According to a recent study excessive amount of leaning your head forward and down, while looking at a phone or other mobile device may result in what some people call text neck.

Text neck is defined as overuse syndrome involving the head, neck and shoulders, usually resulting from excessive strain on the spine from looking in a downward position at hand held devices such as cell phones, mp3 players, e-readers and computer tablets.
"When you hold your body in an abnormal position, it can increase stress on the muscles, cause fatigue, muscle spasms and even stress headaches," Cornett said.
"With every degree of motion to the front or side that you move your head, the stress on your neck is magnified beyond just the weight of the head," he said.
He added that what we assume, but do not necessarily know, is whether or not this is causing long term increased stress on the other structures in your neck, like discs and joints.
Source-ANI