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Functional Psychiatry: Treating Common Conditions with the Functional Approach


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The New York Times published a thought-provoking article titled “When Will We Solve Mental Illness?” In the article, science reporter Benedict Carey discusses the failure of conventional psychiatry to produce effective cures for mental illnesses, despite decades of scientists toiling in pharmaceutical research. However, rather than calling for a more in-depth investigation into the root causes of mental illness, Carey suggests that researchers focus their efforts on better understanding the genetics of mental illness so that targeted “cures” can be developed. (1)

Functional psychiatry
Functional psychiatry emphasizes interventions that address root causes, like increasing social connectedness to address loneliness. iStock/fizkes

While Carey’s heart is in the right place, it is articles such as this one that perpetuate the conventional view of mental illnesses as diseases that can be solved with single cures. Despite decades of research, science has failed to produce effective and safe long-term treatments for mental illness. As a practitioner, you’ve likely encountered patients who don’t seem to respond to traditional treatment—or, if you or a loved one has a mental illness, you’ve perhaps encountered this frustrating situation firsthand. The good news is that, within the field of Functional Medicine, a promising new approach to psychiatry is taking shape: functional psychiatry. It is poised to fill the pressing need for effective mental healthcare in our society. Read on to learn how a Functional Medicine approach to psychiatry successfully addresses the underlying causes of mental illness, improving long-term mental health outcomes for patients.

Functional psychiatry emphasizes treating the root cause of a disorder rather than masking symptoms with prescription drugs. Check out this article for more information, including behavioral and dietary changes that support better mental health. #functionalmedicine #unconventionalmedicine

What Is Functional Psychiatry?

The Functional Medicine approach is focused on preventing or reversing illness by addressing the root cause. As Functional Medicine practitioners, our goal is to offer patients true healthcare. We don’t simply suppress symptoms through medication or try to “manage” a disease; we promote whole-body health.

According to Integrative Medicine for Mental Health, an educational organization dedicated to the advancement of an integrative approach to mental health, functional psychiatry embraces that whole-body approach to patient health by using methods like “individualized metabolic testing, nutritional therapies, and dietary interventions,” sometimes together with conventional approaches like psychotherapy. Functional psychiatry provides mental health practitioners with a framework to better understand common mental conditions and a toolkit to address them.

That shift in approach can have a dramatic impact on patients who have struggled under conventional treatment plans. While conventional methods work wonders for some people and can even be life-saving, for those with difficult-to-treat conditions, they offer little hope of relief. Functional psychiatry is designed to help people—while creating more meaningful and rewarding work for practitioners.

The rates of chronic illness are rising. Conventional medicine can’t stop this epidemic, but practitioners trained in the Functional Medicine approach can.

In the ADAPT Practitioner Training Program, we’re teaching practitioners like you how to apply the principles of Functional Medicine to your practice. We give you the tools you need to improve the health and lives of your patients by addressing the root causes and focusing on prevention, not symptom management.

The ADAPT Practitioner Training Program can help you create a more effective and rewarding practice. Find out more.

A Brief Overview of Common Mental Health Disorders

Mental illnesses are becoming increasingly common in our modern-day world. According to the National Alliance on Mental Illness, a shocking one in five American adults currently experiences mental illness, and 17 percent of U.S. adolescents have a mental illness. (2) Before diving into an in-depth discussion on the Functional Medicine approach to psychiatry, let’s briefly discuss some of the most common mental illnesses experienced in our society.


More than 17 million U.S. adults, or 7 percent of the population, have experienced a depressive episode over the past year, making depression one of the most common mental illnesses. (3) Depression is characterized by:

  • Profound feelings of sadness
  • Hopelessness
  • Fatigue
  • A loss of interest in activities

Changes in sleep and appetite may also occur. Left untreated, the consequences of depression on physical health, functionality, and relationships can be devastating. While some people may experience just one depressive episode in their lives, more often than not, depression recurs.

Women are twice as likely as men to experience major depression. Women also experience a variety of types of depression, including: (4)

While selective serotonin reuptake inhibitors (SSRIs) have long been the go-to drugs for depression, research indicates that the clinical response to SSRIs is abysmal, with only 40 to 60 percent of people with depression experiencing symptomatic relief and a mere 30 to 45 percent experiencing remission. (5)

SSRIs and other antidepressants also have many side effects, including: (6, 7)

  • Weight gain
  • Sexual dysfunction
  • Depletion of beneficial gut bacteria
  • Withdrawal symptoms upon discontinuation

Several studies have drawn a correlation between SSRI use and dementia. (8) Concerningly, 25 percent of people on SSRIs have taken the drugs for a decade or more, an alarming statistic considering that no SSRI safety studies have lasted for more than two years. (9)


Anxiety disorders affect over 18 percent of the U.S. population each year and include conditions ranging from generalized anxiety disorder to obsessive-compulsive disorder (OCD) and social anxiety disorder. (10)

SSRIs are commonly prescribed for anxiety disorders. However, other anti-anxiety medications, such as benzodiazepines, are also widely used. Benzodiazepines have addictive properties, and their long-term use is linked to cognitive dysfunction, sexual dysfunction, and increased anxiety and depression. (11, 12, 13)

