King never really details Annie's medical condition with full disclosure.  We know something is wrong, terribly wrong with Annie.  The lack of full details helps to enhance the theme that fame is often a cage, whereby full understanding of its implications is unknown.  Paul knows that fame has consequences, yet he never had any idea it would be to this extent.  Annie displays signs of bipolar disorder with her intense mood swings.  These are characterized by periods of intense energy and stifling depression.  The mood swings are characterized by her language.  Terms like cocka-doodie" and "dirty-birdy" help to highlight her intense energy, even in recreating language.  Yet, her stoicism at moments, when she is as still as an "African statue" also reflects the downside to her mental state.  At the same time, King does display the notion of the psychotic, with Annie's "disconnect" and intense moments of extreme apathy combined with excessive care.  In this roller coaster of intense emotion, there is much in way of bipolarism and the tenets of bipolar behavior.  It might be real important to avoid giving Annie labels such as "psycho" without a full workup because such labels tend to demonize the basis of the true terror of the character and the full implications of the novel.