“Transhood” is fixated on transition, and therefore preoccupied with time, or at least that seems to be its intention. The HBO documentary, which follows four transgender and gender-nonconforming children in Kansas City, Mo., over five years, races through their changing and evolving understanding of themselves, with barely a moment to catch its breath.
Many scenes are fleeting and shorn of a more contemplative approach not only to transgender identity, but also to childhood more broadly.