[fbdab103]

Associated typically means, "we saw these two things together". Maybe there is an underlying connection, but it at least looked funny (and/or enough to get a paper out the door).

Which is honestly about the best you can get from human behavior. Unlike rats, you cannot lock up humans for their lifetime, force-feeding them a diet of gruel for trial A meanwhile trial B gets a diet of corn-syrup and beer.

Better studies will try to subtract out meaningful differences (eg smokers vs non-smokers), but there is only so much that can be done when humans lie, cheat, steal, and misremember their behavior on questionnaires they fill out years after the fact.