Slow internet speeds can actually stress you out
The study found that a person's heart rate can increase by around 38% as a result of mobile content delays. Meanwhile, the level of stress caused by mobile delays was comparable to that caused by watching a horror movie. It may be wise to avoid watching a horror movie on mobile...
As for that buffering wheel on YouTube, that can cause a fair degree of stress too. The study found that a two second delay in a YouTube video starting increases stress by three percentage points, while just a single pause as a video is playing can cause stress levels to rise by an additional fifteen percentage points.