
Erectile dysfunction (ED) is the inability to achieve or maintain an erection sufficient to permit satisfactory sexual intercourse.1
Some experts suggest "consistent inability" to be part of the definition because most men experience transient episodes of ED that are temporary and usually associated with fatigue, depression or other stressful emotions, which is also referred to psychogenic ED. A period of persistence for longer than 3 months has been suggested as a reasonable clinical guideline, especially when anatomical causes are prominent which could be referred to organic ED.
Reference:
1. NIH Consensus Conference. "NIH Consensus Development Panel on Impotence." Journal of the American Medical Association: 270 (1993): 83-90.