Social media, big data, and mental health: current advances and ethical implications

•Mental health is the fifth greatest contributor to the global burden of disease.•Population mental health systems require strengthening to address this need.•Social media big data combined with NLP can address public health research questions.

Mental health (including substance abuse) is the fifth greatest contributor to the global burden of disease, with an economic cost estimated to be US $2.5 trillion in 2010, and expected to double by 2030. Developing information systems to support and strengthen population-level mental health monitoring forms a core part of the World Health Organization's Comprehensive Action Plan 2013–2020. In this paper, we review recent work that utilizes social media ‘big data’ in conjunction with associated technologies like natural language processing and machine learning to address pressing problems in population-level mental health surveillance and research, focusing both on technological advances and core ethical challenges.