Bipolar Disorder

Bipolar disorder is characterized by dramatic shifts in mood, energy, and activity levels. Approximately 2.8 percent of American adults have experienced bipolar disorder in the past year, and a shocking 89 percent of people with bipolar disorder are seriously impaired, unable to carry out the activities of daily living. (14) Bipolar disorder is notoriously recalcitrant to pharmaceutical treatment, with a meager rate of remission. (15)

Post-Traumatic Stress Disorder

Post-traumatic stress disorder (PTSD) affects people from all walks of life, including former soldiers, victims of sexual abuse, and people who were bullied as children. The lifetime prevalence of PTSD is 6.8 percent (16), and treatment relies heavily on psychotherapy, medication, or a combination of the two. Treatment-resistant PTSD is a common and frequently disabling condition that adversely impacts all aspects of life, from physical health to personal relationships. (17)


Schizophrenia is an elusive, severe condition with a lifetime prevalence of 1 percent in the U.S. population. (18) It impairs a person’s ability to think, feel, and behave clearly, and symptoms include:

  • Hallucinations
  • Delusions
  • Disorganized speech
  • Lack of pleasure
  • Flat affect
  • Trouble with speech
  • Social withdrawal

Symptoms usually start between the ages of 16 and 30; some patients may experience a “prodrome” phase, in which changes in their personality begin to appear before the full onset of symptoms.

Eating Disorders

Eating disorders encompass an array of food- and body-image-related disorders, including:

  • Anorexia nervosa
  • Atypical anorexia nervosa (severe food restriction and other anorexic behaviors without low body weight)
  • Bulimia
  • Binge eating disorder
  • Purging disorder
  • Night eating syndrome
  • Muscle dysmorphia, also referred to as “bigorexia” (19, 20)

Atypical anorexia nervosa, or severe food restriction and other anorexic behaviors in “normal weight” and overweight individuals, tend to be overlooked altogether by the medical community. (21, 22) Eating disorders are also not just the domain of young women—these disorders are increasingly affecting men, middle-aged women, and older women. (23, 24)

The long-term remission rate for eating disorders is pretty dismal, with just 50 percent of patients with anorexia nervosa and 75 percent of patients with bulimia achieving remission at the 10-year mark. (25) These figures do not account for subclinical disordered eating and weight-control behaviors, which may affect a significant portion of our population, particularly “health-conscious” folks. (26, 27, 28)

Two Theories of Mental Illness

Why are mental illnesses so common in our modern-day society? Scientists interested in understanding the root causes of mental illness have proposed two broad theories: the evolutionary mismatch theory and the pathogen-host theory of mental illness.

Mental Illness as an Evolutionary Mismatch

I’ve previously discussed the role of evolutionary mismatch in chronic disease development. The theory of evolutionary mismatch posits that there is a significant mismatch between our genes, biology, and physiology, and the modern-day environment in which we live. Our bodies expect specific dietary and lifestyle inputs, based on our ancestral genetic programming, yet our modern environment provides us with inputs to which we are not adapted. Our bodies respond aberrantly to these inputs, ultimately becoming dysfunctional.

Based on this theory, depression, anxiety, and other mental illnesses are physical manifestations of a profound mismatch between our ancestral biology and our modern environment. (29) The validity of this theory becomes abundantly clear when we examine the relationship between the Western diet and lifestyle habits and poor mental health. Anorexia nervosa and bulimia nervosa may have an evolutionary mismatch component, with intrasexual competition among females (and, to a smaller extent, males) for mates interacting with our media-saturated environment, causing distorted body image and disordered eating. (30, 31)

According to the evolutionary mismatch theory, mental illness is a non-adaptive by-product of modern environmental and social conditions. This concept contrasts with the pathogen-host theory of mental illness, which posits that depression, and possibly other mental illnesses, is a by-product of an adaptive response by the body to clear infections.

The Pathogen-Host Theory of Depression

A growing body of research indicates that depression and inflammation tend to occur together. According to the pathogen-host theory of depression, this relationship may reflect an ancient mechanism: When our ancestors developed an acute infection, their bodies launched an acute inflammatory response to combat pathogens; the unintended consequence of this inflammation was depression. However, as human civilization grew and our immune systems changed, this once-adaptive mechanism ceased to be useful. Instead, humanity began to experience chronic inflammation and, subsequently, chronic mental illnesses. (32)

Another version of this theory suggests that, in ancient times, humans with immune incompetence developed depression to protect themselves from acquiring infections from other humans and shunt their energy toward repair processes, because depression naturally induced social avoidance and energy conservation.

Why Are There No Universal “Depression Genes?”

Are there genetic risk factors in humans that are reliably linked to mental illness? Genome-wide association studies have failed to find universal genetic single-nucleotide polymorphisms that confer an increased risk of mental illness across all racial and ethnic groups. The exception is schizophrenia, which has common genetic risk factors in several populations. (33) The mysterious case of the “missing depression/mental illness genes” may be attributed to the different pathogen protection genes humans acquired in disparate racial and ethnic groups throughout evolution, in response to the unique threats they faced in their environments. (34) As a result, specific genetic variants may drive inflammatory anti-pathogen processes and depression in individuals from one racial/ethnic group, but not another.

