No. According to MedlinePlus, the patient site of the National Library of Medicine, no lab test can diagnose depression. In 2026, experts from several countries said the proposed inflammatory type has no agreed definition or test tools. So no blood test confirms it as of September 2026. A 2026 umbrella review from King’s College London also found that the evidence does not yet support using inflammation markers to guide treatment.
I am a psychiatrist and the founder of Washington Behavioral Medicine Associates. Perhaps you have tried two or more antidepressants, and a clinic has offered you a CRP, cytokine or neuroinflammation panel. This page lays out what research on inflammation and depression says those tests can show, so you know what a result could change before you pay.
Blood Tests, Inflammation and Depression
Can a Blood Test Diagnose Depression?
MedlinePlus says no blood test for depression can diagnose it. Blood tests still have a place in the workup. A provider may order them, MedlinePlus explains, to see whether a condition such as anemia or thyroid disease may be causing the symptoms. Screening for depression itself works through questions about your feelings, thoughts and behaviors.
The National Institute of Mental Health (NIMH) describes the same logic. Certain medicines and medical conditions, such as viruses or thyroid disorders, can cause the same symptoms as depression. A provider can rule them out with a physical exam, an interview and lab tests. In a depression evaluation, blood work looks for another cause. It does not confirm the depression.
At Washington Behavioral Medicine Associates, our testing services follow the same approach. When relevant, we may run lab tests such as complete blood counts and screenings for liver, kidney and thyroid function. In some cases, we also test for infectious conditions, including Lyme disease and streptococcus (PANDAS).
How Researchers Connect Inflammation and Depression
Inflammatory depression is a research idea. Today’s diagnostic manual does not include it. In studies of inflammation and depression, one blood marker is C-reactive protein, or CRP. Doctors use it to measure inflammation throughout the body. Emory researchers note that studies keep finding CRP raised in a subset of people with major depression, which raises the question of how large that subset is.
One estimate comes from a 2019 meta-analysis in Psychological Medicine. Pooling 30 studies, it found low-grade inflammation, meaning CRP above 3 mg/L, in 27% of people with depression. CRP above 1 mg/L appeared in 58%. Against matched healthy controls, people with depression had 1.46 times the odds of low-grade inflammation. The review drew on 37 studies in all.
The link between inflammation and depression also seems to follow certain symptoms. A 2021 analysis in the American Journal of Psychiatry pooled 15 population-based cohorts and 56,351 adults. It linked higher CRP with appetite changes, low energy, sleep problems, feeling that everything was an effort and little interest in things. For four purely emotional symptoms, such as hopelessness and feeling fearful, the evidence was strongly against a link.
An expert panel went further in 2026. The ASPIRE group proposed ten symptom types for inflammatory depression. Among them are fatigue, oversleeping, lack of motivation, loss of pleasure, also called anhedonia, and slowed movement. It remains an expert proposal that has yet to be validated. A 2025 opinion piece in JAMA Psychiatry asked whether inflammation markers should join the next edition of the manual, the DSM-6.
How to Test for Inflammation and What CRP or hs-CRP Can and Cannot Show
A CRP test measures C-reactive protein in a blood sample. Your liver makes CRP in response to inflammation, the body’s way of protecting tissue and helping it heal from injury, infection or other disease. The MedlinePlus guide to the CRP test says the result tells you how much inflammation you have. It does not tell you what is causing it or where it is.
An hs-CRP test is the high-sensitivity version. It picks up very small rises in CRP, and MedlinePlus gives its use as estimating the risk of heart disease. The table below lists the tests you may be offered for inflammation and depression and what each can and cannot show.
How to Test for Brain Inflammation Is Still a Research Question
So far, research has measured blood far more than the brain. A 2019 review of 69 studies on inflammation and depression saw raised blood markers again and again. Only a few studies had looked at the brain, using spinal fluid, PET scans and post-mortem tissue. Spinal fluid and PET markers did not track blood markers.
A single later study pointed the other way. In unmedicated adults with depression, Emory researchers found blood CRP strongly correlated with CRP in spinal fluid. Their measure required a spinal tap. A blood CRP result is therefore not a direct reading of brain inflammation, though one study suggests the two may move together.
Can an Inflammation Test Guide Your Depression Treatment?
This is the question that matters most if you are paying for a panel, and it is the one the 2026 umbrella review from King’s College London took on. The team found eight meta-analyses on inflammatory markers and treatment response in major depression. They covered antidepressants and electroconvulsive therapy (ECT). The studies inside them overlapped heavily, so the eight are not eight separate bodies of evidence.
For antidepressants, some meta-analyses linked lower starting CRP, or falling markers during treatment, with better response. The findings were inconsistent and the effects generally small. For ECT, one meta-analysis found links that were significant only before correction for multiple testing, and none survived it. The authors concluded that the evidence does not yet support using inflammatory biomarkers to guide treatment decisions.
A 2026 meta-analysis pooled 11 randomized trials of prescription anti-inflammatory drugs. All enrolled people with depression and CRP of at least 2 mg/L. The drugs eased loss of pleasure and depression symptoms more than placebo, with small to moderate effects. Response and remission rates did not differ. The authors say such treatments may help people with heightened inflammation. Whether they fit your care is a question for a consultation.
