Why is a high-density population stressful to the individuals?

A high-density population can be stressful to individuals because it can lead to overcrowding, competition for resources, and increased competition for mates. This can lead to increased stress levels, as individuals may feel overwhelmed by the number of people around them and the lack of resources available. Additionally, the increased competition for mates can lead to increased levels of aggression and competition, which can further increase stress levels.