Mental health issues are one of the most common illnesses. Thus, in the last years, mental health has become a more prominent problem domain in NLP. In this interdisciplinary research, human language is examined as a tool to better understand emotional and mental states to reduce the emotional suffering. The research directions are manifold. They range from the detection of mental illnesses or suicide risk in social media, the analysis of psychiatric or psycho-therapeutical dialogues, to the development of online therapeutic dialogue systems.