Improving health outcomes for concussed athletes and others requires self-reporting symptoms; not reporting risks second-impact syndrome and death. However, concussions in adolescents and young adults are often underreported. We treat reporting as a risky decision, extending predictions of fuzzy-trace theory (FTT). We hypothesize that low SES indirectly interferes with the development of cognitive skills that reduce unhealthy risky decision making. Specifically, we expect that SES may be related to intentions to report a concussion because low SES delays development of cognitive gist processing that reduces risk-taking. Adolescents in high-school and young adults in college (n = 1211) answered questions about concussion knowledge, concussion attitudes, and cognitive scales based on FTT: categorical thinking and endorsement of gist principles about risk. Overall, for each of the two age groups, and for athletes as well as nonathletes, SES was associated with reporting intentions, and this association was mediated by the three psychological predictors we tested: gist processing, concussion knowledge, and concussion attitudes. Results are consistent with lower SES reducing opportunities for normative cognitive development, the latter characterized by developmental increases in gist processing about risk. Hence, consistent with hypotheses, gist processing, concussion knowledge, and healthier attitudes about concussions were each associated with greater intentions to report concussions. Although educational initiatives currently focus on rote knowledge and healthy attitudes, future interventions to reduce concussion underreporting could benefit from explaining the gist of risk, especially to low SES youth, adapting successful FTT-based risk-reduction curricula from other domains.