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Biological Basis of Mental Illness

Aunice Reed, M.A. in Marriage and Family Therapy from Touro University, M.S. in Addiction Counseling and B.A. in Psychology, Clinical Track.

Psyche (A Goddess In Greek mythology) kneeling on the edge of the water. She is thought to be the human soul archetype.

Psyche (A Goddess In Greek mythology) kneeling on the edge of the water. She is thought to be the human soul archetype.

Mental health refers to our overall psychological and social well-being. It references all of our feelings, thoughts and experiences throughout the lifespan. The state of our mental health drives choices we make, affects the quality of relationships we have and our ability to cope with the problems of day-to-day living.

Mental Health Diagnosis is Standardized Across the Globe: The DSM-IV

What causes people to become mentally ill? Mental illness has a biological basis; there are conditions within the individual’s brain or body in general, which express abnormal mental states. But “normal” is subjective, so an agreed upon understanding of what is meant by normal versus abnormal is needed. Health professionals agree to standard criteria for each mental health diagnosis as the tool for determining when someone in fact has a mental illness, and the level of severity. The Diagnostic and Statistical Manual of Mental Disorders DSM-5 from the American Psychiatric Association (2013) is the current version of criteria that all healthcare professionals refer to for purposes of diagnosing mental conditions in the United States and most places internationally.


Psychiatrists Focus Chiefly on Medication Management of Symptoms

In practice, medical doctors (e.g. psychiatrists and primary care physicians) tend to be more focused on the biological aspects of mental disease, while the main focus of other mental health clinicians are on psychological and social areas. Therapists and counselors do consider biological components, but it is not the principal emphasis for diagnostic or treatment purposes. In most practice scenarios, mental health clinicians manage the psychotherapeutic aspects of treatment, while a medical professional will be more concerned with medication management and medical conditions.

“The World Health Organization states that “health is complete physical, mental and social well-being and not merely the absence of disease.”

Vitruvian Man, drawn by Leonardo Di Vinci (c. 1490).

Vitruvian Man, drawn by Leonardo Di Vinci (c. 1490).

The Mental Health Wellness Continuum

Wellness and Illness are Never Static States

Health status can be viewed as occurring on a continuum, or scale where there the condition of optima health exists on one end and then illness on the opposite end. Always in flux, mental health and mental illness can be viewed through the same lens with mental health and mental illness existing at two opposite poles of the spectrum. Every individual has their quirky traits, phases and behaviors, but a person is considered to have a mental heath condition when diagnosable according to DSM-5 standards. Abnormalities are diagnosable, not just because they fall within the standard set of criteria, but when the individual experiences significant difficulties with day-to-day functioning. Symptoms persist, causing a considerable level of uncomfortability and distress.

Several factors figure into the etiology of mental illness and while biology is a component, it is not the only essential piece. So there isn’t any single, exact cause for mental illness. Biological, psychological and environmental (social) factors are all part of the basis of mental health conditions.


Biological Factors and Mental Illness

Many mental disorders are directly associated with and are linked to medical conditions:

Hypothyroidism - Refers to an underactive thyroid gland. Individuals with this medical condition commonly experience depressive symptoms which tend to disappear and alleviate with appropriate medical treatment.

Vitamin Deficiencies - Not getting an adequate level of certain vitamins and nutrients in the diet can cause issues with a person’s mental health. Pernicious anemia, caused by a lack of vitamin B12, affects the way oxygen is transported within the blood. It manifests symptoms of mood instability and irritability. Other common symptoms include: hallucinations, mania, dementia and paranoia. Another example is Beriberi, which develops when an individual lacks vitamin B1 (Thiamine). This too causes mental issues. Symptoms include problems with memory and sleep. It manifests as agitation, irritability, anxiety and depression. Due to lack of this important nutrient, the brain cannot convert glucose into energy, leading to its inability to function normally.

