The only child of William and Diana Reid, Spencer was born in Las Vegas, Nevada in the early Eighties. When he was ten, his father left the family, claiming he could no longer deal with Diana's paranoid schizophrenia. Of course, Diana begged him to take Spencer with him, but he refused, and with a just a simple 'good bye', he left.
It was commonly believed, especially by Spencer, that he left because he couldn't deal with Diana's illness. In fact, it was because he couldn't deal with the stress that came about when Diana witnessed a neighbor of theirs kill a man, because the man had killed the neighbor's son, and had gotten blood on her clothes when she had gone to see what had happened. William burned the clothes and Reid discovered later that said man who had been murdered might have been eying his four-year-old self as a potential victim.
In turn, this left Spencer to deal with it instead, by looking after and taking care of his mother when she needed it (such as reminding her to take her medication and to go to the doctor's). This caused him to become the primary caregiver to his mother, and in turn, end up devoting most of his time not in school to properly supervising her.
A shy and sometimes reserved child, he grew up learning much of his vast knowledge from books, some of which his mother often read to him, as she was once a professor of 15th century literature before her illness took hold. Spencer graduated from high school at the age of 12 and went on to college at Cal Tech. He ultimately earned three doctorates in Engineering, Chemistry and Mathematics and two bachelor degrees in Psychology and Sociology (and is working on a third, in Philosophy).
He also spent much of his childhood being bullied. When he was in high school, he was lured to the football field by one of the prettiest girls in school, only to be stripped naked and tied to the goalpost, while several others watched. He was left there for hours, until he managed to free himself and make it home. His mother never noticed him missing, because she was going through one of her episodes at the time.
When he turned eighteen, he has his mother committed; recognizing that he was unable to help her as she was and that the way she was living was unhealthy. He had her committed to Bennington Sanitarium, where she still is to this day.
At some point in his late teens/early twenties, he decided to join the FBI, after having gotten an exemption from the age requirement, and was, in turn, recruited by Jason Gideon, a living legend in profiling circles and one of the founders of the Behavioral Analysis Unit (henceforth known as the BAU), for the BAU. Spencer became an agent by the age of twenty-two, and the BAU is his first, and so far only, assignment.
For the most part, the role of the BAU is give their input on crimes that they've been invited in on, to see if they can profile the perpetrator (UnSub in FBI lingo, which is short for unknown subject), by looking at his crimes, his victims, his methodology to see what common grounds there are and to piece together an idea of the UnSub's psyche, which, in turn, gives the local law enforcement something to work with and give them an idea of the type of person that they would be looking for. This includes: visiting the crime scenes, investigating the victim (if it's recent) and viewing crime scene photos, interviewing friends/family and pretty much getting down and dirty with the details of the case. Reid's specialties are usually geographic profiles and the linguistic profile: figuring out the UnSub's comfort zone and their use of language and the clues that it might give into the mind of an UnSub.
Reid's team, in and of itself, has been considered one of the best the BAU has to offer. Lead by Unit Chief Supervisory Special Agent Aaron Hotchner (also known as the Team Mom), it also consists of SSA Jason Gideon, the Team Dad; SSA Derek Morgan (Reid's close friend who is like the big brother he never had); Special Agent Jennifer Jareau, or JJ, the team's Press Liaison, who is like a sister to Reid; Penelope Garcia, the team's technical analyst and Goddess of all things Computer and Photoshop; SSA Emily Prentiss, a fellow Profiler and someone Reid is close to; SSA Elle Greenaway, someone who was newer to the team then Reid and who was a friend until her burnout and replacement by Emily and SSA David Rossi, a mentor different from Gideon, but who took over the Team Dad role after Gideon's unexpected departure.
Of course, not all cases go smoothly for any of those involved and Reid is, by no means, without exception.
Such was one case in Georgia, where the team was called in to investigate a case where it seemed two UnSubs were killing people in the name of Religious Righteousness. It turned out that what they thought was two UnSubs, ended up being one, with multiple personalities: Tobias Hankel, his father and the archangel, Raphael.