Therefore, unlike the evolutionary mismatch theory, the pathogen-host theory suggests that mental illness represents the vestiges of a once-adaptive mechanism. According to this theory, genetic risk factors for depression are maintained in the human genome, not due to a misstep of evolution but because, by enhancing our immune defenses against pathogens, they provide a net survival and reproductive advantage.

11 Underlying Causes of Mental Illness

Based on the evolutionary mismatch and pathogen-host theories of mental illness, we can better understand why certain aspects of human biology and the modern-day diet and lifestyle are associated with mental illness. In this section, let’s discuss each contributing factor in turn:

  • Infection and immune dysregulation
  • The standard American diet
  • Blood sugar dysregulation
  • Sedentary lifestyle
  • Impaired neurogenesis
  • Faulty gut–brain axis signaling
  • Blue light and circadian rhythm disruption
  • Trauma
  • Loneliness
  • Genetic variants and mental illness
  • Environmental triggers, such as electromagnetic fields (EMFs) and mold

1. Infection and Immune Dysregulation

Dr. Charles Raison is a forward-thinking psychiatrist and proponent of the pathogen-host theory of depression. In his research, Dr. Raison has found that inflammatory cytokines are consistently upregulated in people with depression, suggesting that human depression evolved out of sickness. (35)

Today, many people deal with chronic low-level infectious stressors, such as viral infections and gut microbial imbalances, rather than the acute infections that our ancestors faced. Chronic infection leads to chronic inflammation, which, in turn, enhances the conversion of the amino acid tryptophan to a compound called kynurenine. Kynurenine is converted into a metabolite called quinolinic acid, which has neurotoxic and neuroinflammatory effects. Excessive quinolinic acid has been identified in a variety of mental illnesses, including depression, bipolar disorder, and schizophrenia. (36) Quinolinic acid causes apoptosis of astrocytes, oligodendroglia, and neurons. It is, therefore, no wonder that chronic inflammation has repeatedly been implicated in the development of depression. Infectious diseases are known to cause dysfunction of the autonomic nervous system, which is significantly affected in almost all major mental health disorders. (37)

Several infections have been directly associated with mental health disorders:

  • Lyme disease causes a variety of neuropsychiatric symptoms, including depression, anxiety, and suicidality. (38)
  • Infection with Group A Streptococcus in children can trigger pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection, or PANDAS, a form of OCD. (39)
  • Viral infections, including cytomegalovirus and herpesvirus 6, and inflammation are implicated in schizophrenia and bipolar disorder. (40, 41)
  • Infection with the intracellular parasite Toxoplasma gondii is linked to both schizophrenia and bipolar disorder. (42)

Clearly, tiny microbes can have significant effects on our brains and behavior!

Many inflammatory mediators are also upregulated in mental illnesses, even in the absence of an apparent infectious trigger. Mediators that are upregulated in mental illness include the inflammatory cytokines interleukin 1 beta (IL-1β) and interleukin 6 (IL-6) and the acute phase reactant C-reactive protein. (43, 44)

2. The Standard American Diet

Time and time again, the standard American diet has been linked to poor mental health. In epidemiological studies, the consumption of ultra-processed foods is associated with depression. (45, 46) In preclinical research, a diet high in refined carbohydrates has been found to induce neuroinflammation and anxiety-like behavior in mice. (47) While we cannot ignore the fact that people with depression and anxiety may be more likely to consume processed foods, confounding this relationship, I think it’s safe to say that the standard American diet has no place in mental healthcare.

3. Blood Sugar Dysregulation

Insulin is one of the body’s primary hormones that regulate blood sugar. Research indicates that, via its effects on blood sugar control, insulin influences central nervous system (CNS) function. Insulin also impacts neuronal circuitry formation and synaptic plasticity, thus playing an essential role in mental health. Preclinical research indicates that when the brain becomes insulin resistant, dopaminergic signaling is impaired, and anxious and depressive behaviors may surface. (48) In human studies, insulin resistance is linked to depression and bipolar disorder. (49)

Insulin treatment has been found to attenuate the hypothalamus–pituitary–adrenal (HPA) axis response to psychosocial stress and to boost mood and memory. (50, 51) These findings suggest that improving insulin homeostasis may support a healthy mood.

4. Sedentary Lifestyle

Consistent physical activity is linked to good mental health, whereas a sedentary lifestyle is linked to anxiety and depression in people of all ages. (52, 53) The adverse mental health effects of a sedentary lifestyle may be mediated by decreases in brain-derived neurotrophic factor (BDNF) and endocannabinoid system (ECS) activity, which promote neuroplasticity and the “runners high,” respectively. (54)

5. Impaired Neurogenesis

Neurogenesis is the process by which new neurons grow and develop from neural stem cells. A growing body of research indicates that impaired neurogenesis is a central feature in mental illness. (55, 56) Many factors impair neurogenesis, including: (57, 58, 59, 60, 61)

  • High cortisol levels caused by chronic stress
  • Low levels of neurotrophic factors such as BDNF
  • Chronic systemic inflammation
  • Alterations in the gut microbiota
  • Traumatic brain injury

6. Faulty Gut–Brain Axis Signaling

The gut–brain axis is a bidirectional signaling pathway linking the enteric nervous system of the gut, the gut microbiota, and the CNS. It is highly complex, transmitting messages from the gut to the CNS, and vice versa, via inflammatory mediators, gut microbial metabolites, stress hormones, neurotransmitters, and the vagus nerve. When it comes to functional psychiatry, the gut–brain axis cannot be ignored. (62)

A growing body of research indicates that factors that disrupt the intestinal barrier and gut microbiota, particularly early in life, increases the risk of future mental illness. (63) A disrupted gut microbiome predisposes an individual to gut infections and inflammation, thus circling back to the pathogen-host theory of mental illness.

