Pinkie pie does not have schizophrenia. To have schizophrenia someone needs to have deteriorated in everyday functioning and must show AT LEAST 2 of the following symptoms, that are not attributable to other disorders: - Delusions - Hallucinations - Disorganised speech - Grossly disorganised behaviour - Weak or absent signs of emotion, speech, and socialisation Pinkie may occasionally exhibit disorganised speech and behaviour, but nowhere near what psychologists would expect from someone with schizophrenia. Most likely psychologists would diagnose Pinkie Pie with ADHD. Rainbow Dash has more than enough of the symptoms of Narcissistic personality disorder, and easily fits those criteria. Rarity is a little exaggerated, and a little detail-oriented, but I wouldn't immediately class her as having a personality disorder. Twilight Sparkle, in my personal opinion, just doesn't know how to deal with stress. I wouldn't even class her behaviour under OCD. OCD presents itself through obsessive ritualistic behaviour that is. Twilight may be incredibly organised, but she isn't obsessively washing her hooves, or obsessively following a specific behaviour every day (think of picking up a book, putting it down, piking it up again, and then placing it back down - an illogical action that to a person with OCD NEEDS to be done or else something bad will happen). She has some obsessive tendencies, but that doesn't immediately translate to OCD. Besides, If anybody has noticed; since Twilight became an alicorn and gained her princess status, her obsessive tendencies have gotten much less. Most likely, she was having study related panic attacks. In lesson zero she was freaking out because she was going to miss a deadline (I can absolutely relate to the twitching in that scenario), but once Celestia told her she didn't need to send letters every week, she stopped obsessing over it. people with OCD don't just stop obsessing over something because someone says "it's okay" Fluttershy has social anxiety, but she copes really well with it! Applejack has no disorders. She may be so hard-working that it nearly breaks her back, but mentally, she's healthy (besides the occasional panic attack, which everyone experiences at some point)