The initial causes of shyness vary. Scientists have located some genetic data that supports the hypothesis that shyness is at least partially genetic. However, there is also evidence that the environment in which a person is raised can affect their shyness. Shyness can originate after a person has experienced a physical anxiety reaction; at other times, shyness seems to develop first and then later causes physical symptoms of anxiety.

Shyness differs from social anxiety, which is a broader, often depression-related psychological condition including the experience of fear, apprehension or worry regarding social situations and being evaluated by others to panic-inducing extents.