A 2026 trial of tocilizumab, a drug that blocks the immune signal IL-6, shows how early the treatment side of inflammation and depression is. Its 30 participants had depression that had not responded well to antidepressants, plus low-grade inflammation. Each got one infusion or placebo. No result reached statistical significance, and its authors call for a large-scale efficacy trial.
Isn’t a Blood Test Better Than Guessing?
If you have been through two or three medicines, the frustration is fair. NIMH says finding the best treatment may take trial and error, and a lab number for inflammatory depression can feel like a way out. Yet a number helps only when it changes what happens next. A 2023 consensus review in World Psychiatry notes that very few factors of any kind are regarded as predicting non-response across treatments.
Broad panels bring a second problem. A 2026 Swedish study gave 56 lab tests to children with PANS, a neuropsychiatric syndrome, as PANS guidelines advise. Because it studied children with a different syndrome, it serves only as a comparison for adults with depression. At least one result came back abnormal in 86.3% of the PANS group and 96.6% of a comparison group with OCD or tic disorders.
Incidental findings that led nowhere were frequent, and the authors questioned the value of such costly workups. A 2025 review in the Journal of Clinical Investigation warns about antibody testing in psychiatric patients. Interest in autoimmune brain disorders, like the one in our guide to how autoimmune encephalitis is diagnosed, has driven testing that often neglects pretest probability. The term means how likely a condition was before anyone drew blood.
My own research has asked whether immune-related genes shape treatment response. In 2012, three colleagues and I published research on 1,953 participants in the Sequenced Treatment Alternatives to Relieve Depression study (STAR*D). It tested whether IDO, an enzyme that immune activation can raise, plays a role in response to citalopram. We called the results modest and in need of replication. These questions may help before you pay.
What to Look at When Depression Has Not Lifted
NIMH describes treatment-resistant depression as not getting better after trying at least two antidepressants. The World Psychiatry review says the FDA and European Medicines Agency adopted the most used definition, counting only adequate trials taken as prescribed. It estimates that at least 30% of people with depression meet it. It also finds that a significant share of them turns out to be pseudo-resistant, for example because earlier trials fell short.
Psychiatrists are medical doctors who specialize in mental health and can prescribe medicine, so a consultation can review that history in full. Our page on treatment-resistant depression and its treatment options covers what may come next. Some patients also ask about pharmacogenetic testing, which looks at how genes affect the way the body handles certain medicines.
The test neither measures inflammation nor diagnoses depression, and not every patient needs it or benefits from it. We offer it only to select patients. Our article on how genetic testing may help guide medication selection explains who may benefit from that metabolic information.
Frequently Asked Questions
How do doctors confirm depression?
Through an evaluation, not a lab result. NIMH says a diagnosis requires symptoms most of the day, nearly every day, for at least 2 weeks. One of them must be depressed mood or loss of interest. A provider asks about your feelings, thoughts and behaviors and may order blood work to rule out other causes.
Can inflammation in the body cause depression?
Studies link inflammation and depression, but cause is not settled. A 2016 review in Nature Reviews Immunology holds that links between inflammation and the brain appear to drive depression. One proposed route runs through IDO, which sends more tryptophan down the kynurenine pathway and leaves less for making serotonin. A 2018 meta-analysis found the links to each kynurenine product remain uncertain.
Do antidepressants reduce inflammation?
Studies find they lower some markers. A 2018 meta-analysis pooled 45 studies with 1,517 people. It found that antidepressants lowered several blood signs of inflammation. It found no evidence that the drop tracked whether patients got better, though few studies reported responders separately. Questions about your own medicines, or about inflammation and depression in your case, belong in a consultation.
Can inflammation cause anxiety?
Research hints at a link, but it is early. A 2019 meta-analysis of 14 studies in BMJ Open found CRP higher in people with generalized anxiety disorder than in controls. The effect was small and the studies varied widely. Its authors call the evidence preliminary. They say it is still unclear whether inflammatory cytokines, a type of immune signal, help cause the disorder.
Is the gut-brain axis linked to depression?
Gut bacteria show a pattern tied to both inflammation and depression, though not one unique to depression. A 2021 JAMA Psychiatry review looked at 59 case-control studies. It found fewer bacteria that calm inflammation and more that promote it in depression, bipolar disorder, schizophrenia and anxiety. Gut bacteria patterns have been proposed as biomarkers, and none is a validated depression test.
Can a high CRP result mean something other than depression?
Yes. MedlinePlus lists insomnia, depression, hormone therapy for menopause and obesity among things linked with raised CRP. It adds that females often have slightly higher levels. Injury, infection and other disease also trigger the inflammation CRP measures. Doctors read a CRP result alongside other tests, your symptoms and your health history before drawing any conclusion.
Do inflammation markers predict who will develop depression?
At the population level, possibly. A Swedish study followed 585,279 people with no psychiatric diagnosis. CRP above the median was linked to a 2% higher risk of any later psychiatric disorder. White blood cells, haptoglobin and IgG differed up to 30 years before diagnosis. The authors suggest these markers might help identify high-risk groups, but the finding cannot be read from one person’s result.
Talk Through Testing With a Psychiatrist
A clinic may have offered you a panel, or you may have questions about inflammation and depression. You can bring both to a psychiatric consultation before you pay. We can go over your treatment history, which tests are relevant to you and what each result would change.
Start care with our practice when you are ready.
This information is for educational purposes and should not replace a professional consultation. Schedule a consultation to discuss whether this approach may be right for you or your family.
