Abstract
Schizophrenia researchers wonder if schizophrenia is a neurodevelopmental or neurodegenerative condition. Data from our life-course study suggest it may be both. We previously reported that children who later develop schizophrenia show slowed growth in fluid cognitive abilities across ages 7 to 13 years (1), consistent with a neurodevelopmental model of schizophrenia. With new data at midlife (2), we think we have documented that these same individuals show some cognitive degeneration (i.e., loss of acquired cognitive abilities) from before to after the onset of schizophrenia. Usually, the mental abilities of an individual are interpreted against a standard of performance that is normative, where normative is defined as age typical. Childhood and adult tests tap the same abilities, but they often use age-appropriate test materials. However, the clearest evidence that neuropsychological decline in schizophrenia represents a loss of acquired cognitive abilities would be seen if the test given at follow-up precisely matched the initially administered test, as Bora (3) notes. In the Dunedin Multidisciplinary Health and Development Study, two tests given in adulthood (age 38) were identical to those given in childhood (age 13): the Grooved Pegboard Test and the Rey Auditory Verbal Learning Test.