Psychogenic factors including depression are common causes of ED. About 25–75% of patients with depression experience some degree of ED. Cigarette smoking and alcohol have a negative impact on penile blood flow as well as on the nerve supply. Cigarette smoking appears to cause a constriction of small penile arteries.
More than 30% of cases of ED are estimated to correlate with a comorbid illness. Pathologic causes of ED include the following:
• Vascular disease, ^40%
• Diabetes mellitus, ^20%
• Severe dyslipidemia, ~10%
• Medications, >5%
• Endocrine, ^5%
• Urologic, ^5%
• Neurologic, <2%
• Other, ~13%: renal and hepatic failure, HIV infection, all forms of cancer.
A. Cardiovascular Disease
In epidemiologic studies hypertension, coronary artery disease, and peripheral vascular disease are frequently associated with ED. Approximately 75% of men with coronary artery disease have ED with the condition severe in greater than 25%. Several studies support the associa¬tion between ED and coronary artery disease and correlate coronary disease with difficulty in achieving erections. In some, the onset of ED predated the symptoms and dia¬gnoses of coronary disease by a few months to a year.
Men with two- or three-vessel obstructive coronary artery disease were observed to have significantly fewer erections during a 30-day period and scored lower on an index of erection firmness than men with single-vessel disease. In a study of 50 men with ED of presumed vascular origin, multiple risk factors were present in 80%, smoking in 80%, and elevated total cholesterol greater than 200 mg/dl (5.2 mmol/L) in 70%. Coronary angio¬grams in 20 of these individuals showed significant coronary artery obstructive lesions: severe left main or three-vessel disease in 6, two-vessel disease in 7, and single-vessel disease in 7, and graded exercise testing was positive in 28 (56%) of these subjects.

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