In a series of studies using electronic health records, we show that adults with infections ranging from urinary tract infections to sepsis are at higher risk of developing a mental health condition than adults without infection.

One in four adults will experience a mental health problem each year in England. The causes or triggers of mental health conditions are not fully understood. Some research suggests that infections may affect mental health. However, we do not know whether specific infections are linked to particular mental health conditions.

To investigate this question, we conducted studies comparing the risk of mental health conditions between people with and without infections. The infections were; skin/soft tissue infections, urinary tract infections, gastroenteritis, lower respiratory tract infections, sepsis, and meningitis/encephalitis, and the mental health conditions investigated were common mental health conditions (CMD), anxiety and/or depression, and severe mental illness (SMI), which is one of schizophrenia, bipolar disorder, other psychoses.

Using de-identified electronic health records of millions of people from the UK, we categorised individuals who had been to their GP with one of the six infections as “exposed”. For each exposed individual, up to five individuals of a same age, sex, and registered at the same GP practice, were selected to be their “unexposed” comparators. We then compared the risk of developing CMD or SMI between these two groups. 

Results showed that people with each of the six infections were more likely to, at a later date, go to their GP with a mental health condition than people without infection, even after accounting for differences in demographics, lifestyle, and other health conditions. The smallest increase in risk was seen among people with skin/soft tissue infections, a 16% increase in risk of SMI and a 29% increase in risk of CMD. People with sepsis had a higher risk of both outcomes than people without sepsis; 69% for SMI and 58% for CMD. Across all infections, the risk of each mental health outcome was highest in the first year after infection. For some of the infections, there was evidence that people who attended hospital, in addition to the GP, were at even higher risk of CMD and SMI. This may reflect more severe infections having a bigger impact on mental health; further research is needed.

In conclusion, our study findings suggest that the risk of mental health conditions is higher among adults with infections, compared with those without, especially for more severe infections. Providing prompt infection treatment, targeted mental health support, and offering relevant vaccinations, may limit mental health outcomes.

We have presented these results at the European Public Health Conference in Helsinki in November 2025 and papers with more details and results from the CMD and SMI studies have been published in peer-reviewed journals. Jaime Fanjul Iglesias, a Research Assistant in the Brain Health Group, has also been investigating self-harm and suicide following infections, results that will be shared upon publication. 

Mental health and dementia academics, students, NGO workers, and business leaders gathered at LSHTM in November for a very successful Networking event hosted by the Brain Health group.

The meeting was kicked off by Dr Mudiwa Muwanigwa from University College London/UK Dementia Research Institute presenting her work on relationships between brain proteins and genetics and how their interaction relates to dementia. Dr Mudiwa Muwanigwa also spoke enthusiastically of communicating research results to a range of audiences and the need for more dementia research involving Black participants, currently severely underrepresented. 

Next, Dr Fell gave an overview of the rich data resource that is Akrivia Health. He described how the dataset can be used to obtain more detailed information on mental health symptoms and prescriptions for millions of patients, using natural language processing to extract much more detailed information, e.g. from doctors' notes, than is typically available in electronic health records. One of their case studies included the prediction of Clozapine treatment resistance in patients with schizophrenia.

Thirdly, Dr Demnitz-King from Queen Mary’s University of London presented evaluation results from the APPLE-Tree study, a home-based intervention study supporting people at risk of dementia to make lifestyle changes, including improving physical activity, diet, and sleep through health coaching and digital tools. The study reported small cognitive improvements after two years and work is continuing to examine longer-term effects and dementia risk.

To finish off the talks, Dr Suffel and Dr Gore-Langton, the event co-organisers, presented an overview of the work being done by the Brain Health group at LSHTM to investigate a range of acute and common infections as risk factors for mental health outcomes. Triangulating results from Indian survey data, English general practice and hospital records, and genetic and serological data, the group are investigating this complex and potentially causal association.

After such a range of talks and excellent questions from the audience everyone was ready for some refreshments and so headed to the famous LSHTM Pumphandle bar for some drinks and pizza thanks to Alzheimer’s Research UK. It was a brilliant event which sparked much discussion between people working in different sectors and parts of the country. Discussions which we hope lead to meaningful collaborations. There was much enthusiasm for a follow up event - watch this space!

