In the study there were three groups A) No phone use B) Normal phone use C) Phone use with night shift They found no group differences. edit: They did find

In the study there were three groups A) No phone use B) Normal phone use C) Phone use with night shift They found no group differences. edit: They did find a differences for some subgroups (i.e. sleeping more than the median). I have to admit I only had a quick look at the paper.