Static and dynamic cognitive deficits in childhood preceding adult schizophrenia: a 30-year study

Abstract

Objective: Premorbid cognitive deficits in schizophrenia are well documented and have been interpreted as supporting a neurodevelopmental etiological model. The authors investigated the following three unresolved questions about premorbid cognitive deficits: What is their developmental course? Do all premorbid cognitive deficits follow the same course? Are premorbid cognitive deficits specific to schizophrenia or shared by other psychiatric disorders?

Method: Participants were members of a representative cohort of 1,037 males and females born between 1972 and 1973 in Dunedin, New Zealand. Cohort members underwent follow-up evaluations at specific intervals from age 3 to 32 years, with a 96% retention rate. Cognitive development was analyzed and compared in children who later developed schizophrenia or recurrent depression as well as in healthy comparison subjects.

Results: Children who developed adult schizophrenia exhibited developmental deficits (i.e., static cognitive impairments that emerge early and remain stable) on tests indexing verbal and visual knowledge acquisition, reasoning, and conceptualization. In addition, these children exhibited developmental lags (i.e., growth that is slower relative to healthy comparison subjects) on tests indexing processing speed, attention, visual-spatial problem solving ability, and working memory. These two premorbid cognitive patterns were not observed in children who later developed recurrent depression.

Conclusions: These findings suggest that the origins of schizophrenia include two interrelated developmental processes evident from childhood to early adolescence (ages 7-13 years). Children who will grow up to develop adult schizophrenia enter primary school struggling with verbal reasoning and lag further behind their peers in working memory, attention, and processing speed as they get older.

FIGURE 1. Schematic Representation of Three Hypotheses of the Developmental Course of Premorbid Cognitive Functioning in Schizophrenia^a

^a The green line represents healthy comparison subjects and the red line represents children who grew up to meet diagnostic criteria for schizophrenia.

FIGURE 2

Childhood IQ Scores for Subjects Who Grew Up to Meet Diagnostic Criteria for Schizophrenia or Recurrent Depression and for Healthy Comparison Subjects

FIGURE 3. Mental Age Verbal Comprehension Scores by Assessment Age Among Children Who Later Developed Adult Schizophrenia or Recurrent Depression and Healthy Comparison Subjects^a

^a Data illustrate mean scores (green line represents healthy comparison subjects [N=556]; red line represents children who grew up to meet diagnostic criteria for schizophrenia [N=35]; blue line represents children who grew up to meet diagnostic criteria for recurrent depression [N=145]). The results show nonstandardized estimates of the differences between groups in the intercept and linear slope along with corresponding t tests and significance values from the growth-curve models.

FIGURE 4. Mental Age Perceptual Organization Scores by Assessment Age Among Children Who Later Developed Adult Schizophrenia or Recurrent Depression and Healthy Comparison Subjects^a

^a Data illustrate mean scores (green line represents healthy comparison subjects [N=556]; red line represents children who grew up to meet diagnostic criteria for schizophrenia [N=35]; blue line represents children who grew up to meet diagnostic criteria for recurrent depression [N=145]). The results show nonstandardized estimates of the differences between groups in the intercept and linear slope along with corresponding t tests and significance values from the growth-curve models.

FIGURE 5. Mental Age Freedom From Distractibility Scores by Assessment Age Among Children Who Later Developed Adult Schizophrenia or Recurrent Depression and Healthy Comparison Subjects^a

^a Data illustrate mean scores (green line represents healthy comparison subjects [N=556]; red line represents children who grew up to meet diagnostic criteria for schizophrenia [N=35]; blue line represents children who grew up to meet diagnostic criteria for recurrent depression [N=145]). The results show nonstandardized estimates of the differences between groups in the intercept and linear slope along with corresponding t tests and significance values from the growth-curve models.