Our addiction to reading texts and Facebook posts on our phones is putting about as much stress on our spines as carrying around a big sack of potatoes on our heads each day, a new study suggests.

Dr. Kenneth Hansraj, chief of spine surgery at New York Spine Surgery and Rehabilitation Medicine, says all those hours we spend hunched over our phones is ruining our posture and taking a toll on our necks.

In a new paper he published in Surgical Technology International, Hansraj writes that the average adult head weighs between 4.5 to 5.5 kg (10 to 12 pounds) when standing upright. But the head becomes heavier the more we bend our necks because of gravity.

He calculated that as the head tilts forward 15 degrees, the gravitational force on the neck rises to 12 kg (27 pounds). It rises to 18 kg (40 pounds) at 30 degrees, and 22 kg (49 pounds) at 45 degrees.

At 60 degrees, the force on our neck rises to 27 kg (60 pounds) – about the equivalent of carrying an eight-year-old on your head.

Growing time spent on phones

Surveys show that many adults spend two to four hours a day using their phones for reading and texting. That's about 700 to 1,400 hours a year bent over. A high school student may spend even more time on their phone -- perhaps 5,000 hours a year.

Hansraj writes that all that time spent with our necks bent at an unnatural angle will cause incrementally increased stress on the neck.

This could lead to early wear and tear of the spine and perhaps surgeries down the road.

The solution, he says, is to try to straighten up while texting.

"While it is nearly impossible to avoid the technologies that cause these issues," Hansraj writes, "individuals should make an effort to look at their phones with a neutral spine and to avoid spending hours each day hunched over."