In recent years there has been much speculation about how events that occur during childhood can have a lasting impact on a child’s development. There have been many studies that attempt to look at how the impact of child stress affects different parts of development: physical development, psychological development, and social-emotional development. The purpose of this research was to observe and learn how stress affects emotional and social development and consequently impacts the child's risk for mental health issues. Although stress is a multidimensional concept and can be measured by biological responses, the presence of challenging environmental factors, and self-reports, for the purpose of this research stress was defined as the presence of adverse environmental factors. For development, I specifically observed attachment and emotional regulation. My focus on mental health was internalizing psychopathology, especially anxiety and depression. To gain a better understanding of the emotional social development of a child suffering from toxic stress, I looked at multiple studies already done that observed the effects of stress on a child’s social-emotional development. I also used conclusions drawn from experience gained while working at the Stress and Development Lab directed by Dr. Katie McLaughlin. For this approach I reviewed papers that demonstrated a connection between stress and mental health, between stress and development, and between development and mental health. I also looked for and identified factors that showed evidence of mitigating the effects of stress on mental health and development. These factors are referred to as protective factors. Identifying the aspects of development influenced by toxic stress and the mitigating factors is crucial to creating and implementing intervention techniques to promote healthy development and to decreasing the risk of internalizing psychopathology.