Several types of gut bacteria produce neurotransmitters identical to our own, including the calming neurotransmitter gamma-aminobutyric acid (GABA) and the “feel-good” neurotransmitter serotonin. (64) The Lactobacilli family contains a variety of GABA- and serotonin-producing species that are highly susceptible to depletion by antibiotics and a Western diet, leading to alterations in host neurotransmitter signaling.

Intestinal dysbiosis contributes to the development of mental illness by inducing an influx of inflammatory lipopolysaccharide (LPS) into the systemic circulation. LPS increases the body’s production of neurotoxic quinolinic acid, which has repeatedly been linked to mental illness.

A growing area of interest in the mental health-gut microbiota domain is our emerging understanding of the role that gut microbes play in eating disorders. Recent research suggests that gut microbes that produce a molecule called ClpB may cross-react with one of the body’s own appetites- and emotion-regulating hormones, alpha-Melanocyte-stimulating hormone, or alpha-MSH. The molecular mimicry between ClpB, which is produced by many pathogenic microbes such as Salmonella and Yersinia enterocolitica, and alpha-MSH may partially explain the increased anxiety and decreased food intake characteristic of anorexia nervosa. (65)

Interestingly, 64 percent of individuals with eating disorders have been diagnosed with IBS. Crohn’s disease and ulcerative colitis are also common in patients with eating disorders. While some of these gut changes may be caused by starvation and other abnormal eating patterns, people with an eating disorder have disrupted gut microbiotas before the onset of illness. (66)

7. Blue Light and Circadian Rhythm Disruption

Our circadian rhythms are cycles of biological patterns that occur on an approximately 24-hour schedule and influence many aspects of our behavior and physiology, including mood and cognition. Light exposure (or lack thereof) is a powerful cue governing human circadian rhythms. Up until the advent of electricity, our ancestors lived in harmony with the natural cycles of light and dark. Conversely, our modern-day lifestyles deficient in sun exposure during the day and high in artificial light exposure at night represent a profound evolutionary mismatch, altering our circadian rhythms and having adverse downstream effects on our mental health.

Even small amounts of dim artificial light at night may impair mental health; “indoor dim light,” such as that emitted from an alarm clock, has been found to penetrate the eyelids and be detected by retinal photoreceptors, which are central in the regulation of circadian rhythms. This low level of artificial light exposure is linked to an increased risk of depression in adults, even after controlling for sleep quality and chronic health conditions. The negative relationship between artificial light at night, circadian rhythms, and mental health appears to be mediated by melatonin suppression. (69)

Shift work, or work that takes place outside of the typical schedule of 9:00 a.m. to 5:00 p.m. and often involves evening and early morning shifts, is another example of circadian rhythm disruption. Shift work also appears to increase the risk of mental illness by altering melatonin production and circadian rhythms. (70)

8. Trauma

Traumatic life events are well-known triggers for mental illness. Adverse childhood events strongly predict an individual’s future risk of mental health disorders, possibly by activating the HPA axis and altering its function over the long term. (71, 72) Sadly, childhood bullying, which is all too common, has been found to predict chronic systemic inflammation, a risk factor for mental illness, well into adulthood. (73) Other traumatic events that may trigger mental illness range from serving in the military to caring for a sick parent or loved one, a stressful job, or academic stress.

9. Loneliness

Our modern society is suffering from an epidemic of loneliness. A study published by the health services organization Cigna reported that 46 percent of U.S. adults feel lonely “sometimes” or “always,” offering a sad reflection on our current culture. (74)

According to evolutionary psychology, the roots of loneliness and mental illness go way back. Our hunter–gatherer ancestors lived in communal settings, where social isolation would have occurred only if someone became separated from the group, perhaps through wounding. As a result, social isolation (aka loneliness) became associated with a potent pro-inflammatory immune response designed to target the types of pathogens to which an individual would have been exposed in such a situation. (75) Fast forward to today, and it is clear that social isolation and inflammation are still intrinsically linked.

Animal experiments that induce social isolation have been found to also cause an inflammatory response. Furthermore, some individuals are more genetically sensitive to social isolation than others, producing higher blood levels of pro-inflammatory cytokines tumor necrosis factor-alpha and IL-6 when they experience social isolation. (76) The increase in inflammatory cytokines, in turn, may promote mental illness. Indeed, loneliness and living alone are among the most significant risk factors for mental illness. (77)

10. Genetic Variants and Mental Illness

While genome-wide association studies have failed to find consistent genetic risk factors for mental illness across all racial and ethnic groups, several genetic variants are linked to mental illnesses in subgroups of the global population.


