hello user , i understand your concern . alcohol use has both short term and long term side effects on body - consuming it in large amounts can lead a person to alcohol intoxication which can further be fatal also - in long term side effects it affects almost all systems of body like in gastrointestinal system it can cause gastristis, pancreatitis,alcohol liver disease- liver cirrhosis, peptic ulcer and malignancies like gastric and esophageal carcinoma - it decreases the fertlity also in long run along with hormonal imbalances, can cause neuropathies, memory disturbances , can affect heart inform of myocarditis and cardiomyopathy and practically every organ of body . so ideally your son should quit drinking , but caution is that it is to be done under medical supervision as sudden stopping or reduction of use can produce troublesome withdrawl symptoms like seizures , delirium etc. so you should consult him with any good psychiatrist in your vicinity for deaddiction . Take care