Chapter 11: Mood, Psychotic, Anxiety, and Obsessive-Compulsive Disorders: A Neuropsychiatric Foundation

INTRODUCTION

Contemporary neuropsychiatry conceptualizes mental illnesses as brain disorders. In contrast to neurological disorders with identifiable lesions, mental disorders can be addressed as disorders of brain circuits. The view of mental disorders as brain circuit disorders has been further consolidated by reports on successful treatment of mental disorders with focal brain interventions. However, mental illnesses not only originate from dysfunction of different brain areas but also represent a much more complex multidimensional organization of information in the brain. The basic biological science behind some of the fundamental elements of mental illness, such as cognition, emotion, behavior, and social processes, has been advancing rapidly in the past 20 years. New scientific methods for studying the brain include structural and functional imaging of distinct neural circuit elements and connections. Genetic techniques have identified risk factors for mental illness. Novel analytic techniques such as neural networks, a biologically inspired programming paradigm which enables learning from observational data, have partially revealed the basic neural mechanisms underlying mental illness.¹ However, clinical research supporting the classification system in psychiatry has not kept up with these scientific advances.^2,3 Psychiatric diagnoses are currently distinguished based on sets of specific symptoms as detailed in the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5), released in 2013.⁴ In 2009, the National Institute of Mental Health (NIMH) launched the research domain criteria (RDoC) project to develop, for research purposes, new ways of classifying mental disorders based on dimensions of observable behavior and neurobiological measures.⁵ Integration of clinical experience with the rapid advancing neurobiological knowledge is essential for every treatment provider in the field of psychiatry and neuropsychiatry.⁶

Genetic, neuroimaging, and clinical analyses find overlap across a wide variety of psychiatric diagnoses, suggesting common neurobiological substrates for mental illness. For example, a morphometry meta-analysis (n=15,892 individuals) across six diverse diagnostic groups (schizophrenia, bipolar disorder [BPD], depression, addiction, obsessive-compulsive disorder [OCD], and anxiety) found that gray matter loss converged across diagnoses in three regions: the dorsal anterior cingulate and right and left insula.⁷ Interestingly, the common neuroimaging findings in mental illness are related to cognitive functions. For example, abnormal activations in the left prefrontal cortex (PFC) and anterior insula, and the right ventrolateral PFC and intraparietal sulcus, demonstrate a common cognitive pattern of inflexibility across major psychiatric disorders.⁸ In most mental illnesses, cognitive impairment has a critical role in determining the total function and quality of life. Therefore, accurate assessment and treatment of the cognitive aspects of mental illness, not just emotional or behavioral symptoms, are an integral and important part of psychiatry.

While most psychiatrists are familiar with the dimensions related to mood, psychosis, or anxiety, it is important that they also know about other dimensions related to cognitive-behavioral and social neuroscience. The role of neuropsychiatry is expanding the field of psychiatry into these new dimensions and can provide advanced approaches to diagnosis, formulation, ...