When competent adults are treated like children, negative outcomes sometimes follow. We used a concurrent study design to conduct an internet-based study to determine how infantilization varies by demographic category and which types of infantilization might be most harmful. The test, which measured 15 types of infantilization, was taken by 32,118 people (mean age 27.6) from 153 countries (most from the United States). Test scores were correlated with self-reported happiness, depression, anger, sense of control, and personal and professional success, and regression analyses consistently showed that of the 15 types of infantilization we measured, emotional abuse was by far the best predictor of adverse outcomes. Infantilization was highest during the teen years and decreased gradually throughout adulthood. Effects were found for gender, education, and sexual orientation, with vulnerable groups more subject to infantilization. Our data, collected between 2011 and 2020, appear to parallel recent increases in authoritarianism and intolerance, with total infantilization scores increasing by 30.1% over this period.