Inflammation and Mental Health: What We Know About Links to Depression and Anxiety

Do you experience persistent fatigue, loss of interest in everyday activities, poor sleep or unexplained anxiety? These symptoms can have many causes. Research is also exploring possible links between mental health and inflammatory processes; symptoms alone cannot establish their cause.

An observed association between inflammatory markers and mental health difficulties does not prove that inflammation caused depression or anxiety in a particular person. Findings vary between studies and are influenced by other factors.

It may be associated with changes in metabolism, blood vessels, the nervous system and other bodily processes.

Sleep, stress, physical illnesses, medication and other circumstances need to be considered when interpreting findings. A simple explanation such as “inflammation causes depression” does not reflect the complexity of the research.

Fibre and short-chain fatty acids

Some gut bacteria process fibre and produce short-chain fatty acids, such as butyrate. These metabolites are being intensively studied in relation to the intestinal lining and the regulation of immune processes.

Although much of the body’s serotonin is produced in the gut, this serotonin does not pass directly into the brain. The gut influences the brain mainly indirectly, through neural, metabolic and immune signals.

Assessing diet requires consideration of the overall eating pattern, quantities and individual needs. A single meal cannot establish inflammatory activity or the cause of mental health difficulties.

What can CRP not tell you?

CRP alone cannot tell you where inflammation originates or whether it is causing mental health difficulties. It may be elevated with infection, injury, obesity, autoimmune disease or after substantial physical exertion.

They are not routine tests used to diagnose depression or so-called “leaky gut”.

A varied diet can include minimally processed foods such as:

• vegetables and appropriate portions of fruit,
• legumes and other sources of fibre,
• fish and sources of omega-3 fatty acids,
• nuts, seeds and olive oil,
• eggs, meat or suitable plant-based sources of protein,
• fermented foods according to individual tolerance.

Consider limiting sugary drinks, sweets, frequent snacking on treats, fried foods and highly processed foods.

The small, 12-week SMILES trial involving 67 adults recorded an improvement in depressive symptoms in a group receiving professional dietary counselling compared with a social support group. Most participants also continued their treatment. This does not prove that a particular food or supplement treats depression, or that reduced inflammation caused the improvement.

Gut microorganisms use components of the diet, particularly different types of fibre. Examples of foods containing fibre include:

vegetables, legumes, onions, garlic, leeks, chicory, oats, nuts and seeds.

Food tolerance is individual. If digestive difficulties recur, discuss an appropriate eating pattern with a doctor or qualified nutrition professional. Findings from microbiome research cannot automatically be applied to the effects of probiotic supplements on depression or anxiety.

Physical activity can form part of mental health care. Choose a manageable activity suited to your circumstances and health, such as a short walk. Intensity should be individual; there is no requirement to achieve an athletic performance.

A regular sleep–wake routine is part of everyday care. Persistent insomnia or pronounced daytime sleepiness should be discussed with a doctor. Adjusting your routine does not guarantee reduced inflammation or recovery from mental health difficulties.

When difficulties persist, it makes sense to assess both physical and mental health. There is no need to assume in advance that inflammation is the cause. Investigations and any treatment are chosen according to the individual findings.

Do not start taking anti-inflammatory medicines or antibiotics for mental health difficulties without medical advice. Do not stop prescribed medicines, including antidepressants, without consulting your doctor.

If sadness, anxiety, apathy or loss of interest persists, interferes with everyday functioning, or thoughts of self-harm occur, seek professional help. In an immediate emergency in the EU, call 112.

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What should you remember?

The brain is not separate from the rest of the body. The gut, immune system, metabolism, sleep and mental processes interact with one another.

Research observes an association between inflammatory markers and mental health difficulties in some people. This association alone does not establish the cause in an individual.

Professional care is important for mental health difficulties; sleep, physical activity and diet can be part of that care. Any identified physical illnesses are assessed and treated separately.