While you’re enjoying a delicious meal, the small intestine begins to produce the hormone CCK which aids digestion by slowing down the movement of food, triggering the production of bile and other enzymes, and stimulating the feeling of fullness even before your plate is empty. While CCK is mostly associated with the small intestine and digestion, new research is beginning to study how CCK produced in the brain may have an affect on mental health issues like panic and anxiety disorders.