There are both physical and psychological causes of ED and most men will experience a combination of these causes, with one type affecting the other and vice versa.

Men whose ED is due to a physical cause often experience a gradual onset of erectile problems. These physical causes can include:

• Cardiovascular disease (CVD)
• Diabetes
• Raised blood pressure (hypertension)
• Hormone problems
• Drinking alcohol
• Smoking
• Lack of exercise
• Using illicit drugs 
• Some prescription drugs, e.g. some diuretics, antidepressants and hormone modifying drugs.

ED can be an early warning sign of future cardiovascular problems, appearing up to five years before a cardiovascular event, such as a stroke or heart attack.

Future heart problems may be prevented if treatment for ED is undertaken soon after symptoms start, particularly if lifestyle changes are undertaken.