In a process as complex as penile erections, problems can occur for many reasons. Very often an erectile problem will have more than one cause. The causes may be physical (organic ED), psychological (psychogenic ED), or a combination of both. Distinguishing between physical and psychological causes is helpful, because treatments may differ depending on the cause.
Organic Erectile Dysfunction
The most common cause of organic erectile dysfunction is vascular (blood vessel) disease. Vascular diseases may cause problems with blood flow into the penis to make it erect, or problems with trapping of blood within the penis to maintain the erection. Atherosclerosis (buildup of plaque within the walls of arteries) is the cause of approximately 40% of erectile dysfunction in men older than 50. Among the most commonly recognized conditions associated with atherosclerosis are high blood pressure, lipid problems (cholesterol, triglycerides), diabetes, and cigarette smoking.
Diseases that affect the nervous system, such as multiple sclerosis, Parkinson's disease, and Alzheimer's disease can also cause erectile dysfunction. Some diseases associated with erectile dysfunction affect both the vascular and nervous systems. Diabetes is an example. In patients with diabetes mellitus, irrespective of type, the prevalence of erectile dysfunction is approximately 50% (range 20 to 75%) with the prevalence dependent on patient age, duration of diabetes and severity of the diabetes.
Endocrine disorders, such as low testosterone and thyroid problems, may be associated with ED. These disorders can also affect sexual desire and cause various other symptoms.
Erectile dysfunction can result from pelvic fractures or crush injuries experienced in an automobile, motorcycle, or other accident. The accident victim may be left with injured nerves and/or penile arteries that cannot supply enough blood to the penis to provide an erection. Spinal cord injuries that destroy nerve fibers are another cause of erectile dysfunction. Some types of surgery and radiation therapy, such as those for treating prostate, bladder or rectal cancer, also carry a risk of erectile dysfunction.
Other chronic disease states associated with a high prevalence of erectile dysfunction include chronic kidney failure, liver failure, sleep apnea, and chronic obstructive pulmonary disease (COPD).
The effects of aging on erectile function have also been studied. Although the rate of erectile dysfunction in the male population increases with age, aging itself does not appear to be the cause. It appears that disease processes such as vascular diseases and diabetes, which may develop as a man ages, are the cause of erectile dysfunction with aging. There may be contributing effects, as well, from years of smoking or alcohol abuse.
Many medications, including certain blood pressure pills, cold medications, hormones, antidepressants, tranquilizers, alcohol, tobacco, heroin, and cocaine, are associated with erectile dysfunction.
Psychogenic Erectile Dysfunction
Psychological causes of erectile dysfunction (Psychogenic ED) include stress and anxiety due to marital, financial or other personal problems. It is possible for a man's stress and anxiety to interfere with nerve impulses from his brain when he attempts sexual intercourse. "Performance anxiety" is also a common cause of erectile dysfunction. Because of anxiety about his ability to "perform," a man finds he cannot perform - which causes more anxiety, thus completing a vicious cycle. Psychiatric illnesses such as depression can also cause erectile dysfunction.
It is believed that a portion of men who have organic ED develop psychogenic ED as a result of their anxiety and lack of confidence related to sexual performance.