I always wonder what are the causes and what are the effects in studies like this one and the ones that say drinking is healthy. Is it possible that those who l

I always wonder what are the causes and what are the effects in studies like this one and the ones that say drinking is healthy. Is it possible that those who lead healthier lives are therefore mentally able to resist from drinking, and not the other way around as this study shows? The same applies to the studies that say those who drink a little are healthier than those who don't. As JofArnold said in another comment here, those who don't drink at all may only be less healthy because they are the people who are likely to stress over things. I'm sure the scientists conducting these studies try to eliminate these inconsistencies to as much as their ability by establishing the cause-effect relationship, but it seems impossible to do this exactly right and thus we should consider the associated problems in studies like these.