膨脹問題: 缺乏勃起 - 社會心理原因
業已證明，當我們討論缺乏勃起或勃起不堅的非生理發病原因時，把這種發病原因導致的缺乏勃起區分為原發性和繼發性缺乏勃起是比較適用的。當面對一個性伴從未有過勃起，這就叫原發性缺乏勃起；如果面對一個性伴過去曾經有過勃起，但現在勃起缺乏，稱繼發性缺乏勃起。這兩種類型的缺乏勃起通常起因是完全不同的，所以需要不同的治療方法。

Problems of Tumescence: Lack of Erection - Psychosocial Causes
When discussing non-physical causes of weak or absent erections, it has proved useful to distinguish between primary and secondary problems of tumescence. We speak of primary problems when a man has never had an erection in the presence of a partner; we speak of secondary problems if he has had erections in the past. The two cases are usually quite different in origin and require different treatments.