Mental health problems are learning problems. Students seeking services at campus counseling centers are at increased risk of attrition. If the retention rate of college students seeking counseling center services is close to the retention rate of the overall student population, this is evidence of a significant positive effect for counseling services. If counseling center clients are retained at a higher rate than the overall campus population, this is evidence of a very large positive effect. A literature review identified five longitudinal studies that found that students seeking services at the campus counseling center had retention rates significantly higher than an appropriate control group. In addition, counseling center surveys consistently find that about two thirds of their clients report that counseling services helped them stay in school. Collectively, this data provides strong evidence that counseling services have a significant positive effect on retention, and should be included on lists of high impact practices.