Density is one of the advantages of a city. It is the infrastructural prerequisite for cooperation, distribution of responsibilities and efficiency that differentiates urban spaces areas from rural areas. However, social density in particular can also lead to social stress and thus become relevant to human health. Consequently, from a neurourbanistic perspective, density is an ambivalent topic. If density leads to a lack of space and overcrowding, it puts a strain on almost everyone. This phenomenon, which can be traced back to an innate sensitivity that can also be observed in animals, is known as ‘crowding stress syndrome’. High density leads to negative consequences such as withdrawal, reduction of mating readiness and fertility, as well as a weakening of the immune system. In humans, social density primarily has negative consequences when the individual loses control over the living environment (environmental mastery) and feels unable to influence it. Persistent exposure to social density combined with low environmental mastery can lead to chronic stress and consequently to psychological stress, behavioural changes, disorders and even premature mortality.