As Shakespeare once said, "alcohol increase the desire but takes away the performance." Not only are alcoholics unable to perform, but their liver function also deteriorates, resulting in excessive levels of the female hormone, estrogen, which has a severe sperm- suppressing effect. These also alter hormonal balance and testicular function and cause impotence & erection problems.
Alcohol is essentially a central nervous system depressant. Chronic alcoholism impairs the sexual functioning due to many causes. Besides it results in hepatic and neuralgic damage. This leads to impotence.

Prolonged drug abuse also causes impotence as that of alcoholism drugs used as ‘aphrodisiac’ or continuous intake of toxin drugs such as marijuana, cocoine etc create dangerous ill effect in the body system and leads to permanent impotency may be these drugs, at the beginning induce some sex stimulation, but prolonged use will cause negative side effects.