How is the brain involved in the development of a mental disorder?
The human brain is an amazing organ. It controls memory and learning, the senses (hearing, sight, smell, taste, and touch) and emotion. It also controls other parts of the body, including muscles, organs, and blood vessels.
The brain also is a very complex structure. It contains billions of nerve cells—called neurons—that must communicate and work together for the body to function normally. The neurons communicate through electrical signals. Special chemicals, called neurotransmitters, help move these electrical messages from neuron to neuron.
Information is fed into the brain through the senses. What is heard, felt, tasted, seen, or smelled is detected by receptors in or on the body and sent to the brain through sensory neurons. The brain decides what to do with the information from the senses and tells the body how to respond by sending out messages via motor neurons. For example, if a person puts his or her hand near something hot, the sense of touch tells the brain about the heat, and the brain sends a message to the muscles of the arm to move the hand away. Another type of neuron—called interneurons—connects various neurons within the brain and spinal cord, which together make up the central nervous system.
Just as there are different types of neurons, there also are different types of chemical neurotransmitters. Researchers studying mental illness believe an imbalance of the neurotransmitting chemicals in the brain contributes to the development of mental illness. This chemical imbalance makes it difficult for messages to move from neuron to neuron and for the brain to function normally. As a result, the brain might "misunderstand" what the senses are telling it and/or might not send the right response messages back to the body. The imbalance might be inherited or triggered by a significant psychological or physical event, such as the onset of puberty.
What other biological factors are involved in mental illness?
There are other biological factors that might be involved in the development of mental illness. These include the following:
Genetics (heredity)
Many mental disorders run in families, suggesting that the disorders—or more accurately, a susceptibility (greater likelihood of being affected) to the disorders—might be passed on in families through genes, the material that contains the instructions for the function of each cell in the body. (Genes are the basic biological unit of heredity and are passed to children from their parents.) Experts believe many mental disorders are linked to multiple genes—not just one, as with many diseases—which is why a person inherits a susceptibility. The disorder itself occurs from the interaction of multiple genes and other factors—such as stress, abuse, or a traumatic event—which can influence, or trigger, the disorder in a person who has an inherited susceptibility.
Infections
Certain infections have been linked to brain damage and the development of mental illness or the worsening of its symptoms. For example, a condition known as pediatric autoimmune neuropsychiatric disorder associated with strep, or PANDAS, has linked an infection caused by the Streptococcus bacteria to the development of obsessive-compulsive disorder and other disorders in children.
Brain defects or injury
Defects in or injury to certain areas of the brain also have been linked to some mental disorders.
Prenatal damage
Some evidence suggests that a disruption of early fetal brain development or trauma that occurs at the time of birth—for example, loss of oxygen to the brain—might be a factor in the development of certain disorders, such as autism.
Other factors
These include nutrition and toxins, such as lead, which may play a role in the development of mental disorders.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. This document was last reviewed on: 2/14/2005...#4268
