Rates of of depression, anxiety and suicide are at an all time high. While it might be easy to blame worldly events such as the pandemic and all its fall out, other causative theories are worth considering. Since naturopathic medicine aims to identify the cause of disease, taking a holistic approach to possible etiologies is important.

One theory, called the cytokine theory of depression, posits that depression may be linked to inflammation. While research into inflammation as a possible cause of mood disorders has been relatively minimal, a study published in the Journal of Abnormal Psychology last year found that inflammatory markers helped to predict a diagnosis of major depressive disorder (MDD) over a 9 year period. This association was seen most strongly in women and those who had life stressors. In other words, for those who are already vulnerable to low mood due to life circumstances, inflammatory markers can be predictive of their likelihood to develop MDD.

Inflammation is a normal biological response in certain situations such as injury or cell damage but if it does not resolve or is fueled by diet or lifestyle factors, then it can contribute to a broad range of pathologies such as cancer, arthritis, and even endocrine disorders. But looking at inflammation when treating mood disorders has not traditionally been done. And yet as we hear stories of hospitals overwhelmed by suicidal patients and depressed teens who cannot find mental health care providers with openings, it makes sense to start by looking at some of our most basic biology, our inflammatory pathways.

A simple blood test can easily look at inflammatory markers. When elevated, the more challenging task can be identifying the source of inflammation. One common cause is poor gut health. The link between gut and brain health has long been known but recent research has further elicited the mechanistic pathways. Since most of the body’s serotonin is made in the gut, a digestive tract with altered permeability (known as “leaky gut”) or a nutrient deficiency or inadequate diet can also clearly contribute to concerning mood symptoms.

Another possible cause of mood disorders are tick-borne illnesses. While Lyme disease is the most well known, there are many infections that can be caused by a tick bite and any infection can lead not only to inflammation but to psychiatric manifestations. Doctors are finding that some patients with refractory anxiety and depression have underlying infections. According to a quote, in the book “Chronic”, by Dr. Jill Buchwald, a New York based psychiatrist, “A ridiculous number of people with psychiatric illnesses actually don’t need psych meds. They need antibiotics.”

In an article published last year by Dr. Brian Fallon at Columbia University, they analyzed data from the Denmark National Patient Registered found that individuals with Lyme had high rates of mental disorders with especially high levels of suicide attempts and death by suicide. Their findings showed that these rates were highest six months to three years after a Lyme infection. When we consider that most of those infected with Lyme never see a tick bite and that our standard Lyme tests are unreliable, we must continue to consider tick-borne infections as a possible causative agent for psychiatric illnesses especially for those who are at high risk given their geographic location.

An infection causing psychiatric symptoms does not necessarily mean that the nervous system has been infected but can be a result of inflammatory markers impacting the brain and contributing to symptoms. So, in other words, the cause of anxiety or depression, can also be a combination of both of these theories; the cause can be both infectious and inflammatory.

Our current mental health crisis is calling our attention to the need to take a more holistic approach to the health of our nervous system. Our mood is influenced by our physiology. Given how our nervous system regulates our body, investigating the function of various systems (immune, gut, endocrine) in light of a mood disorder is imperative.


Zainal, N. H.; Newman, M. G. (2021). Increased inflammation predicts nine-year change in major depressive disorder diagnostic status. Journal of Abnormal Psychology. 13(8): 829-840.