Traumatic Causes.

Trauma or injury to the penis, spinal cord, prostate, bladder, and pelvis can lead to erectile dysfunction by harming nerves, smooth muscles, arteries, and fibrous tissues of the corpora cavernosa. Bicycle riding for long periods has also been implicated as a cause of erectile dysfunction.

Some types of prostate or bladder surgery. Surgery of the colon, prostate, bladder, or rectum may damage the nerves and blood vessels involved in erection.

Medications.

A great variety of prescription medication are known to cause or contribute to erectile dysfunction:

blood pressure medication (especially beta-blockers)
heart medication
antihistamines
antidepressants
tranquilizers
antipsychotics
anticonvulsants
appetite suppressants
anti-ulcer medications
sleeping pills

Psychological conditions.

Experts believe that psychological factors cause 10 to 20 % of erectile dysfunction cases. Anxiety and guilt are the most common psychological causes of erectile dysfunction. Depression, worry, stress, low self-esteem, and fear of sexual failure all contribute to loss of libido and erectile dysfunction.

Substance abuse.

Alcoholism. Drinking too much alcohol interferes with the production of the male hormone testosterone, which can reduce libido.

Smoking is considered an important risk factor for erectile dysfunction because it is associated with poor blood circulation and its impact on cavernosal function.

By Yury Bayarski, Source: on-line-tribune-health.blogspot.com