Is it bad to have an alcoholic drink every night, even if it's just one?

Depends: Many factors including personal and family history of drug and alcohol abuse/dependence, ones medical history, the size of the drink and the reason for use would color my opinion. In general however recent reports have indicated that moderate drinking (defined as one drink per day for women) may lessen the risk for cardiovascular disease- r this amount of use also increases the risk of accidents.

Not usually: But it depends on the size of that one drink and how much alcohol it contains. A "beverage alcohol equivalent" is equal to one 12 ounce beer, 4 ounces of wine or one ounce of whiskey or hard liquor. For most people, having one drink per night isn't harmful. Some studies suggest that there is actually a benefit to one drink per night, especially red wine due to the antioxidants. Check with your dr.