The papers of this thesis are not available in Munin due to publishers' restrictions: 1. Kummervold, P. E., Gammon, D., Bergvik, S., Johnsen, J. -A. K., Hasvold, T., & Rosenvinge, J. H.:'Social support in a wired world : Use of mental health forums in Norway', Nordic Journal of Psychiatry (2002), 56, 59-65. Available at http://dx.doi.org/10.1080/08039480252803945 2. Johnsen, J. -A. K., Rosenvinge, J. H., & Gammon, D.: 'Online group interaction and mental health : An analysis of three online discussion forums', Scandinavian Journal of Psychology (2002), 43, 445-449. Available at http://dx.doi.org/10.1111/1467-9450.00313 3. Johnsen, J. -A. K., Steinsvik, O. O., & Gammon, D.: 'Health-care professionals' participation in an online discussion forum : The impact on structure, content and interaction', Journal of Technology in Human Services (2003), 22, 31-44. Available at http://dx.doi.org/10.1300/J017v22n02_03 4. Johnsen, J. -A. K.: 'Constraints on message size in quasi-synchronous computer mediated communication : Effect on self-concept accessibility', Computers in Human Behavior (2007), 23, 2269-2284. Available at http://dx.doi.org/10.1016/j.chb.2006.03.006This project has focused on why and how people are using the Internet for healthissues. The studies involve collection of descriptive survey data aimed at determining the characteristics of the participants, what characterizes the use of online discussion forums for mental health, and the communication patterns of these forums. Based on these data the objective has been to establish an understanding of the needs this use fulfills for the participants, and the factors responsible for motivating and shaping behavior. Additionally, the impact of health-professionals’ involvement in these settings has been investigated, specifically how such involvement could affect the interaction patterns. Using theories from social psychology and social cognition, and evidence from laboratory research on text-based communication, a theoretical perspective is presented concerning people’s use of text-based, “poor” media in communicating about their health. Several methodological approaches are represented by the studies. The data presented in Paper I was collected by means of a web-based questionnaire that had participants enter the study by self-selection. The study was made possible by the cooperation of Doktor Online (DO; www.doktoronline.no) and Scandinavia Online (www.sol.no). Studies presented in Papers II and III were based on content analyses of log materials from the forums of DO. In Paper II content was condensed into categories to enable comparison of thematically different forums with regards to interaction patterns. Paper III investigated what effects health professionals would have on levels of social presence and interaction structure in an online health-forum. The two studies presented in Paper IV were laboratory experiments that challenge the view that text-based communication, as it is manifested on the Internet, are mainly different from face-to-face communication (speech) in terms of anonymity. This dissertation attempts to describe the relevance of these laboratory experiments in context of the health communication investigated in Papers I – III, and also outside of the online, selfhelp setting (i.e., traditional health-services). Electronically Mediated Health-Communication The results indicated that users of text-based communication for health-purposes were experiencing this as meaningful and rewarding. Participants exhibit high levels of selfdisclosure and share information with fellow participants that they would not share with others face-to-face. Furthermore, the communication patterns are believed to be potentially “health-promoting” by exemplifying social support, even in the absence of monitoring by health-professionals. It is argued that professional involvement might help facilitate discussions of special topics, for instance eating disorders. Participants view these forums as a supplement to traditional health-services, and they probably serve different functions. Also, it is argued that the characteristics of the communication medium (text-based) are likely to influence these behaviors and experiences markedly. These characteristics appear to influence people’s abilities to conduct strategic and controlled self-presentation, as measured by the accessibility of the “actual self” concept. This could help explain the health-related uses of text-based media and inform the design of future health services. Text-based health communication appears to fulfill important needs to those participating. These venues allow people to seek out information and find communion with their peers. In the process they disclosure highly personal information and provide and receive social support from others. Although these settings appear to be health promoting and serve a positive function in the lives of those participating, health professionals might have roles as moderators or role models in these settings. Clinical adaptations of these findings will extend these roles further. The experimental studies and the theoretical discussion provided by this thesis are advocating an approach to understanding individuals’ use of text-based communication technology for health-purposes along both interpersonal and intrapersonal dimensions based on theories of self-presentation and self-perception