Can Negative Mood Increase Inflammation? What Research Shows

By Grant Frost · Physiotherapist • Last clinically reviewed: 01 October 2026

We often talk about mental health and physical health as though they are two separate things.

But the relationship between our emotional state and what happens inside the body is considerably more complicated than that.

A fascinating 2018 study from researchers at Penn State University investigated whether people's everyday emotional experiences were associated with measurable markers of inflammation in their blood.

What makes this study particularly interesting is that the researchers didn't simply ask people how they had been feeling over the previous few weeks and then take a blood sample.

Instead, participants repeatedly reported their mood throughout the day for two weeks. This allowed the researchers to investigate whether when the mood was measured might be just as important as how much negative mood someone reported.

That distinction is important, because it changes how we might interpret the study.

What Did the Study Investigate?

The study, published in Brain, Behavior, and Immunity in 2018, investigated whether positive and negative emotional states were associated with markers of inflammation in adults living in the community.

The researchers were particularly interested in whether the way mood was measured affected the relationship they observed.

This is an important distinction because most studies asking about mood rely on people remembering how they have felt over a relatively long period.

Memory is useful, but it isn't perfect.

The researchers wanted to know whether repeatedly measuring people's emotions in real time might provide a different picture.

How Was the Study Conducted?

The study included 220 adults aged 25 to 65 from a community-based sample. Approximately 65% were women, 62% identified as Black/African American and 25% as Hispanic/Latino.

Participants first completed questionnaires that included measures of their recalled emotional state over the previous month.

They then completed ecological momentary assessments, or EMA, for 14 consecutive days.

In simple terms, this meant participants were prompted on a smartphone approximately five times per day to report how they were feeling.

This produced a much more detailed picture of their everyday emotional experiences than asking someone to remember how they had felt over the previous month.

After the 14-day monitoring period, the researchers collected blood samples to look at specific inflammatory chemicals.

They measured C-reactive protein (CRP) as well as seven cytokines:

• IL-1β
• IL-6
• TNF-α
• IL-8
• IL-4
• IL-10
• IFN-γ

The seven cytokines were combined into a composite measure of inflammatory activity. CRP was analysed separately.

The researchers also adjusted their analyses for several factors that could influence inflammation, including age, sex, BMI, education, number of chronic health conditions and statin use.

What Did the Researchers Find?

If you simply averaged all of the participants' negative mood measurements across the entire 14-day period, there was no statistically significant association with either the seven-cytokine inflammatory composite or CRP.

In other words, the study did not find that people who generally experienced more negative emotion across those two weeks simply had higher inflammation.

But the researchers then separated the two weeks.

They found that greater negative affect during the second week was associated with higher levels of the seven-cytokine inflammatory composite.

Importantly, however, this association was not statistically significant for CRP.

Negative mood during the first week was also not significantly associated with either inflammatory measure.

Why Might Timing Matter?

This is probably the most interesting part of the study.

The researchers compared mood measured during the first week with mood measured during the second week.

The second week's measurements occurred closer to the blood collection.

Negative affect during week two was associated with the cytokine composite, whereas negative affect during week one was not.

The researchers also explored whether the relationship became stronger when mood measurements were closer to the blood draw. Their analyses suggested a trend in that direction, although the day-by-day analyses did not produce statistically significant associations at each time point.

This raises an interesting possibility: the relationship between emotional state and inflammatory activity may be sensitive to timing.

But this is still a hypothesis rather than something this study established.

The study measured mood repeatedly and inflammation at the end of the monitoring period. It therefore cannot tell us whether a bout of negative mood directly increased inflammation, whether inflammation influenced mood, whether another factor influenced both, or whether several processes were occurring simultaneously.

What About Remembering How You Felt?

Another interesting finding came from comparing real-time mood measurements with participants' memories of their mood.

At the beginning of the study, participants were asked to recall their affect over the previous month.

Those who recalled negative mood scores were not significantly associated with either the cytokine composite or CRP.

This highlights an important methodological issue in research: different ways of measuring the same psychological experience can produce different relationships with biological measures.

Someone's answer to "How have you generally been feeling over the last month?" is not necessarily measuring the same thing as repeatedly asking "How are you feeling right now?" throughout everyday life.

The researchers therefore suggested that the timing and method of emotional assessment may be important when studying the relationship between affect and inflammation.

What Does This Actually Mean?

I think there is a useful lesson here, but it might be slightly different from the norm.

This study doesn't demonstrate that being angry, sad or stressed automatically causes inflammation.

It also doesn't show that changing your mood will reduce your inflammation.

What it does show is that recent negative emotional experiences were associated with one measure of inflammatory activity in this particular group of adults, while broader measures of mood were not.

That distinction might sound subtle, but it is important.

Inflammation is influenced by many factors, including health conditions, body composition, medications, infection, physical activity and other biological and behavioural factors.

Emotional state is potentially one part of that much larger picture.

And the fact that the researchers found a relationship with the cytokine composite but not CRP is another reason not to oversimplify the findings.

What Are the Limitations of the Study?

There are several reasons to interpret these findings cautiously.

• It was observational. The researchers measured naturally occurring mood and inflammatory markers. This means the study can identify associations but cannot establish cause and effect.
• Inflammation was measured once. Blood was collected after the 14-day EMA period, rather than repeatedly throughout the study.
• The significant finding was specific. It involved negative affect during week two and the seven-cytokine composite. It did not extend to CRP.
• Some analyses were exploratory. The authors themselves emphasised the need for further research into the timing of affect measurement and inflammation.
• The participants were a particular community sample. The study included 220 adults aged 25-65, with a relatively high average BMI and a diverse racial and socioeconomic background. We shouldn't automatically assume the findings apply identically to every population.
• The study does not establish a treatment. It did not test whether reducing negative mood lowers inflammation, nor did it test a particular psychological intervention.

My Clinical Perspective

As a physiotherapist, I spend a lot of time thinking about the interaction between the physical and psychological aspects of health.

People don't walk into a clinic as a collection of separate body parts. Pain, sleep, stress, activity, recovery, mood and physical capacity can all influence how someone experiences their health.

That's one reason I find this type of research so interesting.

But I also think it's important not to take a fascinating biological association and turn it into a simple clinical rule.

The study doesn't tell us that negative emotions are the cause of someone's pain or inflammation.

It doesn't tell us that reducing stress will automatically lower their inflammatory markers.

And it certainly doesn't mean that someone experiencing depression, anxiety, or chronic stress should feel responsible for their physical symptoms.

What I take from the research is something much more practical:

Looking after sleep, physical activity, social connection, stress and mental health is worthwhile regardless of whether it changes an individual inflammatory marker.

And research like this helps us understand why the relationship between the mind and body may be more dynamic than a single snapshot can reveal.

Want personalised guidance?

If you'd like help with any persistent musculoskeletal issue, you can book with Grant either in Port Macquarie or via an online telehealth consultation.

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