Globalization has sparked international collaboration in our field, and this trend is expected to continue in the years to come. This offers excellent opportunities to learn more about the influence of children's sociocultural environments on their development and mental health. A particular challenge when studying risk factors across cultures and populations is that the risk associated with a particular exposure may depend on its prevalence: rarity tends to aggravate impact. This phenomenon complicates not only comparisons across cultures, but also those across subpopulations and time periods within a population. Moreover, it may counteract the effectiveness of risk-reducing public health efforts. On the bright side, the extent to which the impact of a risk factor is determined by its rarity provides researchers with valuable tools to deepen and sharpen theories about the nature and working mechanisms of that risk factor, with prevention and treatment strategies that also benefit youth in exceptional conditions as a likely consequence.