膨脹問題: 勃起缺乏 - 發病原因
膨脹問題可能有生理的或心理的發病原因。但是，就像在本教程中反復提及的那樣，這兩種發病原因的區分可能會引起誤解，因為這兩種類型的發病原因常常會以某種方式相互影響。由某些生理疾患所導致的勃起缺乏會不可避免地產生某些心理效應，而心理原因也會影響到一個男子的生理反應。簡而言之：性治療師在計畫對任何性功能障礙進行治療時，都應該始終要考慮到這兩種發病原因。

Problems of Tumescence: Lack of Erection - Causes
Tumescence problems can have physical or psychosocial causes. However, as repeatedly mentioned in this course, this distinction can be misleading, since very often both kinds of causes interact in some way. A lack of erection caused by some physical problem will unavoidably have some psychological effect, and psychological causes will also affect a man's physical response. In short: Therapists should always keep both of these aspects of any sexual dysfunctions in mind as they plan their course of treatment.