According to the biological perspective, generalized anxiety disorder is

According to the biological perspective, generalized anxiety disorder is:  linked to an imbalance in several neurotransmitters in the nervous system

For example, when a normal person's perceive a stranger as a potential friend or simply someone with no impact on their lives, the brain of the people with anxiety disorder will tell them that the stranger is a threat for them 

Urban growth invariably feeds increased commercialization and industrialization. it requires continually expanding land areas. when urbanization rates are high, and countries do not have the institutional and managerial capacities or economic wherewithal to manage such rapid growths, they exert intense pressure on the types and nature of the resulting settlements. they contribute to the development of overcrowded slums and shanty towns without adequate essential services and necessary infrastructure.-by asit k. biswas and cecilia tortajada