A Functional Medicine Approach to Anxiety, Depression & Related Mood Disorders
Part of the Brain Health guide
Mental illness and brain-based disorders have become increasingly common in the modern world, and periods of heightened stress and isolation only make robust mental health harder to maintain. According to the National Alliance on Mental Illness, one in five American adults currently experiences mental illness, and 17 percent of U.S. adolescents have a mental illness. [1]
Before getting into the functional medicine approach to mood and brain-based disorders, let’s briefly cover some of the most common mental illnesses.
Common mental health disorders
Depression
More than 19 million U.S. adults, about 8 percent of the population, have experienced a depressive episode in the past year, making depression one of the most common mental illnesses. Symptoms vary from person to person but most commonly include:
- Changes in sleep habits
- Changes in appetite
- Lack of energy
- Lack of interest in activities
- Hopelessness or guilty thoughts
- Physical aches and pains
Left unaddressed, depression significantly impacts physical health, functioning, and relationships, and it tends to recur. Women are twice as likely as men to experience major depression, and also experience forms tied to fertility hormones, including premenstrual dysphoric disorder, postpartum depression, and postmenopausal depression. [2]
The conventional treatment for depression is a class of drugs called selective serotonin reuptake inhibitors (SSRIs). Yet research shows the clinical response is modest, with only 40 to 60 percent of people experiencing symptom relief and just 30 to 45 percent reaching remission. [3] SSRIs and other antidepressants also carry side effects that can themselves contribute to low mood, including weight gain, sexual dysfunction, depletion of beneficial gut bacteria, and withdrawal on discontinuation. [4] Notably, 25 percent of people on SSRIs have taken them for over a decade, yet no SSRI safety study has lasted more than two years. [5]
Anxiety
Anxiety disorders are the most common mental illness in the U.S., affecting more than 40 million adults. People with an anxiety disorder are three to five times more likely to see a doctor and six times more likely to be hospitalized for psychiatric disorders. [6] Most people diagnosed are prescribed SSRIs or benzodiazepines, the latter carrying their own side effects, including cognitive and sexual dysfunction and, paradoxically, increased anxiety and depression. [7]
Bipolar disorder
Bipolar disorder, once called manic-depressive disorder, is marked by dramatic swings in mood, energy, and activity. An estimated 2.8 percent of American adults experienced it in the past year, and 89 percent of people with bipolar disorder are seriously impaired. [8]
Post-traumatic stress disorder
PTSD affects people from all walks of life and generally results from acute trauma, such as combat, assault, disaster, or a severe accident. Complex PTSD results from repetitive and prolonged trauma, including ongoing abuse, neglect, and domestic violence. [9]
Eating disorders
Eating disorders encompass a range of food and body-image conditions, including anorexia nervosa, atypical anorexia, bulimia, binge eating disorder, purging disorder, and night eating syndrome.
Two theories of mental illness
When we ask why mental health issues occur, two leading theories stand out: the evolutionary mismatch theory and the pathogen-host theory.
Mental illness as an evolutionary mismatch. Mental illness is not inevitable; like many chronic conditions, it can be viewed as a disease of civilization, driven by a high-stress, industrialized lifestyle that is out of step with our genetics. Our bodies expect certain dietary and lifestyle inputs, and when those inputs are missing, we respond with dysfunctional outputs. Depression as a disease of modern life reflects our increasingly overfed, malnourished, sedentary, sunlight-deficient, sleep-deprived, and socially isolated way of living. [10]
Mental illness as a byproduct of infection and inflammation. A second theory frames inflammation as a driver of depression. [11] When our ancestors developed an acute infection, the inflammatory response produced low mood that slowed them down for recovery. As civilization and our immune systems changed, that once-adaptive mechanism became chronic, and so did the mental illness that came with it.
Underlying causes of anxiety, depression, and mood disorders
Taking both theories together, we can build a hierarchy of underlying causes. The major ones include:
- Infection and immune dysregulation
- The standard American diet
- Blood sugar dysregulation
- A sedentary lifestyle
- Impaired neurogenesis
- Gut-brain communication
- Circadian rhythm disruption
- Trauma
- Loneliness
- Environmental triggers
Infection and immune dysregulation. Many people carry chronic, low-grade stealth infections, viral, bacterial, fungal, or parasitic, that drive chronic inflammation with neurotoxic and neuroinflammatory effects. [12] A number of infections have been directly connected to mental disorders, including Lyme disease, streptococcus, and viral and parasitic infections. Microorganisms can significantly affect our brains and our behavior.
The standard American diet. One of the worst dietary templates in the modern world, it has been linked to poor health for years. Ultra-processed foods are associated with depression, and high refined carbohydrate intake induces neuroinflammation and anxiety-like behavior in animal models. [13]
Blood sugar dysregulation. More than 100 million U.S. adults live with diabetes or prediabetes, and blood sugar dysregulation is linked to depression and bipolar disorder. [14] Insulin does not just regulate blood sugar, it influences neuronal circuits and synaptic transmission, so imbalanced blood sugar drags on mood.
A sedentary lifestyle. Consistent physical activity is tied to good health, and a large body of research links sedentary living to anxiety and depression at every age. [15]
Impaired neurogenesis. Neurogenesis is how neurons grow and develop, and impaired neurogenesis appears to be a foundational problem in mental illness. [16] Influences include HPA dysfunction, low BDNF, chronic inflammation, microbiome changes, and traumatic brain injury.
Gut-brain communication. The gut-brain axis is a two-way pathway between the digestive nervous system and the central nervous system, and essentially every psychiatric or psychological function can be influenced by it. [17] Several gut bacteria produce neurotransmitters that shape how we feel, so a disrupted microbiome lowers those feel-good compounds and raises the risk of infection and inflammation.
Circadian rhythm disruption. Our biological clocks strongly influence mental and behavioral health. Modern life, too little daylight and too much artificial light at night, distorts these rhythms with downstream effects on mood. [18]
Trauma and adverse childhood events. These are well-known triggers, strongly predicting future mental-health risk, likely by activating the HPA axis and altering its function long term. [19] Even childhood bullying predicts chronic systemic inflammation into adulthood.
Loneliness. Social isolation, which our ancestors would have experienced only when separated or wounded, became wired to a pro-inflammatory immune response. Modern studies show loneliness raises pro-inflammatory cytokines that promote mental illness. [20]
Environmental triggers. Mold and mycotoxins, air pollution, and electromagnetic frequencies can all influence mental well-being. Moldy environments are strongly connected to depression via inflammatory cytokines, air pollution raises the risk of depression and bipolar disorder through neuroinflammation, and a slow accumulation of research suggests non-native EMFs may contribute by altering voltage-gated calcium channels that govern neurotransmitter release. [21]
Final thoughts
There is clearly more to mental health than chemical imbalances like low serotonin or dopamine. That does not mean chemistry plays no role, only that it is not the whole story. A growing body of evidence points to inflammation as an underlying issue in many cases of mood disturbance: people with mental-health disorders show the cardinal features of inflammation, giving healthy people inflammatory cytokines can induce depressive symptoms, and major depression is associated with brain changes that promote inflammation. So assessing the causes of inflammation, nutrient imbalances, and gut health matters.
Contrary to what the conventional paradigm suggests, mental illness is not a life sentence. By identifying the underlying causes and applying functional-medicine interventions, it is entirely possible to improve mental health and quality of life. This is education, not medical advice, and it is a starting point for a conversation with a clinician.
Your life is your medicine.
If something here rang true for you, the next step is a conversation. Start with a free consult, then we can work on your baseline together.
Reviewed by Dr. Daniel Gonzalez, DC.
