Why do people experience intense yawning during opiate withdrawal? just curious as i never understood why!

Brainstem rebound: Opiates affect to a large extent the brainstem region where autonomic functions reside (breathing, blood pressure, GI motility, etc). Opiate withdrawal can be thought of as the OVERCORRECTION or REBOUND of these functions causing a paradoxical OVERDRIVE if you will stimulated by the lack of the drug's presence. Yawning is one of the early phase symptoms (8-12 hrs). Usually goes away within 48 hrs

Cool the brain: University of Vienna recently released a paper on this. It used to be thought it had something to do with increasing oxygen but studies could not confirm this. Research in Albany NY showed that contageous yawning could be suppressed by applying a cold ice pack to the back of the head. A warm pack did the opposite. Opiate withdrawal leads to increased brain activity and increased need for cooling.