Diet, Immune System, and Psychiatric Disorders

Accumulating evidence suggests that inflammation plays an important role in the pathophysiology and therapeutic mechanism across major psychiatric disorders. “Inflammation theory” might not be the full answer for the big picture of mental disorders, but it might explain the high occurrence of somatic symptoms and comorbidity of physical illness in certain subtypes of the heterogeneous groups. Nutritional psychiatric research has been expanding in the past two decades. Epidemiological studies showed that nutritional deficiency has been associated with an increased prevalence of psychiatric disorders, while nutritional supplementation has been shown to reduce or even play a role in the prevention of psychiatric disorders. Moreover, inflammatory regulation has been suggested to be the possible link between nutritional supplementation and psychiatric disorders. Thus, the aim of this chapter is to discuss the role of nutritional supplementations, including omega-3 polyunsaturated fatty acids (n-3 PUFAs) and prebiotics/probiotics, in two commonly seen psychiatric disorders, major depressive disorder (MDD) and attention deficit hyperactivity disorder (ADHD), with inflammatory regulation as the shared mechanism.