A recent survey estimates that more than 40 million Americans ages 12 and older met the criteria for substance use disorders (SUDs) in the past year. Yet few FDA-approved treatments exist for SUDs, and no explicit treatment guidelines. In the case of multi-SUDs, the literature is particularly scant. It is in response to this gap in knowledge that this volume has been developed, grounded in the clinical experience of the addiction psychiatrists who have contributed their knowledge. In accessible, easily referenced chapters, dedicated mental health clinicians and primary care clinicians alike will find actionable information on the neurobiology of addiction, general approaches to taking a history, guidelines for making medical and psychiatric evaluations and forming a diagnosis, and discussion of the pharmacological treatment of a range of substances. Uniquely, this guide also discusses psychopharmacological approaches to working with special patient populations―such as pregnant people, LGBTQ+ individuals, and adolescents―so that, no matter the patient's background, providers can effectively aid them in their recovery journey.