Nobody likes the feeling of being in a negative emotional state, but those moody blues could represent something much more serious in terms of your overall health, new research suggests.
In a new study, researchers found that people's negative moods recorded throughout the day were associated with higher levels of inflammation – the body's natural immune response to injury and infection, but which is also a common hallmark of ill health and chronic disease.
Before now, most research investigating the links between negative affect and markers of inflammation have focussed on 'recalled affect', where study participants retrospectively report on their moods over the past week or month with a standard questionnaire.
To see whether a more regular kind of measurement called ecological momentary affect might provide a more refined assessment of mood, researchers from Pennsylvania State University dialled up the frequency.
"Many nuances with regard to how affect and inflammation are related remain unexplored," the authors, led by first author and biobehavioural health researcher Jennifer Graham-Engeland, explain in their paper.
"To our knowledge, no one has examined the degree to which assessment methods or timing modify the association between affect and inflammation."
According to the researchers, recalled measures of affect once time has passed are susceptible to memory bias and can be influenced by personality factors, whereas more of-the-minute, real-time momentary assessments are thought to offer a better way of capturing affective experiences.
With that in mind, Graham-Engeland and her team had the 220 participants in their sample – recruited as part of the larger Effects of Stress on Cognitive Ageing, Physiology, and Emotion (ESCAPE) study in the Bronx – rate their mood five times daily over the course of two weeks.
Prompted by smartphones, each of the participants would rate the extent to which they felt positive affect items (such as happy, pleased, enjoyment/fun, joyful) or negative affect (tense/anxious, angry/hostile, depressed/blue, frustrated, unhappy).
In addition to these multiple daily self-assessments, participants also had to report their recalled positive and negative affect at the end of the experiment.
During the study, they also had their blood drawn at the close of the experiment, to determine levels of inflammatory cytokines in their blood plasma.
When analysing the entire two-week trial, the researchers ultimately found no association between either recalled or momentary measures of negative/positive affect and inflammation markers.
But when they only analysed the last week of the experiment, there was an association with negative affect (NA), which the researchers attribute to the "temporal proximity" of the blood being drawn (at the end of the study).
"Whereas aggregated momentary NA from week 1 was not associated with any biomarker, aggregated momentary NA from week 2 was significantly associated with higher levels of the 7-cytokine composite measure of inflammation, controlling for age, gender, BMI, education, health conditions, and statin use," the authors write.
"To our knowledge these are the first analyses to show significant associations between aggregated momentary NA from daily life and subsequently assessed peripheral inflammation."
In other words, there seems to be at least some relationship between people's daily negative moods and inflammation markers that can be indicative of poor health and disease, although there's still a lot left to learn about what's going on here.
In addition, our extent to accurately measure this link is clearly still very much a work in progress – but the researchers say the new leads here could point to important findings in future study.
"We hope that this research will prompt investigators to include momentary measures of stress and affect in research examining inflammation, to replicate the current findings and help characterise the mechanisms underlying associations between affect and inflammation," says Graham-Engeland.
"Because affect is modifiable, we are excited about these findings and hope that they will spur additional research to understand the connection between affect and inflammation, which in turn may promote novel psychosocial interventions that promote health broadly and help break a cycle that can lead to chronic inflammation, disability, and disease."
The findings are reported in Brain, Behavior, and Immunity.