They have a condition called social anxiety disorder, also known as social phobia. The condition has been officially recognized as a psychiatric disorder since 1980. Shyness is not a mental illness. It is a personality trait that affects how people interact with others. Shy people may feel uncomfortable in social situations, and may need more time to warm up to people. There is no single cause for shyness, but it may be due to a combination of genetic and environmental factors. Shyness can be treated with therapy and/or medication.