Neurological Soft Signs, Cognition in Childhood, Attention Deficit Hyperactivity Disorder and Lifetime Major Depressive Disorder

Background: Neurological soft signs (NSS), subtle but abnormal motor and sensory signs and involuntary movements, have been implicated as risk factors for a number of psychiatric and neurodevelopmental disorders. Prior studies were based on small clinical samples, did not control for important confounding factors or examine domain or age specificity. Here we investigate the associations between NSS and multiple domains of cognitive functioning, Attention Deficit Hyperactivity Disorder (ADHD) and its subtypes and finally with lifetime diagnosis of major depressive disorder (MDD) and its age of onset in a large, population-based cohort, while adjusting for important confounding factors. Methods: We analyzed data from the Collaborative Perinatal Project (CPP), that followed the offspring of a pregnancy cohort till the age of seven and its follow up project, the New England Family Studies (NEFS) that followed the adult offspring of the Providence and Boston sites of the CPP. We adjusted for a wide array of confounding factors, including demographic variables as well as risk factors for brain injury and aberrant neurodevelopment. Results: NSS were associated with poor cognitive performance across all domains with no specificity. Each additional soft sign was associated with approximately 4 units drop in any cognitive score. NSS were associated with increased odds of all subtypes of ADHD. Each additional soft sign was associated with 70% increase in the odds of ADHD diagnosis. However, NSS was not associated with a higher risk of major depressive disorder in childhood compared to adolescence or adulthood. Conclusions: There is an association between NSS and poor cognitive performance and ADHD that is not attributable to established risk factors for brain injury and aberrant neurodevelopment. Further research should seek the mechanisms for these associations, and finally evaluate the effectiveness of interventions targeting NSS in the assessment and treatment of these childhood conditions.