A sexual dysfunction whereby a man cannot get or maintain an erection sufficient for satisfactory sexual performance. Commonly referred to as ED or impotence, it can be caused by several different factors such as cardiovascular disease, diabetes, neurological disorders, depression, performance anxiety, stress, low hormone levels, and use of alcohol or drugs. Most men will experience ED at least once in their lives, but medical treatment is not necessary unless it occurs more than 50% of the time or causes significant relationship problems.