It is amazing what kind of physical symptoms we can show from stress. Stress affects us both on the inside and can show up on the outside in the form of facial tics in adults and kids.
I work at a daycare and had a child that had frequent facial tics. I realized this was something she had no control over, but wondered what caused the symptoms. When I found out there was a lot of stress going on in her family, it made sense that stress could have been playing a big part in her tics.