Childhood Symptoms May Predict Later Schizophrenia

For the first time, there is solid evidence linking psychotic symptoms in childhood to adult schizophreniform disorder, according to researchers. Study findings, which were published in the November issue of the Archives of General Psychiatry, reveal that children with psychotic symptoms are 16 times more likely than controls to have a schizophreniform diagnosis by the age of 26.

Twenty-five percent of children who, at age 11, were determined to have severe psychotic symptoms, met DSM-IV criteria for schizophreniform disorder later in life, according to Richie Poulton, Ph.D., and colleagues.

Participants in the study were members of the Dunedin Multidisciplinary Health and Development Study, a longitudinal study conducted in New Zealand of the health and behavior of a cohort born between April 1972 and March 1973. Cohort members represented the full range of socioeconomic statuses in New Zealand, according to the researchers.

“The remarkable thing about our findings,” Poulton told Psychiatric News, “is [how many of] our group of otherwise normal children reported odd psychotic-type symptoms and then went on to have a much higher chance of being diagnosed with schizophreniform disorders by the time they were 26 years old.”

Poulton, who is director of the Dunedin Multidisciplinary Health and Development Research Unit at the University of Otago, in Dunedin, New Zealand, also said that the link had been determined only for schizophreniform disorder, and not other psychiatric disorders.

According to the researcher,s they chose to use the more cautious label “schizophreniform disorder” because the diagnosis of schizophrenia should be applied only after the clinician has known and observed the patient’s illness for some time. By definition, schizophrenia involves the presence of symptoms for at least six months, while the schizophreniform disorder symptoms must persist for at least one month but less than six months.

These findings may not sound surprising to some, but evidence of childhood risk factors for schizophrenia has not been well supported in previous studies. For example, past evidence has been based on examination of archived information collected for some other purpose. Or, according to the researchers, studies have addressed the percentage of adults with schizophrenia who have had a risk factor for the disorder in their histories.

As part of the study, child psychiatrists administered the Diagnostic Interview Schedule for Children (DISC-C) to 761 children in New Zealand. During the interview, the children were asked about delusional beliefs and hallucinatory experiences and then were placed into three response categories—654 children who had no psychotic symptoms, 95 children who had weak psychotic symptoms, and 12 children who had severe psychotic symptoms.

When study subjects reached the age of 26, they were assessed again. A total of 9.5 percent of children with weak psychotic symptoms and 25 percent of children with severe psychotic symptoms, respectively, met criteria for schizophreniform disorder as adults.

Seventy percent of the children with severe psychotic symptoms exhibited one of the following symptoms at the age of 26, said researcher Terrie Moffitt, Ph.D.: hallucinations, delusions, disorganized speech, grossly disorganized or catatonic behavior, and negative symptoms, such as blunted affect. Moffitt, who is a clinical psychologist at the Social, Genetic, and Developmental Psychiatry Research Centre at the Institute of Psychiatry in London, explained that a smaller percentage—25 percent—exhibited enough symptoms to qualify for a formal diagnosis of schizophreniform disorder. “It is reasonable to predict,” added Moffitt, “that some of the study members with these symptoms will develop schizophrenia before their mid-30s, but we do not know which ones.”

Findings also show that as childhood psychotic symptoms increased in severity, so did the percentage of study members at age 26 who reported symptoms associated with social impairment, occupational impairment, and poor self-care habits.

In Poulton’s view, results from the longitudinal study carry a certain responsibility with them. “There is now a worldwide interest in trying to identify the early signs and symptoms of schizophrenia, mainly because it is thought that early intervention can be of benefit and may even change the course of the disease.” Poulton explained that historically, identifying specific risk factors has proven difficult and that the new findings offer hope that schizophrenia can be reliably identified earlier in life than previously thought. “However,” he added, “the findings need to be replicated in other samples before the implications for early intervention are known.”

The researchers are planning to reassess the study subjects at ages 31 and 32 and will document the outcomes of those subjects diagnosed with schizophreniform disorder at age 26. ▪