the worst part is that a study like is claimed here would be maybe even possible but is in no way behind that click bait title. to actually prove this a large r

the worst part is that a study like is claimed here would be maybe even possible but is in no way behind that click bait title. to actually prove this a large randomised test group (thousands not hundreds) with no current diagnosable form of depression would have to be followed over a time long enough so a significant part of them are expected to develop depression in the course of the study. 50/50 random individuals are forced to get up earlier or later, just changing sleep pattern of the early risers would destroy comparability. The hard part is properly controlling for compliance, drop outs, spouses and jobs etc. a subject with onset of depression is more likely to drop out when forced to get up uncomfortably early and a subject with a fulfilling demanding job is less likely to be able to continue sleeping long for a long term study etc. The relationship of sleep and depression has been known for decades but to properly study the real causality here is harder than most think.