The crossword solution for the term 'CAUSES YAWNS' is 'BORES'. Boredom is a common cause of yawning. Yawning is an involuntary reflex that can be triggered by fatigue, stress, or boredom. When someone is bored, they may yawn in order to signal their lack of interest in the activity or conversation at hand. Yawning can also be contagious, so when one person yawns, it can cause others to yawn as well.