The incidence of which mental disorder peaks around age 21, with men being more likely to develop it than women?

The correct answer is associated with schizophrenia, which typically begins to manifest in late adolescence to early adulthood, with a peak incidence around age 21. Research indicates that men are more likely to develop schizophrenia than women, often presenting symptoms earlier in life. This aligns with the recognized pattern in the onset of the disorder, where males tend to experience earlier onset than females, with the latter typically showing symptoms a few years later.

In contrast, major depressive disorder and anxiety disorders can occur at various stages throughout life, with no specific peak incidence exclusively at age 21. While bipolar disorder does have episodes that can emerge in adolescence or young adulthood, the distinction in peak incidence compared to schizophrenia supports that schizophrenia is the most fitting answer to the question posed.