Is there always a root or a cause?

I've read that some people started picking after being abused or experiencing other traumatic events. I've seen a couple of psychs and counsellors about my picking condition and they have all tried to get to the bottom of what happened to me when I started picking. I've got no idea! I thought I was just another slightly self conscious and stressed teenager with some acne. I squeezed some pimples - a little more than my peers - and before I knew it, my picking and squeezing had developed into a habit. Is there always an event or experience that causes a person to start picking?