Erectile dysfunction, or impotence, is the inability to achieve or sustain an erection that is suitable for sexual intercourse. It can be caused by medications, chronic illnesses, poor blood flow, drinking too much alcohol, fatigue, smoking, injuries, obesity or clogged blood vessels. Different factors can worsen erectile dysfunction, including depression, anxiety and stress. The occasional inability to have an erection usually isn’t reason for major concern. However, if erectile dysfunction is an ongoing problem, it is important to see a doctor because it could be a sign of a health condition, such as heart disease or diabetes.