
On par with bring an eccentric genius with trouble at conforming to social behavior, the show has hinted at symptoms correlated with schizophrenia, (minor) autism, and Asperger's Syndrome, as evident by his bursts of long-winded commentary, his impressive academic history (three PhDs in Mathematics, Chemistry, and Engineering) in a short amount of time, and adverse reactions when touched by strangers. Gubler tweeted that Reid is also germaphobic. Matthew Gray Gubler has also commented on the differences between Reid and similarly odd character Garcia: "She represents everything he is not, she is very tech oriented and I would like to imagine he is more like 1920s smart, books and reading etc." Reid is a technophobe and does not use either email or the new iPads. Reid also had a hard time feeling empathy, among other emotions, until after the events of season two, stating that he could understand what the victims felt before they died to Morgan in " Fear and Loathing". He tends to miss social cues at times (for example, unknowingly changing the subject of a conversation).

He has an affinity for words - from reading and scrutinizing texts at an astounding 20,000 words per minute (an average American adult reads text at 200–300 words per minute) and his rambling of long explanations and tangents (prompting Morgan and other team members to have to tell him to be quiet).

Reid is noted for his social awkwardness and prodigal brilliance, which draws on his analytical way of thinking and establishes him as the encyclopedic brainiac of the group. Despite that, he has been able to perfectly recite speech he hears, even when it was in a completely different language of which he didn't speak a word (" Corazón"). However, his ability to retain auditory information has been rather inconsistent, as evident when he once noted he could not remember Garcia's name (" Tabula Rasa"). This, however, only definitely applies to information gathered visually (especially things he's read, as implied with the word eidetic). Reid has an eidetic memory, meaning that he can remember an exceedingly large amount of information with extraordinary detail. Reid is also worried about the fact that his mother's illness can be passed on genetically he once told Morgan that "I know what it's like to be afraid of your own mind". Until Season Twelve, she resided in that same mental institution and Reid had stated that he sent letters to Diana every day because of the guilt he felt for not visiting her.

When he was eighteen, he had Diana placed in a mental institution. Still, Reid knew that the way his mother was living wasn't healthy. Reid grew up learning nearly everything he knows from books, with his mother (a college professor of 15th-century literature) often reading to him. After waiting for all the other teenagers to leave, he walked home, only to find that his mother had not noticed he was so late to return because she had been having one of her schizophrenic episodes (" Elephant's Memory"). Reid once mentioned that he was a victim of bullying in school where he was stripped naked and tied to a goalpost in front of other students. In his youth, his father left him and his mother as he could no longer deal with her paranoid schizophrenia, among other things. He graduated from high school at the age of twelve. Spencer Reid was born on Octoto William Reid and Diana Reid.
