Book excerpt: Epidemiology has been defined as the study of the distribution and determinants of health states or events in defined populations and its application to the control of health problems. Psychiatric epidemiology has continued to develop and apply these core principles in relation to mental health and mental disorders. This long-awaited second edition of Practical Psychiatric Epidemiology covers all of the considerable new developments in psychiatric epidemiology that have occurred since the first edition was published. It includes new content on key topics such as life course epidemiology, gene/environment interactions, bioethics, patient and public involvement in research, mixed methods research, new statistical methods, case registers, policy, and implementation. Looking to the future of this rapidly evolving scientific discipline and how it will to respond to the emerging opportunities and challenges posed by 'big data', new technologies, open science and globalisation, this new edition will continue to serve as an invaluable reference for clinicians in practice and in training. It will also be of interest to researchers in mental health and people studying or teaching psychiatric epidemiology at undergraduate or postgraduate level.