Inflammation and Insomnia Together Spike Depression Risk in Seniors
Older adults with insomnia are more prone to depression when inflammation is present, UCLA study shows.
Older adults who suffer from insomnia may be more susceptible to depressive symptoms if they also experience elevated levels of inflammation, according to a randomized controlled trial published in JAMA Psychiatry. The research highlights a potential biological pathway linking poor sleep and mood disorders in later life.
Investigating the impact of inflammatory challenge
Researchers at the University of California Los Angeles (UCLA) examined 160 adults aged 60 years and older. Among these participants, 53 had insomnia, and 107 were considered healthy sleepers. Individuals from both groups were randomly assigned to receive either an inflammatory challenge or a placebo. This intervention was used to assess mood changes and inflammatory markers in the blood.
An inflammatory challenge involves exposing individuals to substances that temporarily increase inflammation, allowing researchers to observe biological and behavioral responses under controlled conditions.
Following the inflammatory challenge, individuals with insomnia showed a threefold greater increase in depressive symptoms than those without sleep issues. Depressive mood in participants with insomnia also persisted longer – typically six hours or more – compared to the transient mood shifts observed in the healthy sleeper group.
Understanding inflammation in the aging process
As people age, they face increased susceptibility to chronic inflammation, which may be driven by cellular aging, immune system decline and external factors such as stress or pain. Previous research has independently associated inflammation and insomnia with higher risk of depression. However, this study is the first to demonstrate that the combination of insomnia and induced inflammation may produce a synergistic effect on depressive mood in older adults.
The depressive symptoms observed in this study were measured using a validated mood assessment scale, and cytokine levels were used to quantify the inflammatory response. The researchers note that these findings may be particularly relevant given the prevalence of both insomnia and depression in older populations.
Cytokines
Cytokines are small proteins secreted by cells, particularly those in the immune system, that help regulate inflammation and immune responses.
Future research directions
The authors of the study emphasize the need to explore whether similar biological mechanisms operate in younger individuals with insomnia. They also suggest that future studies should examine whether the results are consistent across diverse racial and ethnic populations, who often face higher rates of sleep disturbance and mood disorders.
Reference: Irwin MR, Boyle CC, Cho JH, et al. Inflammatory exposure and depression in older adults with insomnia: a randomized clinical trial. JAMA Psychiatry. 2025. doi: 10.1001/jamapsychiatry.2025.1327
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