Four experiments tested the idea that social exclusion leads to (unintentionally) self-defeating behavior. Exclusion was manipulated by telling some people that they were likely to end up alone later in life. This randomly assigned feedback caused people to take irrational, self-defeating risks (Experiments 1 and 2), choose unhealthy, rather than healthy, behaviors (Experiment 3), and procrastinate longer with pleasurable activities rather than practicing for an upcoming test (Experiment 4). A control group, who heard that their future would be marred by frequent accidents, did not show these self-defeating patterns. Thus, the effect goes beyond just hearing bad news. Emotional distress did not significantly mediate these effects across 3 different mood measures. (PsycINFO Database Record (c) 2016 APA, all rights reserved)