Self-Injurious Behavior

Part 3: Genetics and the environment -- two heads of the coin

by Joy Simpson

"There are many possible genetic causes of Self-Injurious Behavior. The severe cases may very well be instances where genetics plays a significant role," says Stephen Schroeder. When looking at brain functions and behavior, genetic origins are certainly important. The role of the environment cannot be overlooked either. The circumstances of life ultimately affect the expression of any chemical imbalance in the brain. "Traumatic life events, eating, stress, even learning are all factors that can bring out -- or control -- a genetic condition like SIB," reports Schroeder.

Many forms of mental retardation are genetic. In certain kinds, SIB is so predictable that it is considered part of the disorder. In fact, scientists learn about SIB just from studying the origins of mental retardation. Mental retardation and SIB are linked in these genetic conditions: Lesch-Nyhan, Prader-Willi, Smith-Magenis, de Lange, and Fragile X.

For example, researchers have pinpointed the origin of the Lesch-Nyhan syndrome. The gene is on the X chromosome and the molecular location is an enzyme called HPRT. The genetic defect causes an overproduction of purine 5, and leads to large amounts of uric acid being stored in body fluids. Scientists also know that a deficiency of HPRT changes the structure and function of the brain, resulting in cognitive and neurological deficits -- and perhaps triggering SIB. However, SIB cannot be fully explained by the chemical process; scientists are also looking at the role of neurotransmitters with Lesch-Nyhan syndrome.

Genetic conditions do not destine a person to unrelenting self-abuse. "Treatment is possible and important," says Schroeder. Just as diabetes can never be cured, so too with SIB, the condition persists. But, people with diabetes can live out full lives by changing their eating patterns and taking insulin. With SIB also, education, behavioral supports, and sometimes medicine can change the way the behavior is expressed -- says Schroeder -- and significantly reduce the number of times it occurs. Because of advances in science, most individuals with SIB are no longer subject to repeated self-mutilation from biting, gouging and head banging. Persons with SIB can often live in community housing or at home with their families.

References
Schroeder, S.R., et al. (2001), Self-injurious behavior: Gene-brain-behavior relationships, Mental retardation and developmental disabilities research reviews, 7, 3-12.

Schroeder, S. R., Oster-Granite, M.L., and Thompson, T. (Editors) (2002), Self-injurious behavior: Gene-brain-behavior relationships. Washington, D.C.: American Psychological Association.

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