Gamification, the use of game elements in non-game settings, is more and more used in education to increase learner motivation, engagement, and performance. Recent research in the gamification field suggests that to be effective, the game elements should be tailored to learners. In this paper, we perform an in-depth literature review on adaptive gamification in education in order to provide a synthesis of current trends and developments in this field. Our literature review addresses 3 research questions: (1) What are the current kinds of contributions to the field? (2) What do the current contributions base their adaptation on, and what is the effect of this adaptation on the gamified system? (3) What is the impact of the adaptive gamification, and how is this impact measured? We also provide future research guidelines in the form of three needs that should be fulfilled for exploring this field.