Human development reportedly includes critical and sensitive periods during which environmental stressors can affect traits that persist throughout life. Controversy remains over which of these periods provides an opportunity for such stressors to affect health and longevity. The elaboration of reproductive biology and its behavioral sequelae during adolescence suggests such a sensitive period, particularly among males. We test the hypothesis that life expectancy at age 20 among males exposed to life-threatening stressors during early adolescence will fall below that among other males. We apply time-series methods to cohort mortality data in France between 1816 and 1919, England and Wales between 1841 and 1919, and Sweden between 1861 and 1919. Our results indicate an inverse association between cohort death rates at ages 10-14 and cohort life expectancy at age 20. Our findings imply that better-informed and more strategic management of the stressors encountered by early adolescents may improve population health.