Moving schools itself probably doesn't cause depression, but maybe if you move involuntarily, like if you're moving house and lose contact with the friends you maybe had at your old school.
If you move school because of bullying etc., moving school should hopefully have a positive effect, in that case it's not moving school that causes depression but the reason why you moved school [bullying etc.] that maybe caused depression.
A poll can't decide what's true and what's false, only what most people think is true and false.