Why was Mary put on pills when she was a child and why did she quit taking them?

Ray kept coming into Mary's room and trying to get into Mary's bed. Usually, she kicked and cried like a wild animal. Then she had bitten down on his arm and drawn blood. Ray told Dawn that he was just checking on Mary and they needed to get her help. They took her to a doctor who was a friend of Ray's. The doctor used words like "hyperactivity, neurobehavioral, comorbid, and oppositional defiant" (100). Then he prescribed some pills for Mary. The pills made Mary almost too slow and sleepy to watch out for Ray, so she refused to take them.