The canadian erectile difficulties resource centre 

What causes ED?

There are two answers to this question. The first deals specifically with the actual erection mechanism in the penis. The other looks at the many factors that may affect that mechanism.

The penis' perspective

When a man is sexually aroused, the arteries in the penis relax and widen, allowing more blood to flow in. As those arteries expand and harden, the veins that normally carry blood away from the penis become compressed, restricting the blood flow out. With more blood flowing in and less flowing out, the penis gets bigger, resulting in an erection.

While it may sound simple, an erection is the result of a delicate but perfectly balanced process that involves the brain, blood vessels, nerves and hormones. If any one of those elements isn't working properly, it can cause a problem with the events that enable the penis to fill with blood. The result is called ED.

The bigger picture

Here are some common causes of ED that may affect your ability to have an erection:

• Medical conditions that may block the blood flow into the penis (e.g., high blood pressure, high cholesterol, diabetes, and hardening of the arteries).
• Nerve damage that interrupts the connection between the nervous system and the penis (e.g., spinal cord injury, multiple sclerosis, stroke, prostate surgery or other surgery to the pelvic area).
• Psychological conditions that can lower the brain's response to sexual stimuli and interfere with the ability to have an erection (e.g., anxiety, depression or stress).
• Kidney or liver disease or hormonal disorders that can throw off the delicate balance of the body's systems, making it impossible for the normal erection process to occur.
• Some prescription and over-the-counter medications (e.g., medications for high blood pressure, antidepressants, some drugs used to treat cancer and epilepsy).
• Cigarette smoking, obesity, excessive alcohol consumption and recreational drug use can interfere with normal bodily functions, and therefore the ability to have an erection.