Chapter “Depression in the Emergency Department” is available open access under a Creative Commons Attribution 4.0 International License via link.springer.com. This fully updated second edition focuses on mental illness, both globally and in terms of specific mental-health-related visits encountered in emergency department settings, and provides practical input from physicians experienced with adult emergency psychiatric patients. It covers the pre-hospital setting and advising on evidence-based practice; from collaborating with psychiatric colleagues to establishing a psychiatric service in your emergency department. Potential dilemmas when treating pregnant, geriatric or homeless patients with mental illness are discussed in detail, along with the more challenging behavioral diagnoses such as substance abuse, factitious and personality disorders, delirium, dementia, and PTSD. The new edition of Behavioral Emergencies for Healthcare Providers will be an invaluable resource for psychiatrists, psychologists, psychiatric and emergency department nurses, trainee and experienced emergency physicians, and other mental health workers.