Neuropsychological follow-up in neonatal screening: issues, methods and findings

There are several ongoing studies of psychological outcome in children identified through neonatal screening with phenylketonuria, congenital hypothyroidism or congenital adrenal hyperplasia. These studies document the reduction in mental retardation, learning difficulties and behaviour problems associated with neonatal screening. They also describe other behavioural changes resulting from these disorders. Some behavioural changes are transient or preventable with early diagnosis and treatment, whereas some appear to be irreversible, reflecting permanent brain effects of abnormalities associated with the disease. Despite the variety of disorders studied, there are commonalities in approach and issues, including a developmental neuropsychological perspective resulting in behavioural assessments specific to the disorder and its likely manifestations, a recognition that behaviour may change across time in association with brain development and an understanding of the neural mechanisms underlying the behavioural changes. Assessments go beyond IQ, and include specific intellectual abilities, social behaviour, temperament, behaviour problems and identity. Behavioural changes are related to specific characteristics of the disease and its treatment, including the timing of exposure to abnormal hormones and/or neurotransmitters, the severity of the disease, and the age at initiation and adequacy of treatment. These studies provide information about the ways in which hormones and neurotransmitters affect the development and ongoing function of the brain, and an understanding of the ways in which neonatal screening results in improved psychological outcome. They also provide models for psychological follow-up of other disorders detected through neonatal screening.