Can external pressure damage iPhone 4 screen?

So when I go to school I always put my iPhone 4 in a small pocket in my backpack. However, I stuff my books and binders in there as well, and sometimes I'm unaware if one of my textbooks is accidently crushing my phone.
I've noticed recently that my phone has these static lines at random times. Could this be one of the reasons why?

The screens of iphones are too delicate to handle. It depends on the time your books have spent over the screen of your iphone resting. The bottom-line is, stuffs and binders can damage the screen of your iphone. Make sure the damage is not so harsh and adopt measures to protect the screen. Try to find out a new place for your iphone.