Head Injury May Tip Schizophrenia Scales

Avoiding being hit on the head with a golf ball may be one way of partially ducking Alzheimer’s disease, recent evidence suggests (Psychiatric News, September 1, 2000). But it may also be a way of reducing the incidence of schizophrenia, at least for people at genetic risk of the disease.

So suggests a study conducted by Dolores Malaspina, M.D., and colleagues at the New York State Psychiatric Institute in New York City and reported in the March American Journal of Psychiatry.

Jonathan Silver, M.D., a clinical professor of psychiatry at New York University School of Medicine and president-elect of the American Neuropsychiatric Association, calls the study “superb.” And he considers it especially important, he told Psychiatric News, since “there has been very little good work on brain injury and schizophrenia because it is difficult to study.” And one reason it has been difficult to study, he explained, is that people with schizophrenia don’t usually end up in the brain-injury treatment system, but rather in the mental health system.

Malaspina and her colleagues zeroed in on some 600 individuals who had at least two first-degree relatives with schizophrenia, that is, they were persons who were presumably at genetic risk of schizophrenia. In fact, some of the study subjects had schizophrenia themselves. Data about these subjects had been collected as part of the National Institute of Mental Health Genetics Initiative for Schizophrenia and Bipolar Disorders—a cooperative project involving six university sites. Malaspina and her team then used the data that had been collected to see whether they could find any link between brain injury and schizophrenia. They could, they report.

For example, when they compared the rates of brain injury for subjects who had been diagnosed with schizophrenia with those who had not, they found a threefold increase in head-injury rates among those with schizophrenia.

One might ask, of course, whether the link between head injury and schizophrenia was due to schizophrenia’s causing head injury, not the other way around. Malaspina and her colleagues do not believe, however, that this was the case.

One reason, she explained to Psychiatric News, is that whereas the analysis included head injuries both before and after schizophrenia, “if you restricted it to head injuries before illness, you saw the same thing. Head injury before illness increased the risk.”

Another reason Malaspina and her coworkers believe that head injury is a risk factor for schizophrenia is that they not only analyzed data from the approximately 600 subjects who were part of the schizophrenia pedigree group, but also compared those data with data from some 1,300 persons who had at least two first-degree relatives with bipolar disorder and who were thus presumably at genetic risk for that disorder. When the researchers compared the rate of brain injury in the schizophrenia pedigree with that in the bipolar group, they found that the rate was significantly higher in the former. In the researchers’ view, this finding implies that a genetic predisposition to schizophrenia may also be capable of predisposing a person to head injury.

But how might a genetic predisposition to schizophrenia open a person to risk of head injury? Malaspina and her team offered a possible explanation: “Schizophrenia genes may increase exposure to head trauma, with head trauma further increasing the risk for schizophrenia.”

And how might schizophrenia genes increase exposure to head trauma? Malaspina and her colleagues proffer a possible explanation here as well: Schizophrenia genes could code for difficulty paying attention, and inattention in turn could open a person to accidents and head injury. Indeed, difficulty paying attention has long been noted as one of the symptoms of schizophrenia. In fact, it may be not only a vulnerability factor for schizophrenia, but also one of the earliest indicators of the disease (Psychiatric News, March 16).

Silver said that he believes that this could indeed be the case—that persons with a genetic predisposition to schizophrenia might inherit difficulty paying attention, or perhaps a slowness to react, that would then make them more vulnerable to head injury.

“How often have you almost been in an accident,” he asked, “where you slammed on the brakes or swerved and just missed? That has happened to just about everybody. It doesn’t take much to imagine that if there is some abnormality in reaction time, that some of those things that are ‘just misses’ for most of us are not ‘just misses’ [for certain schizophrenia-prone persons].”

Regardless of how a predilection for schizophrenia might also open a person to head injury, Silver thinks the study by Malaspina and her coworkers has some practical implications. “Most psychiatrists—in fact, most health professionals—are unaware of the neuropsychiatric sequelae of traumatic brain injury,” he asserted. “So they don’t ask their patients if they ever had a traumatic brain injury or don’t ask detailed questions, not realizing how much the brain injury can impact etiology of their symptoms....So I think that any well-done research that increases the awareness of traumatic brain injury is extremely helpful.”

And since almost all the subjects whom Malaspina and her colleagues studied had mild brain injury, he added, the study has another implication as well: “Even mild brain injuries are potent enough to cause this effect.”

The study, “Traumatic Brain Injury and Schizophrenia in Members of Schizophrenia and Bipolar Disorder Pedigrees,” is posted on the Web at ajp.psychiatryonline.org/cgi/content/full/158/3/440. ▪