Wikipedia
Co-rumination is a relatively new construct, referring to extensively discussing and revisiting problems, speculating about problems, and focusing on negative feelings with peers. Although it is similar to self-disclosure in that it involves revealing and discussing a problem, it is more focused on the problems themselves and thus can be maladaptive. While self-disclosure is seen as a positive aspect found in close friendships, some types of self-disclosure can also be maladaptive. Co-rumination is a type of behavior that is positively correlated with both rumination and self-disclosure and has been linked to a history of anxiety because co-ruminating may exacerbate worries about whether problems will be resolved, about negative consequences of problems, and depressive diagnoses due to the consistent negative focus on troubling topics, instead of problem-solving. However, co-rumination is also closely associated with high-quality friendships and closeness.