Understanding how individuals and groups perceive their surroundings and how different physical and social environments may influence their state-of-mind has intrigued re-searchers for some time. Much of this research has focused on investigating  why certain natural and human-built places can engender specific emotive responses  (e.g. fear, disgust, joy, etc.) and, by extension, how these responses can be considered in placemaking activities such as urban planning and design. Developing a better understanding of the linkages between place and emotional state is challenging in part because both cognitive processes and the concept of place are complex, dynamic  and multi-faceted and are mediated by a  confluence of contextual, individual and social processes. There is evidence to suggest that social media data produced by individuals in situ and in near real-time may provide novel insights into the nature and dynamics of individuals’ responses  to their surroundings. The explosion  of user-generated digital data and the sensorization of environments, especially in urban settings, provide opportunities to build knowledge of place and state-of-mind linkages that will inform the design and promotion of vibrant placemaking by individuals and communities. In this paper we present a novel study, to be undertaken  this summer within the Greater Toronto  area in Canada, with 140 recruited participants who are frequent, geo-tagging, Twitter users. The goal of the study will be to assess emotional, acute and chronic stress experienced in urban built-environments and as expressed during  daily activities. An existing automated semantic natural language processing tool will be validated through this study, and it is hoped that the methodology developed can be extrapolated to other urban environments as well, with a second validation study already planned to take place next year in London, United Kingdom.