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Director’s Blog: A Growth Chart for the Mind

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For pediatricians and parents, one of the most important tools is decidedly low tech. The growth chart, a simple graph of the trajectory of the normal range of height, weight, and head circumference across age, is a vital tool for detecting problems in development. Even when a child is in the normal range, identifying a change from the 80th percentile at age 6 to the 20th percentile at age 8 can indicate a problem.

Imagine if we had a similar tool for cognitive and emotional development or for the development of select brain pathways. While not exactly a growth chart, a map of the development of various brain functions could help parents and providers know when to be concerned. A new paper just published online in JAMA Psychiatry provides the first picture of what a cognitive developmental chart looks like and how it might be used for children at risk for psychosis.1

Ruben Gur and his colleagues at the University of Pennsylvania tested children from ages 8 to 21 with a one-hour computerized battery of cognitive tests. The children were part of a large population-based study, the Philadelphia Neurodevelopmental Cohort, which included over 50,000 children who were seen at the Children’s Hospital of Philadelphia for general pediatric services, not for psychiatric services. All children were genotyped, nearly 10,000 received cognitive assessments, and a smaller subsample received neuroimaging.

The assessment included 12 different tests with measures of both accuracy and speed. Nearly two years ago Gur and his colleagues reported the effects of age and gender on these tests in 3,500 children.2 In that first report, they found that memory capacities had reached their apex by age 8, but that executive function and reasoning continued to improve into early adulthood. The new report is important because it focuses on over 2,000 children and adolescents with psychotic symptoms. Just as children with diabetes veer from the normal growth trajectory in a pediatrician’s growth chart, children and adolescents in the psychosis spectrum group had a lower predicted age relative to typically developing children, with a developmental lag observed especially in tests of complex cognition and social cognition. The delay ranged from 6 to 18 months and was present as early as age 8.

There are some shortcomings of this study. The design was cross-sectional, not longitudinal, so the trajectory of growth needs to be inferred across different individuals. And a one-hour battery cannot test for all cognitive domains. Nevertheless, Gur and his colleagues have given us the first large-scale maps of cognitive development with measures of both accuracy and speed. As others use this same instrument (which is freely available at https://penncnp.med.upenn.edu/request.pl ), the field should be able to develop normative data on hundreds of thousands of children, as has been done for height, weight, and head circumference. Ideally this will be extended to infants and developed in longitudinal studies so that trajectories of cognitive and emotional growth can be part of every child’s health record.

References

1 Gur RC et al. Neurocognitive Growth Charting in Psychosis Spectrum Youths.  JAMA Psychiatry. 2014 Feb 5. doi: 10.1001/jamapsychiatry.2013.4190. [Epub ahead of print]

2 Gur RC et al. Age group and sex differences in performance on a computerized neurocognitive battery in children age 8-21.  Neuropsychology. 2012 Mar;26(2):251-65. doi: 10.1037/a0026712. Epub 2012 Jan 16.