Many different conditions can lead to ED. Most of the causes of ED are health problems requiring treatment to help prevent more serious complications than ED:

• High blood pressure and high cholesterol can injure the arteries that supply blood to the penis.
• Diabetes injures blood vessels and the nerves that control erections.
• Alcohol and drug abuse can cause ED by damaging blood vessels and deadening the nerves that control erections.
• Some prescription drugs such as some antidepressants or some high blood pressure medicines can cause ED. Your doctor may be able to change your drug treatment. Never stop taking a prescribed drug without talking to your doctor.
• Unhealthy habits like smoking, overeating, and avoiding exercise can also contribute to ED.
• Anything that’s bad for your heart is also bad for your sexual health.
• An injury to the spinal cord can cause ED by interfering with nerve signals.
• Treatments for prostate cancer, including radiation and prostate removal, can damage the nerves that control erections.
• Diseases that affect the nerves, like multiple sclerosis, can also lead to erection problems.
• A small number of ED cases result from a reduced level of the male hormone testosterone.
• Doctors used to believe that most cases of ED resulted from mental or emotional problems. We now know that most ED has a physical cause. But depression and worry or anxiety can still cause ED. And ED from physical causes can lead to depression and worry, making physical ED worse.
• A person should not assume that ED is part of the normal process of aging. There is quite likely an underlying cause.

Source: National Kidney and Urologic Diseases Information Clearinghouse