There's an ideology out there affecting boys and men, and the American Psychological Association says it's "harmful." The Los Angeles Times reports on the APA's first official warning on the toxicity of "traditional masculinity," which "has been shown to limit males' psychological development, constrain their behavior, result in gender role strain and gender role conflict and negatively influence mental health and physical health." Featured this month in the APA's Monitor on Psychology magazine, the "APA Guidelines for the Psychological Practice with Boys and Men"—a 13-year effort that involved scientists poring over more than four decades of research—notes the harmful effects tied to traditionally masculine traits, including being competitive, aggressive, and stoic.

The APA offers some stats to back up its claim: Men in the US, for instance, commit 90% more homicides than women.

Also holding sway "over large segments of the population" are such traits as "anti-femininity, achievement, eschewal of the appearance of weakness, and adventure, risk, and violence." The report notes that by males conforming to these traits, they may bury their feelings and pretend things are OK when they're not, which could, down the line, lead to sexual harassment, homophobia, and violence.

The Atlanta Journal-Constitution notes that, per the study, men show disproportionate rates of substance abuse, cardiovascular issues, early mortality, and quality-of-life problems, among others, yet tend to not seek needed help—and even when they do, many say their male-related issues aren't addressed.

Not that the APA thinks every single aspect of traditional masculinity is harmful: Leadership and courage, for example, are positive traits boys and men should strive toward, the group says.

(A study has tied manliness to depression.)

This article originally appeared on Newser: Psychologists Warn About 'Traditional Masculinity'