In 75% of all the impotence cases the causing reasons are of physiological character. Among them are:
age: about 10% of men after 40 are suffering of erectile dysfunction. At the age of 70 their quantity is about 60%.
vasoconstriction or blood vessel dilatation: high content of cholesterol and high arterial pressure may become first signs of future impotence
diabetes: destroys small vessels including the ones in genitals
adverse reaction of some drugs that affects nerve endings functioning in genitals. Among such drugs are antidepressants and preparations to lower blood pressure.
hormone imbalance: for example low testosterone content
nervous disorder caused by psychological trauma or physical injury, extensive sclerosis
smoking that causes deterioration of circulation of the blood, chronic alcoholism and drug addiction that bring to nervous system disorder
Among psychological causes physicians name continuous anxiety, feeling guilty and depression. If a man has morning erection and masturbates periodically, then the reason of impossibility to have a coitus with a partner has a psychological character.