Applications are currently open for two Medical Research Council – London Intercollegiate Doctoral Training (MRC-LID) funded PhD opportunities within the Brain Health Group at LSHTM. You will be part of both the Brain Health Group and the Electronic Health Records Group at LSHTH investigating risk factors of dementia.

The first project aims to understand the interactions between of hypnotic drugs, including benzodiazepines and z-drugs, other medications and sleep on the risk of dementia. If you are interested in sleep and dementia and would like to learn about pharmacodepidemiology, causal inference, and how to use large electronic health record data sets, this project might be suitable for you.

Read more information on the 2026-27 Project (Suffel & Strongman & Warren-Gash).

The second project aims to understand possible associations between severe mental illness, such as schizophrenia and bipolar disorder, and risk of dementia. If you are interested in mental health and dementia and are keen to learn more about health data science and causal inference methods, this project may be suitable for you.

Read more information on the 2026-27 Project (Gore-Langton & Warren-Gash).

Please, contact Anne Suffel ([email protected]) and Georgia Gore-Langton ([email protected]) if you would like to discuss these projects and the application process.

By Blossom Okparocha

Being at LSHTM was a fun and excellent learning experience. I got everything you could ask for from an internship, from enjoying myself playing chess with different colleagues during the annual party to learning an entirely new coding language to lending a hand in a literature review screening process.

My main highlight was the project and dataset assigned to me by my supervisor (Charlotte Warren-Gash) and her team. I acquired excellent analytical and coding skills over the past two months while working on the dataset from the Mexican Health and Ageing Study (MHAS). I could remember dreading the idea of using RStudio like it was yesterday. I am now an emerging RStudio salesperson (not actually of course), pushing the program to SPSS, Python, and STATA users. Aside from cleaning data and forming visually appealing graphs, analysing and explaining data enlightened me on the importance of understanding the “why” over the “what”. Explaining data patterns teaches us how populations work and guides further research, a vital requirement in leading health progression and removing health disparities. I am happy I had the opportunity to present my project to over 20 people and answer questions, which made me further think about how to analyse the data better.

I thought the great start of the annual party and rewards day was a trap for the trials ahead. However, although the workload increased as the internship progressed, meeting new people and learning new things became my focus.

I am overly grateful for such a great experience and all the lessons learned, and I thank everyone who joined me in the journey. 

As the Brain Health Group at LSHTM we are supporting this year’s Brain Health Challenge and The World Brain Day 2025.

Neurological disorders are a leading cause of disability worldwide.

With increased awareness, we can take steps toward earlier detection, better outcomes, and improved brain health for every stage of life.

That’s why this year’s World Brain Day theme—Brain Health for All Ages—is so important.

Help us raise global awareness.

#WBD2025 #BrainHealthForAllAges

#BrainHealthChallenge2025

Louis recently presented the findings of a systematic review in a poster at the British Geriatrics Society Spring Meeting. The review investigated the evidence for whether a broad range of infections are associated with telomere length or telomere attrition in adults. Telomeres are protective caps at the ends of our DNA, and their shortening is considered a sign of biological ageing. After screening over 8,000 studies and including 63 that met inclusion criteria, we found consistent evidence that HIV infection was linked to shorter telomeres. Findings for other infections such as herpesviruses and COVID-19 were mixed. However, many of the included studies had methodological limitations, leading to a high risk of bias. These results are relevant to brain health because accelerated ageing could increase vulnerability to age-related conditions like dementia. Building on this, our future research will use electronic health records to investigate whether accelerated biological ageing may help to explain a potential link between infections and dementia risk, while addressing the methodological limitations identified in previous studies.

Georgia presented some of the Brain Health group’s research at the Society for Social Medicine & Population Health 68th Annual Scientific meeting in Glasgow. The study investigated the association between nine infections, ranging from common infections such at urinary tract infections and diarrhoea, to less common infections such as malaria and tuberculosis, and the risk of each of impaired cognition, depression, and frailty, among adults in India. Using the Longitudinal Aging Study in India (LASI) dataset, we found that people who reported having had at least one of the nine infections were at greater risk of depression and frailty than those not reporting an infection. Our results for impaired cognition were harder to interpret; we found that reporting an infection was associated with improved cognition when compared to those not reporting an infection. It seems plausible that people with impaired cognition under-report previous infections, leading to this counter-intuitive result. We stress the need for further studies using infection data confirmed either by a doctor or a laboratory test, rather than self-reported. We are hoping to publish the results of this study in a scientific journal soon. The conference was a great place to hear about research, in to brain health and other topics relevant to population health, and to engage in discussions around the strength and limitations of the methods used to answer public health research questions. 

