Adverse childhood experiences (ACEs) are distressing experiences that have significant and lasting effects on an individual’s mental health. This chapter systematically reviews the literature on the relationship between childhood experiences and the development of mental health problems across the lifespan. A structured methodology was developed on the basis of PRISMA guidelines, and studies published between 2013 and 2023 were identified from the Scopus and Pub Med databases. The studies included in the chapter highlight a greater risk of depression, anxiety, behavioral problems, substance abuse, and suicidality when correlated with ACEs. This chapter reveals significant geographical and methodological gaps in the literature. Furthermore, the findings underline the importance of early intervention, a supportive environment, and preventive strategies to mitigate the impact of childhood adversity.