I used to have OCD (Obsessive-Compulsive) for a long time, and I pulled out some of my hair. Now it's a few years since I broke the habit, and I find myself substituting ice chewing for other such habits like the hair pulling.
Maybe it's just a substitute for other compulsive behaviors.
I do run borderline anemic, however my ice chewing became a good way for me to get my 8+ cups of water each day! After a stomach surgery I had an awful time getting anything down and was all too often dehydrated, once I discovered I could toelrate the ice I just went with it! And we have this amazing ice at work that is soft and slushy when it comes out of the dispenser ...I easily eat 6-8 cups of it during an 8 hour shift. Of course I get teased by my coworkers, but I do not face the medical problems I used to!
@Timus--The lack of iron brings upon the craving for ice, not the other way around. Many people find that after raising their hemoglobin levels through iron suplements, the craving for ice disappears. Many women become low on iron during pregnancy and begin chewing ice as a symptom of anemia. Once their iron levels are restored after giving birth, the craving subsides. So please do not spread the falsehood that eating ice causes low iron. People who eat ice also eat food. We just prefer the water we consume in frozen form.