Variants in the methylenetetrahydrofolate reductase (MTHFR) gene can lead to reduced activity of the MTHFR enzyme. This enzyme is crucial for regulating inflammation and neurotransmitter production. As such, MTHFR variants are linked to anxiety, depression, autism, and schizophrenia. (78) Going along with the pathogen-host theory of depression, a mild deficiency in MTHFR enzyme activity caused by MTHFR variants has been found to confer protection against malaria and cytomegalovirus, indicating that these variants had an evolutionary advantage. (79, 80)


The glutamic acid decarboxylase (GAD) gene codes for the GAD enzyme, which initiates the decarboxylation of the excitatory neurotransmitter glutamate into GABA, the body’s primary calming neurotransmitter. GAD variants may decrease the conversion of glutamate to GABA, resulting in anxiety, neuroticism, and major depressive disorder. (81)


The catecholamine-O-methyltransferase (COMT) gene codes for the production of the COMT enzyme, which breaks down catecholamine neurotransmitters such as dopamine, epinephrine, and norepinephrine. COMT variants may slow the breakdown process of these neurotransmitters, resulting in anxiety and OCD. (82, 83, 84)


Neuronal PAS Domain Protein 2 (NPAS2) is a protein that regulates the transcription and translation of circadian rhythm-related genes. Variants in the NPAS2 gene, which codes for the production of the NPAS2 protein, are associated with bipolar disorder. (85)

11. Environmental Triggers

The environments in which we work and live can have a significant impact on our mental health, though few mental health practitioners recognize this connection.

Mold and Mycotoxins

Have your patients ever lived or worked in a moldy environment, and subsequently developed depression or anxiety? Exposure to indoor mold and mycotoxins can trigger neuropsychiatric symptoms by increasing inflammatory cytokines. (86) You can learn more about mold illness and testing for mold in my article “Mold Illness: What It Is, 5 Common Misconceptions, and Prevention” and my interview with indoor environmental professional Mike Schrantz, “How to Test Your Home for Mold.”

Air Pollution

We all know that air pollution can make us cough and have difficulty breathing, but did you know it may also promote psychiatric disorders? Ambient air pollution increases the risk of depression and bipolar disorder by upregulating neuroinflammation. (87) The risk appears to be particularly significant when air pollution exposure occurs during the first 10 years of life.


Of all the environmental triggers that promote mental illness, non-native EMFs may be the most underappreciated. The term “non-native EMF” refers to EMFs that have been manufactured by humans, and that are emitted from items such as cell phone towers, routers, and smartphones, in contrast to EMFs that occur naturally on the Earth. A small but steadily growing body of research indicates that non-native EMFs may contribute to depression and other neuropsychiatric issues by altering the activity of voltage-gated calcium channels in the brain, which govern neurotransmitter release. (88, 89) Even though the scientific evidence is preliminary, at the very least, I recommend using a speakerphone, earbuds, or a Bluetooth headset when communicating on your phone; not sleeping with your phone in your bedroom; and turning off your WiFi router at night.

10 Behaviors to Support Your Patients’ Mental Health

1. Eating an Ancestral, Anti-Inflammatory Diet

As nutritionist Lindsay Christensen previously discussed in “Nutrition and Mental Health: What’s the Connection?,” nutrition has a significant impact on mental well-being. While a processed, refined standard American diet is correlated with an increased risk of mental illness, an ancestral, anti-inflammatory diet centered around whole, nutrient-dense foods is associated with robust mental health. (90)

Given the strong relationship between gluten sensitivity and neuropsychiatric health issues, I highly recommend celiac disease testing and non-celiac gluten sensitivity testing, through a lab such as Cyrex. If the results are positive, a gluten-free diet may do wonders for improving your patients’ mental well-being. (91)

The B-complex vitamins, particularly folate, vitamin B6, and vitamin B12, are essential cofactors in neurotransmitter production. (92) A deficiency of any one of these nutrients may impair mental health, so make sure your patients are eating foods rich in these nutrients. Folate is found in:

  • Dark leafy greens
  • Beef liver
  • Brussels sprouts
  • Avocado

Vitamin B6 is found in:

  • Poultry
  • Fish
  • Pork
  • Eggs
  • Bananas
  • Spinach
  • Sweet potatoes

Vitamin B12 is found almost exclusively in animal foods, so if your patients are not already eating red meat, poultry, and fish, reincorporating some of these foods into their diet may greatly benefit their mental health.

Vitamin D plays a critical role in supporting mental health by modulating inflammatory pathways in the brain. (93) A balance between zinc and copper is also crucial for optimizing mental health, due to the roles these minerals play as cofactors in dopamine, norepinephrine, and epinephrine production. (94) Magnesium deficiency is associated with an increased risk of depression and anxiety, so make sure your patients are eating plenty of magnesium-rich foods such as dark leafy greens, nuts, and cacao. Omega-3 fatty acids from seafood and dietary polyphenols, compounds found in colorful plant foods, may support a healthy mood by optimizing the membrane fluidity of neurons and beneficially modulating the gut microbiota, respectively. (95, 96)

Last but not least, a very low intake of cholesterol may increase the risk of mental illness and suicidality. If your patients have very low levels of cholesterol, they may want to boost their intake of healthy cholesterol-containing foods such as egg yolks and identify other possible underlying causes of the low cholesterol level. (97, 98)

