Chronic inflammation, long recognised for its role in severe physical conditions like heart disease and cancer, may also significantly worsen the psychological consequences of poor sleep. A recent study conducted by UCLA Health reveals that older adults who have insomnia and are also exposed to inflammatory responses are three times more likely to develop symptoms of depression compared to those who sleep well. This finding highlights the interconnection between physical and mental health, particularly in ageing populations where sleep disturbances and inflammation are becoming increasingly common.
Published in JAMA Psychiatry, the UCLA study is the first of its kind to explore the biological mechanism linking inflammation, insomnia, and depression in older adults. As we age, our bodies become more susceptible to chronic inflammation due to a decline in cellular function and immune resilience. This inflammatory vulnerability is often worsened by factors such as chronic illness, pain, psychosocial stress, and unhealthy lifestyle habits. Simultaneously, major depression affects over 10% of Americans aged 60 and older each year, posing profound implications for cognitive function, physical ability, and overall life expectancy.
Although previous research has independently linked both insomnia and inflammation to heightened depression risk, no study until now has directly investigated whether older adults with insomnia are more emotionally susceptible to inflammation-induced mood changes. The UCLA research, led by psychiatrist Dr. Michael Irwin, sought to fill this gap by investigating whether insomnia acts as a sensitising factor that amplifies depressive symptoms in response to increased inflammation.
In a rigorously designed randomised controlled trial, the study enrolled 160 individuals aged 60 and above from Los Angeles. Among these, 53 participants were diagnosed with insomnia, while 107 were categorised as healthy sleepers. Participants were then randomly assigned to either receive an inflammatory stimulus or a placebo. Following this exposure, the researchers assessed changes in mood using the depression subscale of the Profiles of Mood States questionnaire and analysed blood samples to measure inflammatory cytokine levels and depressive symptom severity.
Results showed that the inflammatory challenge effectively increased both inflammation markers and depressive symptoms across the board. However, older adults with insomnia experienced a much more pronounced response: they exhibited a threefold increase in depressive mood compared to healthy sleepers. Moreover, these depressive symptoms persisted for six hours or more in the insomnia group, in contrast to the fleeting emotional responses seen in those without sleep issues. This suggests that insomnia may biologically prime individuals for prolonged emotional distress when faced with physical immune stressors.
Dr. Irwin, who heads UCLA Health’s Cousins Centre for Psychoneuroimmunology and is a member of the UCLA Jonsson Comprehensive Cancer Centre, emphasised the significance of these findings. “Insomnia not only robs older adults of rest but also primes their immune system to make them uniquely vulnerable to depression when faced with inflammation,” he said. He advocates for targeted interventions that address this specific inflammation-linked pathway to depression, which could improve not only mental health outcomes but also overall quality of life in ageing populations. Future research will be necessary to determine whether these results extend to younger individuals and to evaluate their applicability across racially and ethnically diverse populations, particularly those who are disproportionately affected by insomnia and depression.
More information: Michael Irwin et al, Inflammatory Exposure and Depression in Older Adults With Insomnia, JAMA Psychiatry. DOI: 10.1001/jamapsychiatry.2025.1327
Journal information: JAMA Psychiatry Provided by University of California – Los Angeles Health Sciences
