Background: Online support groups (OSGs) are often a convenient way for many patients with cancer and cancer survivors to obtain information and support. However, not all OSGs are helpful, and in some cases, they may increase distress. Overall, there is a lack of clear evidence on the effects of OSGs, along with how and why they work.
Objective: This study examined how, for whom, and in what contexts OSGs work for patients with cancer and cancer survivors.
Methods: A realist review of the evidence on cancer OSGs was conducted (12 databases, inception to 01/10/2025). Realist reviews examine how underlying causal processes of an intervention (mechanisms) in specific circumstances (contexts) interact to produce results (outcomes). A program theory (e.g. conceptual framework) was developed to explain how cancer OSGs work.
Results: Of 16,659 articles identified, 168 were included. Cancer OSGs can be an effective tool for providing emotional, informational, validatory, and altruistic support. This can lead to changes in distress, isolation, empowerment, and self-esteem, through negative and positive appraisals as well as coping efforts. These outcomes, however, depend on user attitudes about OSGs, how well the OSG fits their needs, and perceptions of control (i.e., availability, privacy, anonymity). If an OSG was a good fit for a user’s needs (e.g., relevant and relatable), whether they experienced positive outcomes or not depended on features of the communication technology (i.e., response time, visual cues), group dynamics (i.e., norms, moderation, connectedness), and content (i.e., emotional expression, cognitive processing).
Conclusions: OSGs can address supportive care needs and improve psychosocial wellbeing for patients with cancer and cancer survivors. However, outcomes depend on specific contexts and mechanisms that impact how well OSGs meet patients’ needs. To optimize effectiveness of OSGs, we recommend (1) helping to assess fit and address specific needs; (2) demonstrating trustworthiness; (3) enhancing anonymity and control, and protecting privacy; (4) enhancing ease of use; (5) supporting connection and belonging; (6) encouraging activity; (7) enhancing the nature of content shared to boost therapeutic effects; and (8) monitoring and adjusting design and management strategies to enhance effectiveness.