Well, alcohol can have an effect on a persons mood making them more depressed and what not, but that doesn't mean everyone is like that. Some people can drink even get drunk occasionally without feeling negative mood effects, even some people who are depressed. The reason that they warn people not to drink while taking Zoloft is because there are plenty of people, especially the depressed, who find it effects their mood negatively. Also, I find anecdotal evidence, that antidepressants + alcohol = drunk faster and further impaired judgement especially stimulating antidepressants like Zoloft and Prozac that make you feel more like a wide awake drunk (like mixing energy drinks with alcohol) rather than realizing just how drunk you are. Also, antidepressants can, for some people, increase risks of suicide and impulsive behaviour and decrease quality of sleep, as can alcohol. Another reason it is discouraged to drink while taking antidepressants is that some people use alcohol for anxiety symptoms, 'cause alcohol will temporarily calm you down, but if your antidepressant is causing you to be more anxious or to have more/too much energy, alcohol is not going to fix it (you need to see your doctor for that) and you're increasing your likelihood of becoming more than just a social drinker.