This book aims at providing the reader with an introduction to psychiatry and to the study of mental disorders. While still addressing basic theoretical concepts of importance for the understanding of psychiatry as a specific field of knowledge, its main focus is not an extensive discussion or a comprehensive review of research findings. Instead, whenever possible, the different topics are addressed from a practical point of view, allowing the reader not only to expand their base knowledge but, most importantly, to obtain a good picture of how patients experiencing these conditions usually present themselves in clinical contexts. Moreover, the treatment of mental disorders is addressed in an objective, straightforward way, based on the respective authors’ own clinical experience in the management of a high number of patients, in different settings.

Bipolar disorder (BD) is one of the most important and potentially incapacitating mental disorders, typically characterized by the alternation of depressive symptoms with periods of elevated mood, called manic or hypomanic episodes. The present chapter provides an overview of the main aspect of this psychiatric condition, including its clinical presentation, diagnosis, pathophysiology, and therapeutic aspects. While the diagnosis and management of BD can be challenging, ongoing research has led to considerable advances in its understanding. It is expected that those advances will bring about improvements in the identification and treatment of this mental illness.

Over the past few decades, the role of inflammation in the pathophysiology of depressive disorder and bipolar disorder has been the focus of considerable attention. In this chapter, we provide an update on the association between inflammatory processes and mood disorders, in light of available evidence. The pathophysiological and clinical implications of this association are critically discussed, as well as the interaction between inflammation, metabolic abnormalities, and medical comorbidities, which have important prognostic consequences for patients with mood disorders.

Mood disorders are among the most prevalent and potentially severe mental disorders. These conditions are associated with important psychological morbidity and functional impact, as well as elevated rates of suicide. While the past several decades have produced valuable contributions to the understanding of the pathophysiology of mood disorders, currently available treatments at times fail to produce full remission and restore patient’s premorbid level of function. Nevertheless, promising new agents and novel therapeutic targets are currently under investigation. The twenty-first century is looking at an individualized approach for the management of mood disorders, with the proper integration of evidence-based, effective biological and psychosocial therapeutic modalities.

There is no consensus for the concept of treatment-resistant depression (TRD). Although some authors argue considering TRD a depression subtype is not supported by evidence, its impact on the individual and society is clear. This chapter discusses the concept of TRD, presents evidence about its neurobiology, pharmacological interventions, and describes drugs currently under investigation. Among the pharmacological strategies to manage TRD, guidelines include increasing the antidepressant dose, switching to another new antidepressant, combining two or more antidepressants, and augmentation of the current medication. Several new components have been investigated for TRD targeting, for instance, the glutamatergic system, inflammatory system, the opioid system, the cholinergic system, dopaminergic system, and neurotrophin signaling. Finally, machine-learning techniques using clinical and neurobiological data provide promising information about treatment outcomes prediction that could change the current approach to a more personalized one.