It might well be that meditators react to situations less stressfully, so that it's actually stress that's the negative agent rather than meditation the positiv

It might well be that meditators react to situations less stressfully, so that it's actually stress that's the negative agent rather than meditation the positive one; and so any stress-reducing activities will have similar benefits. To show causation, it seems (I'm not a statistician) would require eliminating a lot of factors: diet, lifestyle, etc.