ME/CFS Is Not Static: What the Science Says About Timing and the Immune System
By Aimee Mills-Viscovich, LICSW
Please see the disclaimer at the end of the blog post.
Last reviewed: September 26, 2026
“Your labs are normal.” If you live with ME/CFS, or love someone who does, you’ve probably heard some version of that sentence more than once. Sometimes it comes with “there’s no clear marker for this” or “we’re not really sure what’s going on.” Hearing it again and again can leave you doubting what your own body is telling you.
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a long-term illness marked by post-exertional malaise: a worsening of symptoms after physical, mental, or emotional effort, often described as “crashing,” that can last for days. One reason the research on the ME/CFS immune system has been so confusing is that the illness may not look the same, biologically, at every stage. A 2015 study was one of the first to show that clearly.1
What did the 2015 study look at?
Researchers measured 51 immune signaling molecules, called cytokines, in the blood of 298 people with ME/CFS and 348 healthy people. Their key decision was to sort patients by how long they had been ill: three years or less, or more than three years. That one choice changed what the data showed.1
Cytokines are chemical messengers the immune system uses to coordinate its response, turning inflammation up or down. Earlier cytokine studies in ME/CFS had produced conflicting results, and the team wondered whether that was partly because those studies mixed together people at very different points in their illness.1
What happens to the immune system early in ME/CFS?
In the 52 people who had been ill for three years or less, many cytokines were higher than in healthy people. That included molecules that turn inflammation up and molecules that calm it down. The usual coordination between these signals also looked disrupted, as if the system were switched on but poorly regulated.1
One signal stood out: interferon-gamma, an immune messenger that has been linked to the fatigue that follows viral infections such as mononucleosis. It had the strongest association with the early stage of illness.1
What changes after three years?
In the 246 people who had been ill for more than three years, the early pattern was gone, and several of the same cytokines were actually lower than in healthy people. The researchers offered one possible explanation, a kind of “exhaustion” of the cells that make these signals, but they were clear that this was speculation.1
They also found that the immune differences tracked more closely with how long someone had been ill than with how severe their symptoms were. That’s what “not static” means here: the biology of ME/CFS may shift over time.1
Has this finding held up?
Partly. The broader idea that ME/CFS involves real immune changes has held up well. But I haven’t found a large study that has directly repeated the exact three-year comparison, and other research has pointed in somewhat different directions. That’s normal in a field that is still young.
In 2017, a Stanford team measured the same 51 cytokines in 192 people with ME/CFS, most of whom had been ill for more than 10 years. On average, only two cytokines differed from healthy people. But 17 of them, including interferon-gamma, rose steadily as symptoms became more severe.2 So while the 2015 study found that illness length mattered more than severity, the 2017 study found that severity mattered a great deal. The two studies grouped people differently, and both findings may be part of a bigger picture.
In 2024, an intensive National Institutes of Health study of people whose ME/CFS began after an infection found immune changes that the authors described as consistent with ongoing immune stimulation and possible immune exhaustion.3 That fits with the 2015 idea, though the NIH study didn’t test the three-year cutoff. (If you’ve ever wondered why so many tests come back “normal,” my post ME/CFS Biomarkers Explained goes into that.)
Why might interferon-gamma matter for brain fog and mood?
This part is theory, not something the 2015 study tested. In research on depression and other conditions, long-lasting inflammation can change how the body uses tryptophan, the building block of serotonin and melatonin. Some researchers think this may help explain brain fog, sleep problems, and mood changes in ME/CFS, but it hasn’t been confirmed.4,5
Here’s the proposed chain. Inflammatory signals such as interferon-gamma switch on what’s called the kynurenine pathway, which pulls tryptophan away from making serotonin and melatonin. One product of that pathway, quinolinic acid, can overstimulate glutamate receptors in the brain.4 Most of this evidence comes from studies of depression, not ME/CFS. A 2022 review argued that this pathway deserves serious study in ME/CFS, but it remains a well-reasoned hypothesis.5
What does this mean for care?
The 2015 study didn’t test any treatment, so it can’t tell anyone what to do. What it offers is a framework: someone early in ME/CFS and someone who has been ill for many years may not have the same biology, so it makes sense that one approach wouldn’t fit everyone.
That framework may help explain why study results have been so inconsistent, and why many people with ME/CFS find that well-meaning advice makes things worse. Many people I work with describe the same experience: “pushing through” didn’t build them back up. It knocked them down further.
Evidence-Based Treatment Recommendations
Each recommendation is labeled by the kind of evidence behind it. “Guideline-based” means it comes from a formal clinical guideline. “Extrapolated” means it’s my reading of where the research points, not something a study tested directly.
