Did they verify non drinkers are non drinkers? My Doctor friend tells me that she is amazed at how many people when asked if they drink, emphatically say "Never".
Cognitive dissonance is widespread. An old roommate once informed me she had given up drinking, because she switched from vodka crans to wine. It's similar to vegetarians who sometimes eat chicken and people who "don't watch TV" because all the shows they watch are on Hulu.
I'd suspect it's less to do with cognitive dissonance, and more intentional lying to meet social norms or out of fear of future problems.
Anything controversial, highly personal, or with stigmas attached will get biased results from self-reporting. Alcohol, drugs, sexual history, religious views, political views, racial prejudices, etc will almost always be biased towards what the person thinks is the right answer.
I personally don't like the taste, nor the side effects - I wish alcohol was the social grease it's touted as, but for me it's only bad side effects.
Nobody in my family drinks (as in, you won't find a single alcoholic beverage at a Christmas party or weekend barbecue for example), and my current girlfriend was a very casual drinker and has quit since she started dating me.
Many of the surveys I've seen in doctors offices & similar don't distinguish well between "almost never" and "never". I know a fair number of people in my family are in the "almost never" category. They might have a glass of wine at Christmas or Thanksgiving dinner, but that's about it. I don't know what they tell their doctors, but given the usual checkboxes for frequency of alcohol consumption, "never" is probably what I'd select.