2. Supporting Gut Microbes

Disruption of the gut microbiota has a significant impact on mental health. However, the gut microbiota is malleable, and research indicates that probiotics and prebiotics can improve both gut microbiota composition and mental health. A probiotic containing Bifidobacterium bifidum, B. lactis, Lactobacillus acidophilus, L. brevis, L. casei, L. salivarius, and L. lactis has been found to alleviate sad mood in participants without pre-existing mental illness. Bifidobacterium longum has been found to lower depression scores in patients with IBS. (99, 100)

Even notoriously treatment-resistant mental illnesses may respond to pre- and probiotics: A spectrum of Lactobacilli and Bifidobacteria plus fructooligosaccharides was discovered to improve both physical and psychological symptoms in a small group of subjects with bipolar disorder, while supplementation with Lactobacillus rhamnosus strain GG and Bifidobacterium animalis subsp. lactis as an adjunct to conventional medical treatment reduced rehospitalization rates in patients with bipolar disorder with acute mania. (101, 102)

The beneficial effects of prebiotics and probiotics on mental health are attributed to their anti-inflammatory properties and their ability to produce GABA and serotonin, thus normalizing neurotransmission.

3. Optimizing Sleep

If you’ve ever gone through several nights of sleep deprivation, you’ve experienced firsthand the adverse effects of poor sleep on mood. A growing body of research indicates that insufficient and poor-quality sleep over the long term significantly increases the risk of mental health issues. Optimizing sleep can do wonders for your patients in alleviating symptoms. Patients who need help with optimizing their sleep and improving their sleep hygiene should:

  • Limit exposure to artificial light for one to two hours before bed by wearing a pair of blue-light-blocking glasses. Exposure to full-spectrum artificial light at night, beyond just the blue light emitted from electronic devices, suppresses melatonin production. (103, 104)
  • Sleep in a completely dark room, free of outdoor light pollution and digital devices such as glowing alarm clocks. Blackout shades should be purchased if necessary.
  • Keep the bedroom cool, between 60 and 67 degrees Fahrenheit. The human body is designed to experience a drop in body temperature at the end of the day; this drop affects neural circuits that create a healthy sleep cycle. (105) Research has found that the range of 60 to 67 degrees is an ideal ambient temperature for inducing this critical drop in body temperature and restorative sleep.
  • Consider using supplemental melatonin in the short term. Melatonin, a crucial sleep- and circadian rhythm-regulating hormone, may be a beneficial adjunct therapy for depression and bipolar disorder via its circadian rhythm-aligning effects. (106, 107)

Some people benefit from using a sleep tracker, such as an Oura ring. Sleep trackers can help offer insight into sleep habits and identify areas that need improvement.

4. Exercising

Few interventions show more promise for supporting optimal mental health than exercise. Exercise shifts the tryptophan pathway away from the production of neurotoxic quinolinic acid, implicated in a variety of mental illnesses, toward the production of serotonin. (108, 109, 110)

Exercise also increases the body’s production of anti-inflammatory signaling molecules and BDNF, which supports neuroplasticity and a healthy mood. (111)

Endurance exercise may be especially beneficial for mental health due to its stimulatory effects on the ECS, the same system that mediates the neurobiological effects of Cannabis. (112) Circling back to our discussion of evolution and mental health, scientists propose that ECS signaling in response to aerobic exercise evolved out of our ancestors’ needs to travel long distances on foot when foraging and hunting; ECS activation would have made such experiences pleasurable, thus enhancing survival.

Finally, yoga may also benefit mental health, reducing depression and alleviating schizophrenia psychopathology, by increasing vagal tone, BDNF release, and serotonin and GABA neurotransmission. (113, 114)

5. Treating Depression with Heat

Saunas have recently become all the rage for supporting heart health and longevity; however, a lesser-known body of research suggests that a form of heat therapy may also have benefits for mental health!

Dr. Raison, one of the developers of the pathogen-host theory of depression, is also an ardent proponent of heat for alleviating depression. In an article published in JAMA Psychiatry, Dr. Raison and his co-authors found that just one session of “whole-body hyperthermia,” a therapy that offers a magnitude of heat similar to a sauna, significantly alleviated depression scores in subjects with major depressive disorder. (115) The antidepressant effects of heat have been noted in several other clinical trials, as well. (116)

There are two proposed mechanisms by which heat exposure may alleviate depression:

  1. Heat exposure activates heat shock proteins, which are protective against stress-induced depression. (117)
  2. High temperatures make certain types of pathogenic bacteria unwind, addressing the potential infectious component of depression.

Importantly, research indicates that the body needs to reach an internal temperature of at least 101.3 degrees Fahrenheit for an individual to experience antidepressant effects.

Your patients don’t need a $50,000 whole-body hyperthermia machine at home to experience the mood-boosting effects of heat. A dry sauna or an infrared sauna will do just fine. The warmer the body is before entering the sauna, the better; I recommend doing approximately 30 minutes of light- to moderate-intensity aerobic activity before the sauna to help the body reach the ideal internal temperature of 101.3 degrees Fahrenheit.

