No idea why you're getting downvoted - they have no control group and as you say there's 'depression' in their symptoms they count for. I'm pretty sure 'depression' (which I'm sure they don't count as clinically depressed, but 'im feeling more depressed') went up significantly in the whole population last year.
Also PLoS one is basically not peer reviewed - they accept every paper after a short review.
Also PLoS one is basically not peer reviewed - they accept every paper after a short review.