In the novel To Kill a Mockingbird, explain Mrs. Dubose's addiction to morphine and why she was so grouchy while being addicted to it?

In Chapter 11, Jem loses his temper after Mrs. Dubose makes several derogatory comments about his father. Jem's punishment is to read to Mrs. Dubose for two hours every day, except for Sunday. Later on in the chapter, Jem notices that his reading hours become longer, and Mrs. Dubose stays awake for longer periods of time each day correcting his reading. When Mrs. Dubose dies, Atticus explains to Jem that Mrs. Dubose suffered from a chronic illness and took morphine to ease the pain. She asked Atticus if he could help her, and Jem's reading kept Mrs. Dubose occupied and her mind off the pain in between her morphine doses. Mrs. Dubose's final wish was to die free of her addiction. Each day, Jem would read for a little bit longer, thus increasing the time in between doses of morphine until her addiction was broken. Mrs. Dubose was in extreme discomfort while Jem was reading to her, which probably resulted in her grouchy attitude. Also, addicts who suffer from withdrawal symptoms are extremely irritable, which explains why she would continually harass Jem while he was reading.