This book is about public mental health needs and aspects of substance use disorders in South Asian countries. South Asia consists of eight countries with low- and middle-income backgrounds. The people of this region, with a combined population of around 2 billion, share common cultures, beliefs, and behavioral patterns regarding physical and mental health. Among them, more than 66 million people use different forms of substances including cannabis, opium and opiates, amphetamine, and prescription drugs. Substance abuse brings deadly consequences. It affects almost all spheres of life, i.e., personal, social, recreational, criminal, and family aspects; both physical and mental health; and economy of the society as well as the country. Advanced management and holistic prevention are public health priorities. However, very little attention has been paid to the issues as a region as well as in countries like Afghanistan, Bangladesh, and Pakistan. Hence, the editors of this book aimed to publish a book that discusses the public mental health and healthcare issues related to substance use disorder in a densely populated low- and middle-income setting.