According to the National Survey on Drug Use and Health, more than 43 million people in the United States suffer from some form of mental illness. This pervasive health issue creates continuing challenges for individuals, families, and society at great cost, both financially and emotionally.

While scientists continue to study mental illness, its causes, and how to help those who struggle with it, there is still a lot that is unknown about what leads to mental illness and who is most likely to be susceptible. Still, there is a basic understanding about the various causes of and contributors to mental health disorders.

Article Snapshot

The underlying causes of mental illness:

  1. Genetics
  2. Trauma
  3. Brain Damage or Brain Injury
  4. Infections
  5. Fetal Damage or Injury
  6. Malnutrition
  7. Substance abuse
causes of mental illness

1. Genetics

Mental illness tends to run in families. This is true not only within types of disorders – such as families with multiple members who tend toward alcoholism – but across types as well. People whose family members struggle with one type of mental illness have a higher risk of having any kind of mental health disorder. In particular, a person who grew up with a parent who had a mental illness is more likely to develop mental illness, according to the American Society for Child and Adolescent Psychiatry. When both parents have a mental illness, the child’s risk is even greater.

Nevertheless, having a family member with a mental health disorder does not guarantee that an individual will develop one. There are other factors that come into account. For example, a child whose parent has a mental health disorder may be less likely to develop mental illness if there are certain protective factors, such as if the child:

  • Gets adequate nutrition and exercise
  • Enjoys and excels in school
  • Has a constructive, supportive social network
  • Develops positive relationships with other adults
  • Feels loved and cared for by the mentally ill parent

2. Trauma

Another contributor to the development of mental health issues is emotional or physical trauma, particularly when experienced as a child or youth. As described in Trauma Informed Care in Behavioral Health Sciences, trauma – especially early in life – can result in changes to various brain and body communication centers, such as:

  • The limbic system, which governs emotions and memories
  • The hypothalamus, pituitary, and adrenal system, which regulates the stress response
  • The pleasure and reward systems, including the body’s own, endogenous opioid response system

There’s still a lot to learn about the mental damage caused by trauma and how it feeds into mental illness. However, it is known that people who suffer trauma at a young age can experience delays or challenges in brain development and may develop both physical and mental health disorders as a result.

3. Brain Damage or Brain Injury

When the brain is directly physically damaged, either from birth or through an acute physical injury, mental illness can result. An article from Neuropsychiatric Disease and Treatment discusses the variety of disorders that can occur after traumatic brain injury, such as:

  • Depression
  • Mania
  • OCD
  • PTSD
  • Psychosis

Various research studies have demonstrated that 21-49 percent of those who experience traumatic brain injury receive a psychiatric diagnosis within the year following the injury. Repeated, milder brain injury, such as concussion, can result in later development of mental health disorders as well.

4. Infections

Some severe infections can cause brain damage that results in mental illness. For example, recent research has demonstrated that a strep infection in childhood can result in a condition referred to as PANDAS, or pediatric autoimmune neuropsychiatric disorder associated with strep, which manifests as a severe type of obsessive-compulsive disorder (OCD). In fact, an article from the OCD Foundation discusses the fact that other infections seem able to result in a similar condition.

Some people believe that having a high fever as a result of illness can cause a mental health disorder; however, this does not generally seem to be the case. However, fever and hyperthermia, or heat stroke, can increase issues for those who are already dealing with mental illness.

5. Fetal Damage or Injury

Some risk for mental illness can result from damage that occurs before the individual is even born. An article from the Saturday Evening Post discusses research showing that women who are exposed to certain viruses while pregnant are more likely to have children who develop mental health disorders. This is thought to be a result of the mother’s immune system responding to the virus, not the virus itself, but positive links have been demonstrated with infections including:

  • The flu
  • Rubella (German measles)
  • Toxoplasmosis
  • Genitourinary infections

Specifically, 30 percent of the risk of developing schizophrenia comes from prenatal flu exposure and exposure in the first three months of pregnancy can increase risk of schizophrenia by as much as five times. However, because the damage is caused by the mother’s own immune system, almost any virus can be a risk.

A mother who uses or abuses alcohol or other drugs can also affect the baby’s potential for developing mental illness later in life. Fetal alcohol syndrome is a well-known result of alcohol abuse in pregnancy, and can result in a high risk of mental illness developing in childhood. According to the Journal of the Canadian Academy of Child and Adolescent Psychiatry, this can result in a range of mental health disorders, with depression and anxiety disorders being most common.

6. Malnutrition

A study from Social Science and Medicine details the effect that malnutrition can have on mental heath by analyzing information from recent periods of famine that occurred in China and other countries. The result demonstrated that malnutrition, especially in early life, can cause damage to mental function that results in a range of mental illnesses. Again, this is thought to be a result of damage to brain development; however, the exact mechanisms are still being studied.

7. Substance Abuse

Other mental health disorders and substance abuse often occur together. In many cases, this is because the individual is using a substance to self-medicate the symptoms of a pre-existing mental health disorder. However, as described by the National Institute on Drug Abuse, substance use sometimes precedes mental illness, and can be considered a cause.

Substance abuse can have profound effects on the brain, changing brain chemistry and even causing reductions or increases in the structures of the brain that make up the affected systems. For example, this can be seen in:

Sometimes, the chemical and physical disruption caused by drug abuse can result in mental illness developing in those who already had a high risk of mental health disorders because of one of the other factors above. As a result of this substance abuse, protective factors that may have kept the mental illness from manifesting originally can be diminished, resulting in the mental illness manifesting.

When It’s More Than Substance Abuse

We Address & Treat Underlying Co-Occurring Issues

The many causes of mental health disorders are still being researched to find answers about how to treat and prevent them from occurring. In the meantime, it helps to know that there is a level of control that can be exerted over these causes: in the cases of preventable factors, such as substance abuse, malnutrition, and alcohol or drug abuse, it is possible for individuals to make decisions that give themselves a better chance at beating the risk and avoiding or managing mental illness.