foundation Trust to census data from 2011.

Researchers linked just over half (50.4 per cent) of the records and found that certain groups – young people between 25 and 34, and those from deprived areas and minority ethnic groups – were less likely to be matched to a census record.

Dr Jayati Das-Munshi, Clinical Reader in Social and Psychiatric Epidemiology at Institute of Psychiatry, Psychology & Neuroscience (IoPPN), King’s College London, said:

"This is the first time that large-scale routine mental health records have been successfully linked to individual socio-demographic data from the census in England and we achieved successful linkage for over half the records. The lower census response rate in those with severe mental illness is a potential concern, as the information is vital for service planning and the allocation of resources."

The likelihood of matching records across the two sets of data varied with the type of mental health condition. There were lower rates of success in those with schizophrenia or with mental disorders due to substance use. The rate of successful pairing was higher in those with mental disorders caused by brain injury or disease, as did those with frequent contact with services.

The aim of the study was to address the absence of socio-economic data in electronic healthcare records so the social factors of severe mental illness could be examined. The study used the Clinical Research Interactive Search (CRIS) system to extract de-identified records from South London and Maudsley NHS Foundation Trust and gauged the effect of potential biases caused by non-matched records.

Dr Das-Munshi added “In this study, we developed statistical methods, which will help us to minimise the impact of missing census data on future work. This new linked dataset will allow us to understand how social experiences impact the onset and outcomes of mental health conditions, at a scale which has never previously been possible in England.”

Lay summary by SEP-MD Service User and Carer Advisory Group

What is this study about?

The paper discusses connecting mental healthcare records from the South London and Maudsley Mental Health Trust with data from the 2011 census of England and Wales to add information about people's social and economic circumstances to their mental health data, to better understand how social and economic circumstances may affect mental health.

How did we link the records?

We used careful methods to match the electronic health records to people's census records to ensure accurate linkage of records. The linking process took place in a secure environment to protect people's anonymity. After the records were matched, details that might identify the individuals in the data, such as names, were automatically removed before researchers could access the data.

How secure is the data?

The data is processed according to strict guidelines from the Office for National Statistics. The linked data can only be accessed in named, secure locations by researchers and analysts who have been approved to view the data. All access to the data is fully-tracked and can be immediately reviewed in the case of a data breach. Any outputs, like tables of results or graphs, are independently checked by the Office for National Statistics to ensure no individual can be identified.

What did we find?

About half of the records could be linked and connected correctly, with the data of people from certain groups being harder to match and connect, for instance, those of young adults, those in deprived areas, and people belonging to some minority ethnic groups.

This finding raises a concern that people with some mental health conditions might have not been included in the 2011 census and that, as a result, their data was omitted and couldn't be connected, leading to gaps in future research, or an incomplete picture to inform service provision.

The study's strengths include the size and diversity of the data. It is now possible to demonstrate the effects of social and economic factors on people's mental health.

'Improving our understanding of the social determinants of mental health: A data linkage study of mental health records and the 2011 UK census' by Cybulski, L. et al (2024) was published in BMJ Open. doi:10.1136/bmjopen-2023-073582 

This study is an output of the Social and Economic Predictors of the Severe Mental Disorders: The SEP-MD Data Linkage Study

It was funded by the ESRC and supported by ADR UK (Administrative Data Research UK), the ESRC Centre for Society and Mental Health and the National Institute for Health and Care Research (NIHR) Maudsley Biomedical Research Centre.