Report Abuse. 1  Involuntary Jaw Movement. Source(s): https://shrinke.im/a9mZ5. 2  I know that some people can tend to continue to do the moving of their jaw because its a habit and sometimes habits are hard to break. So it can just reflex from when they use to do the drugs. It is good that you are worried about them, because some people tend to go back to drugs.