This summer, I had the incredible opportunity to complete an 8-week health data science internship at the London School of Hygiene and Tropical Medicine (LSHTM) within the Faculty of Epidemiology and Public Health. As an undergraduate student in Neuroscience and Psychology, I initially thought my academic background might not align perfectly with health data science. However, through this experience, I have been fascinated by how a single dataset can be used to answer a myriad of questions which is something I previously explored within my research methods modules.

My project

During my time at LSHTM, I worked on a project examining the impact of indoor air pollution on cognitive function in older adults in India. The data came from Wave 1 of the Longitudinal Ageing Study in India (LASI). After identifying a research question, the next challenge was determining the most appropriate methods of analysis; This step-by-step process taught me how to approach a dataset logically, starting with exploration and ending with practical applications.

One of the most fascinating aspects of this project was uncovering trends even before formal analysis began. For example, when exploring the characteristics of our sample, we observed that as education levels increased, the proportion of individuals exposed to indoor air pollution decreased. Exploring these demographic characteristics not only guided our analytical approach but also helped us determine the relevance of our research question.

Regular meetings with my supervisors provided valuable insights into the collaborative nature of research and the importance of diverse perspectives. Their feedback challenged me to consider angles and ideas I had not initially thought of which enhanced my understanding of the research process.

By the end of the analysis, our results suggested that indoor air pollution had a protective effect on impaired cognition—a finding contrary to our expectations. Our findings highlighted the importance of critically evaluating how data is collected and analyzed, and approaching unexpected results with a healthy amount of skepticism.

Exploring career paths

Beyond my project, I had the privilege of meeting with various experts within the faculty and gaining valuable insights into what a career in epidemiology looks like. I also had the chance to attend meetings with the Brain Health Group, which was particularly exciting as a Neuroscience and Psychology student. Witnessing current brain health research in action deepened my appreciation for how interdisciplinary approaches are shaping the field. Initially, I viewed my studies in Neuroscience and Psychology as distinct from fields like public health and epidemiology. However, my time at LSHTM revealed how interconnected these disciplines are and how easily they can be combined.   

Furthermore, I have gained increased confidence in using tools like RStudio for data analysis; This skill is highly relevant across various careers in public health, and I believe this internship has broadened the range of opportunities available to me in the future.

Final reflections

I thoroughly enjoyed my time at LSHTM. As well as enhancing my technical skills, I now have a clearer vision of my own career trajectory. The analytical skills, particularly with RStudio, and insights I gained at LSHTM have inspired me to explore opportunities where I can apply health data science techniques to research questions in brain health.

I am incredibly grateful to my supervisor, Charlotte Warren-Gash, as well as Georgia Gore-Langton, Kwabena Asare, and Kate Mansfield for their support throughout this project. Their dedication and expertise made this experience invaluable. 

We presented some of our research at the Alzheimer’s Association International conference in Philadelphia. One of our studies investigated links between the skin condition psoriasis and risk of developing dementia. Using large health records data from a cohort of adults in England, we compared risks of dementia between people with and without psoriasis. We found that psoriasis was associated with an increased risk of all-cause dementia. The association was stronger for vascular dementia than for Alzheimer’s disease.  We also found stronger associations in severe psoriasis compared to mild to moderate psoriasis.

We know that infections can affect the health of older adults in the short-term. However, we don’t fully understand long-term effects of infections on the brain. We studied the health of nearly one million adults in England aged 65 years or more. Using data from anonymous health records, we controlled for differences in factors such as age, sex, smoking and physical health. In our study, infections were linked to an increase in dementia cases. The more severe the infection, the higher the chance of developing dementia. Raised dementia risk persisted for more than 9 years after infections. We now need to find out more about why this happens and who is most at risk. Importantly, can preventing and treating infections help to preserve brain health?

Read the Washington Post article.

See the published paper.