Previous reviews of research conclude that, overall, adolescents’ religiosity is linked with many positive individual and social outcomes. Only negative forms of religion would imply negative outcomes. In the present chapter, such a conclusion is importantly nuanced. I systematically review here previous studies and present new data on the relation between religiosity (major forms of it) and key aspects of adolescents’ social development: personality, values, identity status, and collective (ethnic and immigrants’ new) identities. Attention is paid to provide cross-cultural information, when available. In addition, I present a new study integrating the cognitive, emotional, personality, and moral factors involved with religious doubting in adolescence. Consistently across studies and domains of social development, the findings are in favor of the “coherence at the detriment of openness” hypothesis. Adolescent religion seems to reflect stability, conservation, engagement, and cohesion, but potentially somehow at the detriment of plasticity, openness, exploration, and autonomy – all important for optimal development. Complementing others’ argument that adolescence is a “sensitive” period for spiritual development, I argue that adolescence is also a “sensitive” period for religious doubting and agnosticism.