Disorder(s): schizoid personality disorder, may possibly have an autism spectrum disorder (would most likely be Asperger’s Syndrome)
Positive traits: Extremely high intelligence, extremely observant and perceptive to details, possesses creative imagination, keen ability to focus and concentrate outside of exterior distractions, keen ability to understand and predict human behavior, extremely developed ability to make connections using seemingly unrelated data
Negative traits: Inability to empathize with others, disregard for authority, high level of stubbornness, narcissistic, inability to properly deal with emotions, inability to properly deal with boredom, ignorance of common sense and simple knowledge, tendency to overthink and/or overanalyze, inability to conform to social norms
Notes: Sherlock possesses emotions, however, he makes the purposeful decision to suppress them because he believes that emotions obstruct the ability to reason logically, which is a skill that he needs to solve cases. He solves cases to relieve boredom, which is a severe problem for someone of his intelligence to face, and one that he has been battling since most likely early childhood. Sherlock may have also developed this capacity to ignore emotions from a troubled childhood, possibly verbal abuse or constant bullying. This abuse may have caused him to protect himself with a thick, seemingly impenetrable wall, as evidence by the statement “alone is what I have, alone protects me”. This may be indicative of constant betrayal.
Sherlock is not a sociopath. I believe this was a misdiagnosis on his part. A sociopath is any individual with anti-social personality disorder, and although Sherlock displays some traits of the disorder, he does not display enough to be diagnosed as one. He does not lie or deceive for personal pleasure, he is not prone to aggressiveness, and he is capable of feeling guilt and remorse, which has occurred several times in the series, particularly in regard to Molly Hooper. He is also capable of forming lasting, meaningful relationships (John Watson, Mrs. Hudson), which is something that a sociopath cannot do.
Sherlock’s relationship with John Watson is also interesting. Sherlock is an obvious show-off; he greatly enjoys it when people praise his intellect, and he takes pleasure in proving that he is more clever than those around him, and feels threatened when his position of intellectual superiority is in danger of being toppled. He dislikes it when people attempt to change him or tell him what to do; he appears to have problems with authority, particularly with his brother Mycroft Holmes. John is one of the few people that have complimented Sherlock’s abilities, as well as allowing Sherlock to be himself instead of trying to alter his behavior.
The reason why Sherlock often arrogantly shows off his intellectual prowess is because he is actually insecure; he believes his intelligence is his only good quality, and he puts a lot of emphasis on that particular trait. Sherlock himself may not be aware of his insecurities; in fact, one of Sherlock’s weakest points is that he is accurately aware of everything but himself. His perception of himself seems to be rather skewed; he does not believe in himself, rather, he believes in a caricature of himself: a heartless, cold, logical, deduction machine, instead of a human being.
Sherlock appears to be very detached. He considers himself alone in more ways than one; he believes that he is not only separate from the rest of society, but also above. (Remember A Scandal in Belgravia? Molly says, “Well, we all do silly things,” and Sherlock replies by saying, “Yes, they do, don’t they?” He used the pronoun “they” instead of “we” almost automatically, as though he considers himself apart from the “we” that Molly is talking about, i.e: humans in general). He knows that he is not normal, and he denounces those who are. Sherlock may have a slight complex involving the acknowledgment that he is only human; as Irene Adler said, he believes in higher power: himself. He constantly pushes boundaries: testing the limits of his body by refusing to eat or sleep during cases, testing the limits of his emotions by suppressing them, testing the limits of his humanity by behaving almost inhumanely, testing the limits of those who care about him by pretending to not care for them (when he so obviously does).
There is also the interesting relationship between Sherlock Holmes and James Moriarty. Sherlock obviously wants to defeat Moriarty; but it’s the reason that is revealing. Sherlock seems to be divided by the urge to defeat Moriarty because he is a criminal and it would simply be the right thing to do (in fact, it would be the kind of thing a hero would do), or to defeat Moriarty simply to win a challenge made against his intelligence; basically, as a battle of wits. And Moriarty knows this and uses it to his advantage (The Great Game; Sherlock asks what were to happen if he were to shoot Moriarty right now; Moriarty claims he would be surprised. One may suppose that the reason why it would be surprising would be because Sherlock is not stupid enough to risk his and John’s life by doing that, but I think the real reason is that Moriarty knows that Sherlock wouldn’t kill him because then he would be eliminating the best distraction, the best challenge, he has ever had. It was an implied accusation that Sherlock needs Moriarty so much that he would selfishly spare him in order to enjoy the thrill of solving his puzzles. This was expounded up in The Reichenbach Fall, when Sherlock says “I am you.” They are one and the same; neither can live without the other. If one dies, the other must die as well. Moriarty realized this, and thus he killed himself to ensure Sherlock’s death and defeat.) And from a psychological point of view, Moriarty and Sherlock have a lot of very striking similarities. They are both unable to deal with boredom; while Moriarty creates chaos to distract himself, Sherlock solves chaos. This may be due to the fact that Sherlock appears to have a conscience which Moriarty lacks. Sherlock may seem cold and even cruel, but he is certainly not cruel enough to murder or hurt innocent people, even though he certainly could get away with it.
Many of Sherlock’s most notable traits (his violin-playing, his cocaine addiction, his smoking addiction, his science experiments) culminate from his boredom; boredom defines Sherlock. It accentuates Sherlock. Without the boredom that is caused by having such a quick and advanced mind, Sherlock would not be the famous detective. Intelligence is everything to Sherlock Holmes; it is the trait that he is the proudest of and the most protective of. He would risk his life to prove that he is clever, and he would do anything to outsmart someone who is a match for his intelligence. He spends so much time and energy showing off this trait and brushing up on it, that he neglects other things that are important such as emotions, happiness, and health, because they are not as important to him as intelligence.
On a different topic, I find Sherlock Holmes’ manner and behavior interesting. He speaks very rapidly and very precisely, failing to notice or care whether others can understand him (often using vocabulary that is overtly advanced and is often peculiar to the situation), and his eye contact is odd; he either retains eye contact too long and abruptly looks away, or he refuses to look at the person he is speaking to. These are traits that are common in children or adults with Asperger’s syndrome.