Online mental health communities provide spaces for individuals with mental health issues to receive social support. However, such interaction has a dark side since giving back social support may result in social overload. By employing social support theory and social overload theory, we frame these concepts within the online context. Our study with 110 online mental health community members revealed that social support and social overload do not directly interact; instead, social overload arises only when social support translates into supportive behavior. Additionally, we expand previous research by highlighting that community cohesiveness and a sense of universality are crucial in determining social support for members. We propose that individuals within online mental health communities first need to establish a certain safe space before they become active themselves.