While hot yoga has not been studied in the context of specific mental illnesses, it does reduce cortisol reactivity to stress in women. (118) Perhaps hot yoga will soon emerge as another “therapy” for depression, just like sauna use!

6. Using Bright Light Therapy

Bright light therapy has been recommended as a treatment for seasonal affective disorder in both conventional and integrative medical circles for at least a decade; however, research demonstrates that bright light therapy also helps people across the depression spectrum by aligning the circadian rhythm. (119) There are a variety of bright light devices available on the market, but Alaska Northern Lights has excellent options with lights of all sizes and price points.

7. Seeking Nature Exposure

Spending time in nature is absolutely essential for our mental health. Research shows that accessibility to and total time spent in green space is positively associated with subjective mental well-being. (120) Furthermore, the practice of “forest bathing,” or shinrin-yoku in Japanese, has been found to significantly decrease depression and anxiety. (121, 122) If your patients can find a park, path, or nature preserve nearby where they can regularly reconnect with nature, they can experience some of these benefits for themselves.

8. Improving Social Connectivity

When it comes to Functional Medicine and health, many people tend to dive all in on diet changes, supplements, and exercise, while forgetting the importance of one key factor: social connectivity. Loneliness and psychosocial stress, caused by bullying or merely feeling that one “doesn’t fit in,” profoundly harm our mental well-being. Conversely, nurturing meaningful connections with friends and family throughout the lifetime supports a resilient, positive mental state. (123)

Importantly, research suggests that much of our social connectivity should take place in real life rather than online. Prolonged use of social networking sites may actually increase depression, and specific subgroups, such as adolescents and college-age women, may be especially susceptible to the harmful mental health effects of social media use. (124, 125)

9. Playing

I wrote at length about the importance of play for overall health in my previous article “10 Benefits of Play.” Play increases stress resilience in both children and adults, and it has a significant effect on mental health. (126, 127) Simple playful activities, like playing with a dog at the park, engaging in a favorite hobby, or horsing around with children, can increase joy.

10. Using Mind-Body Therapies

No discussion of Functional Medicine and psychiatry would be complete without covering various forms of mind-body therapy. Meditation, mindfulness, vagus nerve exercises, eye movement desensitization and reprocessing (EMDR), and cognitive behavioral therapy are just a few of the options for mind-body therapies available today.

Meditation and Mindfulness

Meditation really needs no introduction—it is all over the media today, touted for its benefits ranging from improved productivity and concentration to deeper sleep. Research indicates that meditation can benefit people with depression and anxiety. Meditation programs have been found to result in small-to-moderate reductions in psychological stress, alleviating depression and anxiety. (128) Meditation may support mental well-being by inducing “coherence,” a neuroscience term that refers to synchronous neural activity in the brain. (129) It also balances the immune system, possibly addressing the pathogen-host aspect of depression, and increases neuroprotective BDNF. (130, 131)

Mindfulness can be cultivated in a meditation practice, but it can also be accessed in the normal activities of daily life. Mindfulness training, synchronized with meditation, beneficially rewires the brain. (132) It reduces anxiety and depression and promotes fear extinction, making it a possibly beneficial therapy for PTSD. (133, 134)

Vagus Nerve Exercises

The vagus nerve is the critical “wire” that connects the gut with the brain, exerting a profound impact on gut–brain axis communication and mental health. Vagus nerve stimulation via an implanted device or a non-invasive transcutaneous electrical stimulation are U.S. Food and Drug Administration-approved therapies for epilepsy and depression (135, 136). However, an expensive medical device isn’t necessary to improve the function of the vagus nerve. Many interventions, including biofeedback, meditation, yoga, breathing exercises, and other quick DIY exercises, can be done at home to improve the health of the vagus nerve:

  • Biofeedback is a valuable tool for self-activating the vagus nerve. HeartMath is a biofeedback device and app that guides people through exercises to improve heart rate variability, a critical component of vagus nerve function.
  • Meditation, mindfulness, and yoga improve vagal tone.
  • DIY exercises such as gargling and singing can help improve vagal tone. Check out the book Accessing the Healing Power of the Vagus Nerve for more DIY vagus nerve exercises.
  • Specific probiotic species stimulate the vagus nerve, including B. longum and L. rhamnosus. (137, 138)


EMDR is a form of psychotherapy that was initially designed to alleviate psychological distress associated with traumatic memories. (139, 140) It uses eye movements or other forms of bilateral stimulation, such as devices that emit a gentle vibration, one held in each hand, to alternately stimulate the two hemispheres of the brain. Via bilateral brain stimulation, EMDR changes maladaptive neural networks.

EMDR has expanded beyond the realm of trauma and is now being used by therapists to treat recurrent depression, anxiety, eating disorders, and addictions. (141, 142, 143, 144)

A 2012 study found that EMDR helped 77 percent of adults with a psychotic disorder and comorbid PTSD. (145) Research also indicates that the benefits of EMDR can be maintained long-term. (146)

Cognitive Behavioral Therapy

Cognitive-behavioral therapy has long been considered the “gold standard” form of therapy for mental illnesses. (147) It is a form of talk therapy that involves changing patterns of thinking or behavior that are unhelpful for supporting one’s well-being. Instead, distorted thinking and behavioral patterns are replaced with: (148)

  • Facing one’s fears
  • Developing confidence in one’s abilities
  • Learning to calm one’s mind
  • Using problem-solving skills to cope with difficult situations

Nutrients and Nutraceuticals for Mental Health

While diet can go a long way toward supplying the body with the nutrients needed to support mental health, supplementing with certain nutrients and nutraceuticals may offer great benefits in certain situations.


