Imagine being happy and easy going and all of a sudden somepony kidnaps you and force medications on you that make you stop being who you are because “you have too much fun”.
Wrong. RD has NPD, GAD and mild hypochondria, like a proper celebrity. She talks about herself and her accomplishments so often, she’s an obvious narcissist.
Twilight Sparkle is clearly HFA/Aspie, but with mild OCD tendencies. The dead giveaway for this is her typical pattern of speech. She is most comfortable when monologuing intensely about her interests, but clams up when drawn into reciprocal dialogue. That’s Asperger’s. She also has some rather profound and visible anger issues.
Both Rarity and Applejack are neurotypicals, but workaholics and perfectionists. Applejack is the furthest thing from antisocial imaginable. She is comfortable running a market stall and is adept at sales. Rarity has a mild nonspecific cluster B-ish penchant for overdramatization, but without the debility typical of, for instance, histrionic disorder. She’s mildly eccentric at times (ever-so-slightly schizotypal) but otherwise normal.
Pinkie Pie and Fluttershy are both bipolar/borderline and have fears of abandonment, but express it differently, and Pinkie Pie is admittedly hyperactive.
None of them have problems socializing. Fluttershy socializes easily and often. She doesn’t fear socializing specifically, she has hypersensitivity and fears novelty and unexpected situations in general.
None of them have attention deficit disorder. All of the Mane Six are 100% capable of boring, rote tasks. Rainbow Dash doesn’t shy away from some things because they’re actually boring. That’s just what she uses as an excuse. She does it because she believes it’s beneath her.
In order of normal to eccentric, it’s Applejack (just a bit of overwork), Rarity (ditto), Rainbow Dash (shivering mess), Fluttershy (screaming at animals in a zoo) Twilight Sparkle (“I’ll make a friendship problem!”), and Pinkie Pie is easily the nuttiest.
I agree with Rainbow Dash and Fluttershy but that’s about it. As someone with Asperger’s myself, there have been moments when I’ve related to Twilight, but it really wouldn’t take much to convince me that she’s not, at least in FiM. Sci-Twi in Equestria Girls definitely feels more like an aspie to me. Honestly, I feel like OCD fits better for Twilight (See “Lesson Zero”). Speaking of which, for Rarity, I can see how some people think she has OCD, but I think it’s been pretty well established at this point that she doesn’t (See “Sisterhooves Social”). I don’t know much about ADD, but I think Pinkie Pie could have either Bipolar Disorder and/or depression (See “Party Of One”. As for Applejack, I don’t even know why anyone would assume that (I’m not a big Applejack fan myself). Anti-Social Personality Disorder, along with Narcissistic Personality Disorder, are both primarily characterized by a severe lack of empathy. A trait that Applejack clearly doesn’t possess. I did think that maybe this meant some kind of personality disorder link with asociality (ie. an aversion to social interaction), but even that wouldn’t fit with Applejack at all. Maybe that is supposed to be a joke, like that “Murder is Okay” meme, but if so, that isn’t very clear.
One could argue that Pinkie Pie has ADHD-PH while Rainbow Dash has a much milder form of ADHD-C. In case you’re confused, PH stands for “primarily hyperactive” and C stands for “combined”.
Apparently calling it ADD/ADHD is outdated now. IDK.