Humans fail to understand the world around them and also fail to recognize this lack of understanding. The illusion of explanatory depth (IOED) exemplifies these failures: people believe they understand the world more deeply than they actually do and only realize that this belief is an illusion when they attempt to explain elements of the world. An unexplored factor of the IOED is how people may become overconfident by confusing their own understanding with others’ understanding. In two experiments, we examine the IOED in mental disorders, a domain where society has a limited understanding. In Experiment 1, we demonstrate that people display an IOED for mental disorders as well as devices, but that it is smaller for mental disorders. In Experiment 2, we show that exposing the IOED is specifically linked to generating an explanation, rather than more generally thinking about a phenomenon.