缩阳症（koro）或称恐缩症，是一种常见于中国和东南亚地区的文化结合症候群（Culture-bound syndrome）及心理疾病，患者即使其生殖器官没有任何真正的变化，仍会坚持他或她的生殖器官正在缩入体内，并且坚信其完全缩进人体就会致死，它被精神疾病诊断与统计手册所收录。此病全球都有发生记录，在非洲，亚洲和欧洲，与生殖器官收缩恐慌相关的集体歇斯底里有一定历史。在美国和欧洲，该综合症通常被称为生殖器后退综合症（genital retraction syndrome）。可通过心理评估以及身体检查，排除其他可能导致生殖器官缩入体内的疾病

Koro is a culture-specific syndrome in which an individual has an overpowering belief that his or her genitalia are retracting and will disappear, despite the lack of any true longstanding changes to the genitals. Koro is also known as shrinking penis, and it is listed in the Diagnostic and Statistical Manual of Mental Disorders. The syndrome occurs worldwide, and mass hysteria of genital-shrinkage anxiety has a history in Africa, Asia, and Europe. In the United States and Europe, the syndrome is commonly known as genital retraction syndrome. The condition can be diagnosed through psychological assessment along with physical examination to rule out genuine disorders of the genitalia that could be causing true retraction.