People facing serious health threats increasingly use Internet health support communities to obtain informational support, emotional support and other resources. This study introduces software algorithms similar to those used by social media sites to put people in touch with helpful information and social interactions. Participants from the American Cancer Society's Cancer Support Network will have access to this online support group using the default interface that orders content by broad content category and date or with a new interface that highlights communication content and people that match users' interests and needs.

Internet support groups (ISGs) are online communities where people come together to exchange information, emotional support and other resources. They are an important resource for patients grappling with serious medical conditions. Although participation in health-related ISGs has been associated with significant reductions in participant-reported depression, anxiety and other indicators of psychological distress, many ISG members leave too soon to benefit. In a parallel study, we are using state-of-the art machine learning and automated language analysis techniques to assess the types of interactions that keep people participating in these groups and that lead to improved psychosocial well-being and health quality of life and how these interactions develop. The clinical trial described here uses these technologies and insights from our empirical research to build, deploy, and evaluate interventions that improve the interactions in Internet health support groups.

We will develop and pilot-test interventions to encourage effective communication processes identified in our empirical research. Participants from the American Cancer Society's Cancer Support Network will access this support group using either the default interface that orders content by disease diagnosis and date or with a new interface that sometimes highlights communication content and people who match their interests and needs. We will test whether mood, satisfaction with interactions and engagement in the group increase following interventions that (a) increase participants' receipt of individualized support from others; (b) provide participants with opportunities to offer support to others; (c) facilitate participants' expression of emotions; and (d) help participants form relationships with compatible peers. In a series of small, randomized experiments, we will examine how these interventions affect participants' communication behaviors as well as short-term engagement and satisfaction with their online interactions.

Inclusion Criteria:

• Is an existing or new registrant to the American Cancer Society's Cancer Support Network.

Exclusion Criteria:

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