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Self-Injurious Behavior

Part 2: Breakthroughs in drug treatment

No drug to date has been created specifically for self-injurious behavior (SIB). To find a medicinal treatment, scientists are testing drugs approved for psychiatric disorders.

Risperidone originally came on the market for persons with schizophrenia. A group of researchers at the University of Kansas obtained permission to run clinical trials on risperidone for the treatment of SIB. Stephen Schroeder, Ph.D. headed the team that includes Jessica Hellings, M.D., a professor of psychiatry at the Medical School, and Jennifer Zarcone, Ph.D., a research scientist at the Schiefelbusch Institute for Life Span Studies. Their clinical studies showed that half of the persons who took risperidone experienced a 50 percent reduction of SIB episodes. In all the patients but one, the drug reduced 25 percent of the incidents.

Risperidone acts as a modulator adjusting the amount of serotonin and dopamine in the brain. Serotonin and dopamine regulate learning, reward, and emotions. Schroeder decided to pursue risperidone as a remedy because data from animal models showed a link between self-injury and an imbalance of the brain chemistry. His hypothesis is that SIB may be caused by a depletion of dopamine and an excess of serotonin in the basal ganglia region of the brain.

Approximately one-quarter of the persons with SIB do not show long-term benefits from "behavioral" interventions -- changes made in the environment, or new learned patterns of behavior. In this instance, medicine plays an especially important role in treatment. Schroeder's study is noteworthy because he restricted participation to those persons who experience repeated, severe bouts of SIB and have not found relief elsewhere. With risperidone, he was able to show a significant reduction in the number of SIB incidents.

A complementary approach has been put forward by Curt Sandman, University of California at Irvine. His research involves the opioid system which regulates the sensation of pain. He has also been successful in treating the most difficult cases of SIB -- with drugs called opiate-blockers. Naltrexone changes the brain chemistry in persons with an elevated pain threshold. The inability to feel normal pain is another compelling explanation for SIB.


"It is interesting," says Schroeder, "the opioid receptors for pain are located in the same area of the brain as the dopamine receptors that also influence SIB. It is likely these two systems interact and are part of a larger circuitry of neurons." Some patients may react well to the drug risperidone and others to naltrexone. This may be evidence that persons experiencing SIB don't all have the same diagnosis, according to Schroeder. The success of various treatments may depend on the person's unique brain chemistry.

References

King, B.H. (1993). Self-injury by people with mental retardation: A compulsive behavior hypothesis. American Journal on Mental Retardation, 98, 93-112.

McAdam, D.B., Zarcone, J.R., Hellings, J., Napolitano, D.A., and Schroeder, S.R. (2002). Effects of risperidone on aberrant behavior in persons with developmental disabilities: II. Social validity measures. American Journal on Mental Retardation, 107, 261-269.

Thompson, T., Symons, F., Delaney, D., and England, C. (1995). Self-injurious behavior as endogenous neurochemical self administration. Mental Retardation and Developmental Disabilities Research Reviews, 1, 137-148.

Zarcone, J., Hellings, J., Crandall, K., Resse, R.M., Marquis, J., Fleming, K., Shores, R., Williams, D., and Schroeder, SR (2001). Effects of risperidone on aberrant behavior of persons with developmental disabilities: I. A double-blind crossover study using multiple measures. American Journal on Mental Retardation, 106, 525-538.

Read Part 3: GENETICS AND THE ENVIRONMENT -- TWO HEADS OF THE COIN


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