New Delhi: Older adults who struggle with insomnia may be three times more likely to develop depressive symptoms when their bodies mount an inflammatory response, according to a study published in JAMA Psychiatry.The clinical trial, which involved 160 participants with an average age of 66, found that exposed to an inflammatory challenge, those with insomnia experienced a threefold increase in depressed mood and symptoms compared to their well-rested peers. Their low mood also lingered for more than six hours while the effects were only temporary in those without insomnia.Dr Rajiv Mehta, senior consultant psychiatrist at Sir Ganga Ram Hospital, said the findings were highly relevant to clinical practice. “It’s often like a chicken-and-egg situation — does insomnia cause depression or is insomnia a symptom of depression? The two are closely linked,” he said. “Insomnia is usually part of the depressive spectrum and people with insomnia are much more vulnerable to negative thinking, which stresses the brain,” Dr Mehta explained. Stress on the brain, he added, can spill over to other body systems and make them vulnerable too.To test the connection, researchers administered a small dose of endotoxin to half the participants, which safely triggered temporary inflammation, while the rest received a placebo. Mood changes were then measured using self-reports and clinical assessments. Inflammation is the body’s natural defence against infection or injury, but when heightened, it can also disrupt brain chemistry and mood. Both groups showed similar biological signs of inflammation, including elevated cytokines, but only those with insomnia displayed a strong connection between this immune response and worsening mood.Explaining the science behind the finding, Dr Pavitra Shankar, associate consultant in psychiatry at Aakash Healthcare, said cytokines — signalling proteins of the immune system — can cross into the brain and disrupt the way nerve cells communicate. “During inflammation, especially in what we call a cytokine storm, levels of IL-6 and TNF-surge. They disturb the brain systems responsible for serotonin and dopamine, the chemicals that regulate mood. For older adults with insomnia, this disruption is amplified, worsening depression and impairing emotional regulation,” she said.The study’s authors concluded that older adults with insomnia carry a “hidden vulnerability” and should be closely monitored for depression during infections or illnesses, when inflammation is high.Dr Prashant Goyal, senior consultant in psychiatry at Sri Balaji Action Medical Institute, pointed to growing evidence for interventions that improve both sleep and inflammation. “Cognitive behavioural therapy for insomnia and mind-body practices like tai chi have been shown to improve sleep and reduce inflammatory markers. Exercise programmes, whether aerobic or resistance, also help lower inflammation and improve mood,” he said. “This trial strengthens the case for combining sleep therapies with physical activity and stress reduction to prevent depression.” With India’s ageing population set to double in the coming decades, experts warn that the overlap between insomnia, inflammation and depression will only grow in significance. Addressing sleep problems, they say, could be a key strategy in protecting their mental health.
