Schizophrenia Spectrum Disorders (SSD) manifest multidimensionally, presenting a syndromic nature with several symptomatic domains. These are driven by dynamic systemic biological changes that unfold over the course of the disease. Thus far, the diagnosis is solely based on symptoms, which may be rather subjective, moving research toward the search for SSD biomarkers. This book presents a summary of the main hypotheses that have evolved over time to explain the pathophysiology of SSD and that have driven the discovery of associated biomarkers: neurotrophic, neurotransmitter,...