Although panic disorder may mimic medical conditions, patients with medical conditions that seem to pose a real life threat may be diagnosed when panic attacks, which are not well explained by any existing disease, repeatedly appear. After they accept the idea of possessing panic disorder, the most commonly asked question by patients is what has caused this condition. For the author, with more than 20 years of clinical experience, it is not easy to satisfy patients with simple answers. An exemplary explanation may be that the combination of heredity, environment, genetic-environmental interactions, neurotransmitters, the HPA axis, and any forms of stress affects the onset of panic disorder. Genetic susceptibility obviously affects panic disorder, but does not account for up to 30-40% of occurrences. Stressful life events often precede the onset and seem to increase the risk of panic disorder development, but not in all cases. In fact, the cause of panic disorder is still unknown. However, step-by-step approaches toward understanding the causes and developing new treatments for panic disorder through research on the epidemiological studies, genetics, epigenetic studies, neuroimaging studies, and studies dissecting neural circuits for regulating normal fear and anxiety are being put into effect. The latest advances in therapy for treatment-resistant patients who do not respond well to therapy have been addressed in this book. This book is the result of a worldwide collaboration of experts who are outstanding in the research of panic disorder. The author hopes that this book will give patients, clinicians, and clinical researchers the latest insights into panic disorder.