The most obvious disorder depicted by the movie, it must be pure delusional, hallucinatory, paranoic insanity that Horton has not yet become the mascot of schizophrenics of the world.
Not only does Horton hear voices from dust particles, perceive the world as an anime, bursts out into random song, is an outcast, and suffers bouts of clinical depression, but eventually, through sheer force of nature and perseverance, he succeeds! And he gets the world to accept and believe in him -- the ultimate delusion them of all.
Not only does the good Dr. Seuss illustrate the effects of bulimia, but he takes an extra step of greatness that most doctors never reach by actually judging the disorder. By assigning this evil to communist foreign villain, Vlad Vladikoff, Dr. Seuss shows the world what he thinks of this shameful wickedness.
Also notice that the name "Vladikoff," itself, is a near-homophone of "bladder cough," when said in an evil Russian accent -- another indication that bulimia is just the equivalent of making your mouth a penis/vagina and then coughing with it. But only if you're socialist.
Obsessive Compulsive Disorder
At one point in the film, Horton meticulously picks, groups, and categorizes 9,005 clovers in an effort to re-claim his insanity -- which, of course, he finally achieves when when he starts hearing voices again.
Dr. Seuss teaches us that, not only should you work for you insanity, but you should be happy when you find it, because it's what makes you unique, and what you're ultimately classified as in history.
Furthermore, taking place in a field of clovers, the aforementioned scene is, of course, also secondarily an allusion to Cloverfield, re-assuring us that motion sickness and death are inevitable parts of humanity's monstrous nature.
While not in the movie, per se, notice how the title is phrased as a question, and yet is punctuated by an exclamation mark so that Horton Hears a Who? turns into a shout.
This choice effectively equates a question mark with an exclamation and, by extension, uncertainty with screaming. This is yet another brilliant, but subtle masterstroke that conveys to the throngs retards out there (many of whom are reading this) that, when you don't know something, just SHOUT IT OUT LOUD and people will think you're making a bold statement.
Other disorders covered by Dr. Seuss's treatise include:
- Trypanophobia: The Mayor's fear of sharp objects is rational, just like yours!
- Introversion: When depressed, misunderstood, ignored, and surrounded by 96 women you can't have relations with, turn goth and make your own kind of music.
- Multiple Personality Disorder: If you're lucky, you'll have Horton's talent of temporarily disfiguring your body to match your inner essence. If not, go here.
- Fascism: Like bulimia, this is is an evil type of insanity, as personified by Sour Kangaroo.
- Antisocial Personality Disorder: Finally, if you have faces like these, you're probably just dumb and evil.
Horton Hears a Who!: 6/10