Genetic Schizophrenia Marker Appears Early in Childhood

A well-known physiological marker of genetic vulnerability to schizophrenia—saccadic intrusions into smooth-pursuit eye movements—has been found to occur as early as 6 years of age.

This finding comes from Randal Ross, M.D., an associate professor of psychiatry at the University of Colorado Health Sciences Center in Denver. He reported it in the April Journal of the American Academy of Child and Adolescent Psychiatry.

The discovery also has implications for schizophrenia treatment, he told Psychiatric News.

Ross recorded eye movement during a smooth-pursuit eye-movement task in 189 youngsters aged 6 to 15. Forty-nine of the children were already diagnosed with schizophrenia or schizoaffective disorder, 60 had first-degree relatives with schizophrenia, and 80 were typically developing children. He then looked to see how many of the children experienced saccadic intrusions.

The answer was 94 percent of the youngsters with schizophrenia or schizoaffective disorder, 50 percent of the youngsters with first-degree relatives with schizophrenia, and 19 percent of the typically developing children. What’s more, some of the subjects who experienced the intrusions were as young as 6, which is more than a decade before the age when schizophrenia symptoms usually begin to emerge.

Psychiatric News asked Ross whether screening children as young as age 6 for saccadic intrusions might pinpoint those who are at especially high risk of developing schizophrenia and thus lead to some way of preventing the development of schizophrenia as teenagers.

“No,” Ross replied, and for various reasons. For instance, whereas a fifth of the general population may experience saccadic intrusions, as this study shows, only a fraction of them ever develop schizophrenia.

Instead, Ross explained, the importance of his finding lies in a different area—demonstrating that at least one well-documented physiological sign of genetic vulnerability to schizophrenia occurs as early as age 6. And if saccadic intrusions occur as early as age 6, then other brain abnormalities underlying schizophrenia probably do so as well.

In fact, Ross continued, if saccadic intrusions are already present in children as young as 6, then the intrusions might already be there in infancy, perhaps even before birth. He and his colleagues are now conducting studies to find out when they first appear.

If such abnormalities are already present at birth or before, any efforts to reverse them will undoubtedly have to be attempted at this time, Ross stressed. The notion of doing so may sound daunting, he acknowledged, but it is not necessarily impossible. In fact, he said, he and his colleagues are researching the neural mechanisms in the brain that cause saccadic intrusions and are exploring possible prenatal strategies for correcting them—say, “prenatal dietary supplements following the model of what prenatal folic acid did for preventing spina bifada.”

The study was funded by the Veterans Administration Research Services and Eli Lilly.

An abstract of the study, “Early Expression of a Pathophysiological Feature of Schizophrenia: Saccadic Intrusions Into Smooth-Pursuit Eye Movements in School-Age Children Vulnerable to Schizophrenia,” can be accessed on the Web at www.jaacap.com by clicking on “Online Archives” and searching under the April issue. ▪