While there has been a lot of debate over the impact of online and remote learning on mental health and well-being, there has been no systematic syntheses or reviews of the research on this particular issue. In this paper, we review the research on the relationship between mental health/well-being and online or remote learning. Our review shows that little scholarship existed prior to 2020 with most studies conducted during the COVID-19 pandemic. We report four findings: (1) pandemic effects are not well-controlled in most studies; (2) studies present a very mixed picture, with variability around how mental health and well-being are measured and how/whether any causal inferences are made in relation to online and remote learning, (3) there are some indications that certain populations of students may struggle more in an online context, and (4) research that does not assume a direct relationship between mental health and online provides the best insight into both confounding factors and possible strategies to address mental health concerns. Our review shows that 75.5% of published research on this topic either commits the correlation does not equal causation error or asserts a causal relationship even when it fails to establish correlations. Based on this study, we suggest that researchers, policymakers, practitioners, and administrators exercise extreme caution around making generalizable assertions with respect to the impacts of online/remote learning and mental health. We encourage further research to better understand effects on specific learner sub-populations and on course—and institution—level strategies to support mental health.