Both involuntary dyskinetic movements and psychotic-like experiences (PLEs) are reported to be antecedents of schizophrenia that may reflect dysfunctional dopaminergic activity in the striatum. The present study compared dyskinetic movement abnormalities displayed by children with multiple antecedents of schizophrenia (ASz), including speech and/or motor developmental lags or problems, internalising/externalising problems in the clinical range, and PLEs, with those displayed by children with no antecedents (noASz).

The sample included 21 ASz and 31 noASz children, aged 9–12 years old. None had taken psychotropic medication or had relatives with psychosis. The antecedents of schizophrenia were assessed using questionnaires completed by children and caregivers. A trained rater, blind to group status, coded dyskinetic movement abnormalities using a validated tool from videotapes of interviews with the children.

ASz children reported, on average, ‘certain experience’ of 2.5 PLEs, while noASz children, by definition, reported none. The ASz children, as compared with noASz children, displayed significantly more dyskinetic movement abnormalities in total, and in the facial and the upper-body regions, after controlling for sex and age. Receiver operator characteristics analyses yielded high area under the curve values for the total score (0.94), facial score (0.91) and upper-body score (0.86), indicating that these scores distinguished between the ASz and noASz children with great accuracy.

Brief questionnaires identified children with multiple antecedents of schizophrenia who displayed significantly more involuntary dyskinetic movement abnormalities than children without antecedents. The presence of PLEs and dyskinesias could reflect early disruption of striatal dopamine circuits.

Birth cohort studies have shown that individuals who develop non-affective psychoses display subtle deviations in behaviour during childhood and adolescence. We had the opportunity to examine the widely used Child Behavior Checklist (CBCL) and the Youth Self-Report (YSR) to explore the antecedents of non-affective psychosis.

Based on a birth cohort of 3801 young adults, psychopathology was assessed at years 5 and 14 using the CBCL and/or the YSR. Screen-positive non-affective psychosis (SP-NAP) was assessed at year 21 by using the Composite International Diagnostic Interview (CIDI) or a self-report checklist. The association between childhood symptoms and SP-NAP was examined using logistic regression.

Of the cohort, 60 subjects were classified as SP-NAP. In males, SP-NAP was associated with higher scores: (a) on year 5 CBCL ‘Total’, ‘Aggression’ and ‘Social, Attention and Thought’ scores; (b) on year 14 CBCL ‘Social’, ‘Attention’ and ‘Delinquency’ scores, and (c) YSR ‘Total’ and many YSR subscores. These associations were less clear for females. Hallucinations at year 14 were associated with SP-NAP for both sexes. Boys with high ‘Total’ scores at both years 5 and 14 were at greatest risk of SP-NAP (a 5-fold risk), followed by boys and girls whose ‘Social, Attention and Thought’ scores either increased or remained high from years 5 to 14 (3- to 13-fold risk).

Individuals who screen positive for non-affective psychosis show increased psychopathology during childhood and adolescence. The psychopathological trajectory of children who go on to develop schizophrenia anticipates the heterogeneity associated with the full clinical syndrome.