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A study in Japan found that the associations between inflammation markers and psychological symptoms such as depression, anxiety, fatigue, and somatic complaints are stronger in individuals with poor emotion regulation or low-quality sleep. On the other hand, these associations were attenuated or even reversed in individuals with effective emotion regulation or high-quality sleep. The paper was published in Brain, Behavior, & Immunity – Health.
Inflammation is a biological response of the immune system to injury, infection, or other forms of threat to the body. It involves the activation of immune cells and the release of signaling molecules such as cytokines that help eliminate harmful agents and initiate tissue repair. Acute inflammation is usually short-term and adaptive, supporting healing and recovery. Chronic inflammation, however, persists over time and can become harmful, contributing to a wide range of physical and mental health problems.
Inflammation can also be local or systemic. Local inflammation occurs in a specific tissue or area of the body in response to injury, infection, or irritation. Systemic inflammation, on the other hand, refers to inflammation that is spread throughout the body, reflected in elevated circulating inflammatory markers (such as C-reactive protein or cytokines in the blood).
In recent research, systemic inflammation has been increasingly linked to psychophysiological states such as fatigue, depression, anxiety, and somatic complaints. Elevated inflammatory markers tend to be associated with persistent tiredness and reduced energy, even in the absence of clear physical illness.
Inflammation can also influence brain function by altering neurotransmitter systems and neural circuits involved in mood regulation. This helps explain why chronic, systemic inflammation is linked to depressive symptoms such as low mood, anhedonia, and cognitive slowing.
Anxiety has likewise been associated with inflammatory processes, possibly through heightened stress reactivity and altered immune signaling. Somatic complaints, including pain, gastrointestinal discomfort, and bodily tension, are common in states of chronic inflammation.
Study author Kao Yamaoka and their colleagues wanted to explore the relationship between systemic inflammation and psychophysiological states, including symptoms of depression and anxiety. They note that elevated inflammatory markers are generally associated with worsened psychological outcomes, but that this is not the case in all individuals.
They hypothesized that emotion regulation, interoception (the ability to perceive sensations from the body), and sleep moderate this relationship. They expected individuals with greater interoceptive sensitivity, stronger emotion regulation abilities, and better sleep quality to be more resilient to the detrimental psychological effects of increased inflammation.
Study participants were 155 healthy adults between 30 and 59 years of age. They were required to have a body mass index of between 18.5 and 30.0 kg/m 2 and to have graduated from high school. Candidates were excluded if they had a current or past diagnosis of dementia, depression, or other psychiatric disorders, if they were pregnant or breastfeeding, if they were smokers, or could not discontinue medications or health supplements that could influence study outcomes.
Study participants completed assessments of emotion regulation skills (multiple assessments), sleep quality (the Pittsburgh Sleep Quality Index), interoceptive sensitivity (the Multidimensional Assessment of Interoceptive Awareness), maladaptive interoceptive processing (the Somatosensory Amplification Scale), fatigue (the Cumulative Fatigue Symptoms Index), depressive symptoms (the Beck Depression Inventory – II), mood (the Profile of Mood States 2-A Short Form), anxiety symptoms (the State-Trait Anxiety Inventory), and multiple assessments of stress responses.
Participants also completed a questionnaire assessing gastrointestinal symptoms and gave blood samples, allowing researchers to assess the levels of inflammatory markers.
Results showed that the associations between inflammatory markers and symptoms such as fatigue, somatic complaints, depression, and anxiety were stronger in individuals with poor emotion regulation or low-quality sleep. Conversely, in individuals with effective emotion regulation or high-quality sleep, this association was attenuated or even reversed. The moderating effects of interoceptive awareness were weaker or depended on the context.
“This study demonstrated that individual differences in emotion regulation, sleep, and interoception significantly influenced the relationship between inflammation and subjective mental and physical well-being. In particular, individuals with poor emotional regulation or low sleep quality were more vulnerable to the negative effects of elevated inflammatory markers, such as CRP, IL-6, and TNF-α, associated with greater fatigue, somatic complaints, depression, and anxiety.”
“Conversely, when emotion regulation and sleep were adequate, these associations were diminished or, in some cases, even reversed, which suggested that inflammation did not uniformly lead to adverse health outcomes; rather, it interacted dynamically with personal traits,” study authors concluded.
The study contributes to the scientific understanding of the links between inflammation and psychological states. However, it should be noted that the study was conducted on a relatively small sample. Also, the design of the study does not allow any definitive causal inferences to be derived from the results.
The paper, “Moderating Effects of Individual Factors on the Relationship Between Inflammation and Psychophysiological States in Healthy Adults,” was authored by Kao Yamaoka, Yuri Ishii, and Yuri Terasawa.