Other vitamin deficiencies having an adverse effect on mental health include:

  • Vitamin B9 (Folate) deficiency causes depression.
  • Vitamin D deficiency causes depression and other mood difficulties.
  • Hypocalcemia (low Calcium) leads to confusion, irritability and fatigue.
  • Vitamin C deficiency causes depression, fatigue and irritability.

Neurocognitive Disorders - Mental conditions can cause diminished functioning in cognitive processes such as with language, memory, attention and perception. These conditions are linked to medical pathologies like Alzheimer’s Disease, Traumatic Brain Injury or Parkinson’s Disease, for example. Neurocognitive disorders are not present at birth or do not develop early in life.

Neurodevelopmental Disorders - Mental conditions such as Autism Spectrum Disorder, Global Developmental Delay Disorder and Attention-Deficit Hyperactivity Disorder fall within this category. These diagnoses become noticeable during early life. Learning disorders and those concerned with speech pathologies are also neurodevelopmental. These conditions are typically related to biological diagnoses like Fragile X Syndrome, Down’s Syndrome, Cerebral Palsy and Fetal Alcohol Syndrome, for instance.

Substance Abuse - Drug and alcohol abuse cause neurochemical changes in the brain and its structure. These changes lead to abnormal brain function and mental health problems. In the United States, addiction is a treatment specialty of medicine defined by the American Society of Addiction Medicine as “a treatable, chronic medical disease involving complex interactions among brain circuits, genetics, the environment, and an individual’s life experiences. People with addiction use substances or engage in behaviors that become compulsive and often continue despite harmful consequences” (ASAM, 2019). Substance use disorders are also understood to be types of mental illnesses, such as Alcohol Use Disorder or Opioid Use Disorder (American Psychiatric Association, 2013).


There isn’t any single, exact cause for mental illness. Biological, psychological and environmental (social) factors are all part of the basis of mental health conditions.

Schizophrenia - Characterized by delusions, hallucinations and disorganized speech, schizophrenia causes the affected individual to experience and interpret reality in an abnormal way. This condition has a genetic predisposition, as it has a tendency to run in families. Structural brain abnormalities such as large lateral ventricles, myelin sheath irregularities in the cerebral cortex and decreased brain volume are common findings. Neurotransmitter dysfunction has been thought to be involved as well.

Anxiety - The core symptom of anxiety disorders is the triggering of a disproportionate response to stress, that may be experienced whether a stressor is present or not. A response to stress is regulated and controlled by the hypothalamic-pituitary-adrenal axis, or HPA within the brain. The amygdala and hippocampus regulate the HPA. If you are interested in learning more about these structures, See: The Human Limbic System: The Brain's Emotional Core.


"There are significant difficulties with day-to-day functioning. Symptoms persist, causing a considerable level of uncomfortability and distress."

The Role of Genetics: No Two Brains are the Same

While behavior is the by-product of brain functioning, the brain itself is the result of each individual’s genetics and environment which intersect with one another. Our genetics makes us all unique; it is likewise with the brain. One individual's brain is physically different from everyone else’s. As with a fingerprint, no two brains are identical. Additionally, personal experiences (history and background) leave a permanent imprint on the brain. Trauma and medical disease are examples of this. Furthermore, these differences, no matter how subtle they appear to be, cause the brain to be susceptible to even more changes. Subsequent experiences modify the brain which are expressed as physical changes and then show up in human behavior.


“The interplay between DNA and the environment is what makes each person unique” (Harvard University, 2017).

“The interplay between DNA and the environment is what makes each person unique” (Harvard University, 2017).

Understanding the Biology of Mental Illness

References

American Psychiatric Association. (2013). The diagnostic and statistical manual of mental disorders, DSM-5 (5th Ed.). Washington, D.C.: American Psychiatric Publishing.

American Society of Addiction Medicine. (2019). Definition of Addiction. Retrieved from asam.org

Harvard University Graduate School of Arts and Sciences. (2017). How stress can change your DNA. Retrieved from harvard.edu

World Health Organization. (2018). Mental health: Strengthening our response. Retrieved from who.int

This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.

© 2021 Aunice Yvonne Reed

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