Physiological Causes & Explanations for Mental Illness

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  • 0:06 Physiological Psychology
  • 1:34 Infections
  • 3:07 Malnutrition
  • 4:08 Metal Poisoning
  • 5:32 Lesson Summary
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Lesson Transcript
Instructor: Natalie Boyd

Natalie is a teacher and holds an MA in English Education and is in progress on her PhD in psychology.

There are many factors that can affect a person's mental health, including physiological issues. In this lesson, we'll look at three major physical causes of psychological problems: infection, malnutrition, and metal poisoning.

Physiological Psychology

Hector suffers from autism, a psychological disorder that involves issues with socializing, communication, and behavior. Hector's mom Kelly is worried about what might have caused Hector to be autistic. Was he born that way? Is it because she's a bad mom? Or, is there some other explanation for his problem?

Psychologists don't always agree on what causes mental illness. Some believe that psychological problems spring from problems in childhood that remain unresolved. Others believe that genetics can explain most mental illnesses. Still others think that psychological disorders are caused by learning bad habits.

Physiological psychology is the study of the physical basis of thoughts, behaviors, and feelings. For example, physiological psychology might say that Hector's autism is caused by brain abnormalities, which are caused by some type of biological problem.

Many studies have shown that there are brain differences in people with a variety of mental issues. From depression to schizophrenia to autism, many psychological disorders can be traced to abnormalities in the brain. But, what causes the neurological anomalies? That's what physiological psychology tries to figure out.

Let's look a little closer at some common physiological explanations for mental issues, including viral infections, malnutrition, and metal poisoning.


Remember Hector? He's suffering from autism. Kelly, his mom, worries that maybe he's autistic because she's a bad parent. For many years, that was what psychologists believed: cold and unloving parents could cause their children to become autistic.

But, brain scans showed that there were neurological abnormalities that caused the autistic symptoms. For the past few decades, then, the question has become, 'If autism has a neurological basis, what causes the brain anomalies?' There are many theories, and scientists don't agree on which theory is correct. One theory with scientific support is the possibility that viral infections during pregnancy or early childhood could change the way the brain develops, causing the symptoms of autism.

There are studies that show correlations between viral infections and autism and studies that show no correlation between the two, so it is impossible to know for sure how strong the link is between the two of them.

For other mental illnesses, though, there is a very strong link between infection and mental illness. Schizophrenia, for example, has strong links to pre- and post-natal infections. Though studies can't show that schizophrenia is caused by infection, it is a risk factor for the disease.

Likewise, there are connections between obsessive-compulsive disorder and the strep infection. Some children who have had a strep infection develop OCD or OCD-like behaviors.


Though there are several mental illnesses that are connected to infection, it is far from the only possible physiological cause of mental illness. Malnutrition can also play a role in the development of psychological disorders. Sometimes, the malnutrition is in infancy and early childhood, and other times, it is linked to maternal malnutrition during pregnancy.

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