The neurodevelopmental continuum towards a neurodevelopmental gradient hypothesis

In contrast to the categorical approach of the current nosographic system, in the last decades increasing literature is suggesting that psychiatric disorders may be better conceptualized as a continuum, which would feature as a common basis a neurodevelopmental alteration. The “neurodevelopmental continuum” (NC) is a theoretical framework supported by several empirical evidences in multiple fields of research. The conceptual core of this model is that an alteration in brain development, the expression of which would be determined by the intertwined relationships between genetic and environmental factors, may constitute the common underpinning of different kinds of mental disorders. Moreover, the NC theory also implies that psychiatric conditions could be placed along a gradient, where autism spectrum disorder (ASD) with intellectual disabilities would be the most severe expression of an alteration of the “social brain development”, followed by other DSM-5 neurodevelopmental phenotypes characterized by a milder impairment. This model would subsequently include, along a decreasing neurodevelopmental gradient, other psychiatric conditions such as schizophrenia and mood disorders as well as eating and anxiety disorders, encompassing also non-psychopathological personality traits. From a cognitive point of view, the link between neurodevelopmental alterations and vulnerability towards psychopathology could be identified in an impairment of the proprioceptive experience and of the interoceptive inference, which would prevent the patient to properly define his own subjectivity and to adequately place him-self in the relational space. The conceptual framework proposed here may allow significant changes in both research and clinical settings, eventually leading to improve therapeutic and prevention strategies.