For you
Stay within your energy limits rather than pushing through symptoms. This approach is often called pacing. (Guideline-based: the UK’s 2021 NICE guideline advises people with ME/CFS to stay within their energy limits.6)
Be cautious with any program that increases activity on a fixed schedule, such as graded exercise therapy. (Guideline-based: NICE advises that these programs should not be offered for ME/CFS.6)
If you’re newly ill and your symptoms fit ME/CFS, ask about it early rather than waiting. (Extrapolated: the 2015 study suggests the early phase may be biologically different; it did not test early treatment.1)
Be wary of products that promise to “boost” or “calm” your immune system. Any medication or supplement aimed at the immune system is something to talk through with your prescriber. (Extrapolated: immune findings differ by stage and by study, so a one-direction approach may not fit.1,2)
For clinicians
Ask about illness onset and duration during assessment, and document them. (Extrapolated from the duration and severity findings.1,2)
Don’t recommend general exercise or fixed-increment activity programs. (Guideline-based.6)
Treat post-exertional malaise as a core feature, and plan session length and homework with energy limits in mind. (Guideline-based: NICE names post-exertional malaise as required for diagnosis.6)
Offer cognitive behavioral therapy as support for living with the illness, not as a cure. (Guideline-based.6)
When clients report low mood, poor sleep, or brain fog, consider that these may be part of the illness rather than a separate psychiatric problem. (Extrapolated, based on theory that hasn’t been confirmed in ME/CFS.4,5)
Honest caveats
The early-illness group in the 2015 study was small (52 people), and 51 different molecules were compared. With that many comparisons, some findings could be chance results.
The study compared different people at different stages. It didn’t follow the same people over time, so it can’t show that any one person’s immune system changes this way.
Illness length was based on when people reported their symptoms starting, which can be hard to pin down.
The kynurenine explanation for brain fog and mood is a theory drawn largely from depression research.
The NICE guideline is from the United Kingdom. It is one of the most detailed reviews of ME/CFS care, but guidelines elsewhere may differ.
If you’d like support
Many people I work with are autistic, and some describe living with both ME/CFS and autistic burnout, two different conditions that can be hard to tell apart from the inside. If that sounds familiar, you can learn more about our burnout group, a space to make sense of that exhaustion alongside others who understand it.
Notes
Hornig, M., Montoya, J. G., Klimas, N. G., Levine, S., Felsenstein, D., Bateman, L., Peterson, D. L., et al. (2015). Distinct plasma immune signatures in ME/CFS are present early in the course of illness. Science Advances, 1(1), e1400121. https://doi.org/10.1126/sciadv.1400121
Montoya, J. G., Holmes, T. H., Anderson, J. N., Maecker, H. T., Rosenberg-Hasson, Y., Valencia, I. J., Chu, L., Younger, J. W., Tato, C. M., & Davis, M. M. (2017). Cytokine signature associated with disease severity in chronic fatigue syndrome patients. Proceedings of the National Academy of Sciences, 114(34), E7150–E7158. https://doi.org/10.1073/pnas.1710519114
Walitt, B., Singh, K., LaMunion, S. R., Hallett, M., Jacobson, S., Chen, K., et al. (2024). Deep phenotyping of post-infectious myalgic encephalomyelitis/chronic fatigue syndrome. Nature Communications, 15, 907. https://doi.org/10.1038/s41467-024-45107-3
Miller, A. H., Haroon, E., Raison, C. L., & Felger, J. C. (2013). Cytokine targets in the brain: Impact on neurotransmitters and neurocircuits. Depression and Anxiety, 30(4), 297–306. https://doi.org/10.1002/da.22084
Kavyani, B., Lidbury, B. A., Schloeffel, R., Fisher, P. R., Missailidis, D., Annesley, S. J., Dehhaghi, M., Heng, B., & Guillemin, G. J. (2022). Could the kynurenine pathway be the key missing piece of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) complex puzzle? Cellular and Molecular Life Sciences, 79(8), 412. https://doi.org/10.1007/s00018-022-04380-5
National Institute for Health and Care Excellence. (2021). Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: Diagnosis and management (NICE Guideline NG206). https://www.nice.org.uk/guidance/ng206
🤖 AI DISCLOSURE: I used AI tools to help analyze and summarize the peer-reviewed research in this post. Every citation has been checked against the original source. Please refer to the original articles for complete findings.
📋 FOR INFORMATIONAL PURPOSES ONLY: This content is intended for general educational purposes. It does not constitute clinical advice, diagnosis, or treatment for any specific individual.
🩺 CONSULT A MEDICAL PROFESSIONAL: Any information related to health conditions, medications, or medical decisions should be discussed with a licensed physician or qualified healthcare provider.
🧠 CONSULT A MENTAL HEALTH PROFESSIONAL: Please consult a licensed mental health professional (LICSW, psychologist, psychiatrist, or LMFT) regarding concerns specific to your situation.