We investigate the causal impact of jail mental health needs scores, assigned by clinicians, on youth and adult outcomes. Utilizing an instrumental variable (IV) approach leveraging quasirandom assignment of intake clinicians, we find that worse scores increase incarceration duration and suicide attempts in both groups and recidivism in adults. For the marginal person, worse scores may lead to consequences like prolonged jail stays, which counteract potential benefits. We discuss possible mechanisms, including the existence of a mental health docket for misdemeanors, and effects of scores on bond posting, mental healthcare, type of housing within the jail, and length of stay.