Research indicates that up to 50 percent of American adults are deficient in magnesium; magnesium deficiency is a risk factor for depression and anxiety. (149) Correcting this deficiency with supplemental magnesium may alleviate mild-to-moderate depression and subjective anxiety and stress. (150, 151)


5-Hydroxytryptophan (5-HTP) is a clinically effective serotonin precursor that has been used for decades in integrative medicine as a supportive treatment for depression. (152) However, it should never be used by individuals who are currently on an SSRI, as it may lead to excessive serotonin levels.


GABA is the body’s primary calming neurotransmitter. Research shows that many mental illnesses involve relative GABA deficiency. Supplementation with GABA has been found to ameliorate anxiety, possibly by interacting with the enteric nervous system. (153) It may also be possible to increase the endogenous GABA levels with a probiotic that contains GABA-producing species, such as Lactobacillus and Bifidobacteria.


One area in which cannabidiol (CBD) truly shines is the treatment of anxiety disorders. CBD modulates neurotransmission and alleviates anxiety through its effects on the ECS and a variety of non-endocannabinoid receptors, including 5-HT1a serotonin receptors. (154)


Inositol is a vitamin-like substance, sometimes referred to as vitamin B8, that mediates cell signaling in a variety of tissues and organs. It influences the action of insulin, assisting with blood sugar control, which has downstream effects on mood. Inositol also balances serotonin and dopamine, and has been found to reduce panic attacks, improve depressive symptoms, and balance bipolar disorder symptoms alongside omega-3 fatty acids. (155156, 157, 158) Extremely high doses—18 grams per day—have been found to alleviate OCD. (159)


Zinc plays numerous critical roles in the nervous system. It is an inhibitory modulator of the N-methyl-D-aspartate receptor, attenuating excessive excitatory neurotransmission. (160) It is also crucial for neurogenesis and modulates synaptic plasticity. (161, 162)

Randomized controlled trials support the use of zinc as adjunctive therapy for major depressive disorder. (163) It has also been found to improve attitudes toward eating and food in young patients with anorexia nervosa compared to placebo pills. (164)

Other Functional Psychiatry Tools: Psychedelics, MDMA, and More

Psychedelics are no longer just the domain of long-haired hippies and raving partygoers; these drugs are a fascinating, emerging area of interest in the field of psychiatry, particularly as an adjunct to therapy for difficult-to-treat mental health conditions such as PTSD. 3,4-Methylenedioxymethamphetamine (MDMA), psilocybin, and lysergic acid diethylamide (LSD) have all shown preliminary benefits in the treatment of severe mental health disorders.

In mental illness treatment, psychedelics are designed to be used in controlled, therapeutic treatment settings; these are not intended to be DIY interventions.


MDMA is a psychoactive drug that became popular as a recreational drug in the 1960s and ‘70s. However, as Dr. Michael Mithoefer and I discussed in a recent episode of Revolution Health Radio, MDMA is breaking away from its reputation as a drug of abuse and demonstrating new therapeutic properties in the treatment of PTSD. While the mechanisms of action are complex, MDMA appears to alleviate PTSD by reducing fear activity in the amygdala, increasing prefrontal cortex activity, and enhancing neuroplasticity, thus enabling the resolution of emotional trauma. (165) Excitingly, these beneficial changes may be sustained over the long term.

The therapeutic use of MDMA for PTSD is best used under the guidance of a MAPS-trained psychiatrist in conjunction with psychotherapy. As part of PTSD therapy, the drug is taken three times, with each dose occurring a month apart.


Psilocybin, a psychoactive alkaloid found in “magic mushrooms,” also offers therapeutic potential in mental health disorders. It improves treatment-resistant depression and depression associated with a terminal illness, possibly by acting as an agonist of the 5-HT2a serotonin receptor. (166, 167) When the serotonergic receptors are blocked, the beneficial neurochemical effects of psilocybin do not occur.


LSD is a hallucinogen that was first synthesized in 1938 by chemist Dr. Albert Hofmann. It can be derived from alkaloids derived from ergot, a type of fungus that grows on rye and other cereal grains. Via its interactions with serotonergic receptors, LSD increases neural plasticity in the cerebral cortex and may be indicated in major depressive disorder and existential anxiety associated with life-threatening diseases. (168)


Ketamine, an anesthetic and long-time illicit party drug, is the new kid on the block for heavy-duty mental health treatment. Like other psychedelics, it appears to change the structure of neurons, facilitating recovery from severe depression and PTSD. (169, 170) Interestingly, it has also demonstrated antioxidant and anti-inflammatory properties. (171)

Contrary to what the conventional medical paradigm has led us to believe, mental illness is not a life sentence. With the identification of critical underlying causes and the implementation of Functional Medicine-based interventions, it is entirely possible to improve your patients’ mental health and their overall quality of life.