It has varied causes, including adjoining tables with loud people who never STFU*, PITA parties who stick around way too long and take forever to leave once they start the process of departure**, and children who race around the restaurant while their oblivious parents are absorbed in their cellphones.
Signs and symptoms include involuntary glaring, elevated blood pressure and a desire to eat at home.
*the nonstop talker invariably has the most annoying/ultraloud voice.
**and then congregate in the parking lot to continue the Endless Goodbye, blocking traffic.
Those children do more than just race around the restaurant. They crawl under tables, kick seatbacks in booths, yell and scream, and climb over interesting architectural features of the building.
My son had ADD when he was grade-school age. It took a lot of hard work, perseverence, and patience on behalf of my husband and myself to get him to be a well-behaved diner when we would go out as a family. When the heathen children of other families would tear up the place while their oblivious parents did nothing, my son was actually one to make remarks about the disruptions.