Researchers have proposed a variety of mechanisms through which playing video games might affect mental health: by displacing more psychosocially beneficial activities, satisfying or frustrating basic psychological needs, relieving stress, and many more. However, these mechanisms are rarely enumerated, and underlying causal structures are rarely made explicit. Here, we overview 13 proposed effects of gaming on mental health. For each, we attempt to draw out (often implicit) counterfactuals—that is, what concrete aspect of gaming should be changed in a hypothetical alternative universe to produce the effect of interest—and illustrate these with example directed acyclic graphs (DAGs). In doing so, we hope to provide a bird’s eye view of the field and encourage more focused and collaborative efforts to propose, falsify, and iterate on (causal) theories. Only in doing so can the field realize its potential to inform clinical interventions, regulation, game design, and the behavior of players and parents.