New study highlights the urgent need to reduce inflammation in overweight people with depression

New research from King’s College London has shown for the first time that overweight people with depression are 2.4 times more likely to have clinically elevated levels of inflammation.

Futhermore, overweight people with depression were estimated to have an extremely high clinical risk of developing other medical conditions, such as heart disease, diabetes, and metabolic disorders.

The study, published in Psychological Medicine today (Thursday 18 March), emphasised the importance of developing new medical interventions to reduce inflammation in clinically vulnerable patients with depression.

Major global health issues

Depression and obesity are both considered major global health issues. Currently, one in five people are estimated to experience depression in their lifetime. In parallel, 39% of adults are classified as overweight and 13% obese, with the rates of obesity having tripled since 1975.

Being overweight or obese are major risk factors for developing depression, while depressive symptoms increase the likelihood of weight gain over time. Emerging evidence suggests that inflammation might play a key role in the link between depression and weight gain. Excess weight gain promotes inflammation while studies also show that high inflammation can cause depressive symptoms to appear.

Researchers also found that overweight people with depression had significantly higher inflammation levels compared with BMI-matched overweight controls. This demonstrates that depression significantly aggravated inflammation, well beyond the expected effect of excess weight gain on inflammation.

Participants were recruited through the Wellcome Trust NIMA Consortium. The sample of 216 participants consisted of 69 overweight patients with depression; 35 overweight control patients; 55 healthy-weight patients with depression and 57 healthy-weight controls.

Anna McLaughlin, lead author and a NIHR Maudsley BRC PhD student at King’s College London, said: 

“This research is highly relevant now as prevalence of depression, obesity and chronic conditions have increased in every age group, on a global scale. Our findings support the growing evidence that developing medical treatments to reduce inflammation may prove crucial in reducing the health risks associated with depression and excess weight gain.”

The study used C-Reactive Protein (CRP) to measure inflammation as CRP is the most widely used routine marker of inflammation in medicine and psychiatry. Furthermore, the cut-off level for clinically elevated inflammation as CRP>3 mg/L is already widely used by clinicians to calculate the risk for developing cardiovascular disease and metabolic conditions. Therefore, the finding that overweight patients with depression have an increased risk of demonstrating CRP>3 mg/L can help researchers and clinicians in a wide range of medical fields.

Dr Valeria Mondelli, senior author of the paper and Clinical Reader in Psychoneuroimmunology at Institute of Psychiatry, Psychology & Neuroscience, King's College London, said: 

“Our research highlights inflammation as an important mechanism in the vicious cycle between depression and obesity and the potential for medical therapies that target inflammation to break this cycle and to prevent this vulnerable group of patients from developing additional comorbid conditions.”

This publication was funded by the Wellcome Trust, Medical Research Council and the NIHR Maudsley Biomedical Research Centre at South London and Maudsley NHS Foundation Trust and King’s College London.

The data was collected as part of a large multi-centre clinical study investigating biomarkers of depression (BIODEP), which involved collaboration between King’s College London, University of Cambridge, University of Oxford, University of Glasgow and University of Brighton.

Further reading

Paper reference: McLaughlin, A. P. et. al. (2021) “The influence of comorbid depression and overweight status on peripheral inflammation and cortisol levels”. Psychological Medicine.