The Causes of Male ED

Erectile dysfunction occurs when the physical or psychological processes responsible for achieving an erection are disrupted. Approximately 18 million men over the age of 20 are affected by erectile dysfunction in the United States alone, according to a study conducted by the Johns Hopkins Bloomberg School of Public Health in 2007. Specific causes of erectile dysfunction include stress, high blood pressure, diabetes and injury.

Stress and Anxiety

• Stress and anxiety can prevent a man from achieving an erection by blocking the body's parasympathetic input to the penis, according to WebMD.com. The parasympathetic nervous system is responsible for mediating the body's calm and vegetative functions, such as breathing and heart rate during a nap. It is also responsible for modifying blood flow into the spongy tissues of the penis. Stress and anxiety prevent the parasympathetic nervous system from functioning properly, which, in turn, prevents blood from entering the penis.

High Blood Pressure

• High blood pressure causes erection problems by preventing the arteries that carry blood into the penis from dilating properly. As a result there is an insufficient supply of blood necessary to achieve and maintain an erection. According to the Journal of Urology, 68 percent of men with high blood pressure have some degree of erectile dysfunction. Additionally, some medications for high blood pressure can also contribute to erectile dysfunction, reports MayoClinic.com. Diuretics, or water pills, weaken the force of blood flow to the penis, resulting in weak or no erections. Beta-blockers dampen the body's nerve impulse responses that result in erection.

Diabetes

• Diabetes hampers the body's ability to regulate blood-sugar levels and can ultimately damage blood vessels and nerves that control an erection. Men with diabetes tend to develop erectile dysfunction between 10 and 15 years earlier then men without diabetes, according to MayoClinic.com. Additionally, it is estimated that between 35 to 75 percent of men with diabetes experience some degree of erectile dysfunction during their lifetime.

Injury and Surgery

• Injuries that result in nerve damage (particularly to the spinal cord) can interfere with the body's ability to send signals that start an erection. Surgeries affecting nerves can also cause erectile dysfunction -- especially surgeries used to treat prostate and bladder cancer, according to the National Kidney and Urologic Diseases Information Clearinghouse. Erectile dysfunction can also occur if the smooth muscles of the penis or the corpus cavernosum, which holds a majority of the blood during an erection, are injured.