ED is divided into organic (having to do with a bodily organ or organ system) and psychogenic (mental) impotence, but most men with organic causes have a mental or psychological component as well.

Physical causes

An erection works by allowing blood into the spongy tissues of the penis but stopping it from flowing back out again.. Anything affecting the arteries, veins or nerves that supply the penis will influence the ability to have an erection. These can include:

Medicines such as anti-depressants and drugs for high-blood pressure (such as ACE inhibitors and beta-blockers);

Alcohol, smoking, and taking illegal drugs;

Conditions that affect the nerves or blood supply, such as multiple sclerosis or a stroke;

Diabetes, which can sometimes cause a problem with the nervous system;

Blood vessel conditions such as blocked arteries (for example, caused by high cholesterol levels);

Hormonal conditions, such as not having enough testosterone in your body, or having too much of another hormone called prolactin;

Conditions affecting the erectile tissue of the penis, such as prostate cancer;

Serious long-term conditions such as kidney or liver failure.

As you get older, you’re more likely to have another condition that causes erection problems, such as heart disease or diabetes. But that doesn’t mean you shouldn’t seek treatment for your erection problems, as well as the underlying condition.

Psychological causes

Some of the most common psychological causes of erectile dysfunction include:

Stress or anxiety,

Depression, and

Relationship or sexual identity issues.

Sometimes an occasional erection problem caused by a minor everyday problem such as a few too many drinks, or a particularly hard day at work, can begin a cycle of worrying. This can turn into a psychological cause of further erectile difficulties.

Treatment

Treatment depends on the cause. Testosterone supplements may be used for cases with hormonal deficiency. However, usually the cause is lack of adequate penile blood supply as a result of age-dependent damage of inner walls of blood vessels. Previously, medical substances (e.g. apomorphine) were directly injected into the erectile tissue of penile shaft to treat impotence. In some cases refractory to the medical treatment, a penile implant (penile prosthesis) could be advised. After the discovery of orally active agents that increase the efficacy of NO, which dilates the blood vessels of corpora cavernosa, more conservative methods started to be used.

The prescription PDE5 inhibitors sildenafil (Viagra®), vardenafil (Levitra®) and tadalafil (Cialis®) are prescription drugs which are taken orally. They work by blocking the action of PDE5, which causes cGMP to degrade. cGMP causes the smooth muscle of the arteries in the penis to relax, allowing the corpus cavernosum to fill with blood.