High blood pressure affects nearly one third of all people in the United States. It can be caused by many factors, including obesity, sodium intake, genetics, and stress. Ethnicity appears to also play a role, because African Americans are more susceptible to developing high blood pressure than other ethnic groups, with more than 40% of African Americans diagnosed with this condition. This study will examine the underlying reasons of why stress and African-American ethnicity contribute to high blood pressure risk and how ethnicity and stress interact with each other to increase this risk. Specifically, study researchers will examine how stress increases blood pressure, how people from different ethnic groups respond to stress differently, and how sleep plays a role in regulating blood pressure levels.