Most men will find that occasionally they cannot get a proper erection, or maintain one. This can be due to tiredness, drinking too much alcohol or being stressed or distracted.

Some men experience this problem on a persistent or recurring basis and find that their penis can never become properly erect. This is termed erectile dysfunction, or impotence.

In the majority of cases, this is due to physical causes, although there can be psychological reasons. While erectile dysfunction can occur at any age, it is far more common in older men. Five in ten men over the age of forty suffer from erectile dysfunction and seven in ten men over the age of seventy.

Understanding the mechanics of an erection

Before looking at the various causes of erectile dysfunction, it is helpful to examine exactly how an erection works. It begins in the brain, which is a reason why some erectile dysfunction can be attributed to psychological problems.

The brain sends messages of arousal to the nerves in the penis, which release chemicals called neurotransmitters. These neurotransmitters are also released during physical stimulation of the penis.

This release stimulates the production of another chemical in the penis, cyclic guanosine monophosphate (cGMP), which has the function of widening the arteries in the penis. As extra blood flows through the widened arteries into the penis, it swells.

As it does so, the inner part of the penis presses on the veins near the surface and prevents them draining the blood out of the organ. When the sexual act is complete, the neurotransmitters stop producing cGMP and the blood flow returns to normal, allowing the penis to gradually deflate as the blood drains away.

Reduced blood flow and vascular disease

As can be seen, the unrestricted flow of blood into the penile tissue is a vital necessity for an erection. The vast majority of erectile dysfunction cases, about 75%, are due to narrowing of the arteries in the penis.

This is caused by atheroma; the build-up of plaques of fatty material that form on the lining of the arteries. Atheroma attacks other arteries in the body such as those leading to the heart, the brain and the legs, but those in the penis are usually the first to show symptoms.Erectile dysfunction has been found to be a warning sign that cardiovascular disease is likely to occur. The risk of heart attack is doubled in those with erectile dysfunction and there is also an increased chance of having a stroke.

For this reason, erectile dysfunction should never be ignored, as tests can reveal if narrowing of the arteries is the cause. There are several risk factors that increase the chances of developing narrowing of the arteries in the penis, apart from inevitable ageing.

These include smoking, alcohol and drug abuse and lack of exercise. High blood pressure, high cholesterol levels and diabetes will also impact on the health of the blood vessels, and lifestyle changes can be effective in treating erectile dysfunction caused by narrowing of the arteries.Other Physical Causes of Erectile DysfunctionA low sex drive, reducing the signals sent from the brain and the release of neurotransmitters in the penis, can result from low levels of hormones such as testosterone and prolactin. Hormone production can also be effected by head injury, which can interrupt the functioning of the pituitary gland, located in the brain.

Nerve damage is another physical cause of erectile dysfunction, and can be caused by injuries to the spine or pelvis, surgery, radiotherapy and cycling for long distances.Diseases such as Parkinson’s disease, multiple sclerosis and stroke can have an effect on the nerves of the penis, and certain medicines, including anti-depressants, beta-blockers and diuretics, have side-effects which can trigger erectile dysfunction. A rare, but serious, cause of erectile dysfunction is a venous leak, in which blood flows from the penis at an excessive rate.

Psychological Causes of Erectile Dysfunction

The nerve signals and neurotransmitters that trigger an erection can be affected by various mental health problems. These include depression, anxiety and stress.

A sign that erectile dysfunction has a psychological cause rather than a physical one is if an erection can be obtained in some, relaxed, situations, such as on waking at night, in the morning or when masturbating. Erectile dysfunction due to mental reasons is more likely to appear suddenly, rather than developing gradually over time as it usually does with erectile dysfunction caused by physical problems such as narrowing of the arteries.

Anyone developing erectile dysfunction should see a GP, who will be able to identify the underlying cause by running physical tests and examinations. There are many treatment options, all with a good chance of success, including medication, counselling, lifestyle changes and surgery.