After being kidnapped by Hankel, Reid was tortured over the course of two days (part of this was streamed over the internet to Hankel's computers back at his home, where the BAU was camped out, trying to figure out where Tobias took Reid). The personality of Tobias' father, Charles, was the one that tortures Reid, who, at one point, suffered a seizure and 'died', and Tobias ended up arguing with the other personalities in order to save him and succeeded, giving Reid CPR (this was all watched, of course, by the BAU back at Hankel's). Tobias also injected Reid with a drug called Dilaudid which, when cut with a powerful narcotic, caused Reid to flashback to his childhood: his father leaving and committing his mother.
The personality of Raphael was the one that continuously forced Reid to choose who would live and who would die, usually while playing Russian roulette with a handgun, even forcing him to choose a member of his team to die - Reid ended up choosing his unit chef, Aaron Hotchner, calling him a 'classic narcissist' and misquoting a Bible verse, which is what tipped Hotch off to the fact that Reid was attempting to send them a clue to his whereabouts. This is what ultimately led to the team figuring that he was being held in a graveyard on an abandoned plantation.
Towards the end of his captivity, Raphael finally got that confession of his sin he had been looking for and Reid was forced outside to dig his own grave. During this was when the team and the local law enforcement arrived, and during the distraction, Reid managed to take Hankel's gun and shoot, killing him.
After wards, Reid had some difficulties coping with what happened, telling fellow teammate Derek Morgan that he couldn't look at crime scene photos without identifying with the victims and knowing what it's like to know that you're about to die. It also seemed as if he was suffering from PTSD, as he had issues with loud noises of construction and became short and hostile with Emily, the newbie to the team who ended up replacing Greenaway when she left due to burnout (and the questionable shooting of an UnSub due to her own issues with PTSD).
He also suffered from an addiction to Dilaudid, which he didn't come to terms with until a case down the line in New Orleans, a missed plane and a talk with a friend of his named Ethan and later, with Gideon, about his struggles and his worries about the job. He missed a plane on purpose to see what would happen and after, tells Gideon that he will "never miss another plane again."
Shortly thereafter, Gideon suffered his own crisis of conscious and burn out. Of course, instead of just informing everyone, he instead skipped out, and when a worried Spencer goes to check on him, he found Gideon's empty cabin, his credentials and service weapon and a note… addressed to Spencer. The letter left Spencer with more questions then answers, but in the end, it showed that Spencer is inherently stronger then his mentor, overcoming challenges and using them to better his work and himself. This does nothing to help with his abandonment issues , but he finds a sort of replacement in the new Team Dad, David Rossi, a retired BAU agent brought back into the fold to replace the now MIA Gideon.
Reid has even been attending a meeting of the Beltway Clean Cops, pretty much NA for law enforcement, implying that he'd been getting help for his addiction, even though the reason he had been at the meeting was due to the fact that he had been craving again due to the aftermath of a case in which he was unable to talk down a victim's father from brutally shooting the UnSub while the UnSub was begging for his life.
The case following the meeting didn't help much with battling the cravings, when they were sent to Texas to investigate what they believed was a terrorist threat that took out a man and two policeman, only to discover that it was one of the policeman's sons, Owen Savage, who they discovered was an injustice collector, righting the wrongs committed against him and his girlfriend, Jordan. This included their fathers and fellow classmates, whom Owen gunned down because of hazing and bullying. Reid identified with the victim, to the point where Hotch had to order him back to Owen's house instead of on interviews, because he became hostile towards those who should have helped Owen instead of allowing things to continue.
In the end, Reid managed to talk Owen down even when the kid attempted suicide by cop, but Reid did it sans vest and in front of an entire police station of cops with their guns trained on Owen. Following this, on the plane ride home, Hotch questioned his motives, to which Reid answered that it was "his turn to save one." Hotch reminded him that it doesn't work that way, told him that another instance like that would get him fired, and he should go home and finish 'his movie' (one of the only instances that acknowledge that the team might know of his addiction).
He was so serious about not giving into the temptation that he refused drugs when infected with anthrax. It's also understood that a good portion of the team (or, at the very least, Gideon and Hotch) either knew of his addiction, or at the very least, knew something was wrong. It was one of those things that were left unspoken. At the point he's taken from, he's been clean for over a year.
Not long after the anthrax episode, the team ended up investigating a grueling case in Canada involving numerous missing homeless people and a pig farm, wherein Reid made the comment that pigs will eat anything, "and by anything, I mean, anything."
It's after returning home from that case, falling asleep in his own bed, that he wakes up someplace he doesn't recognize.
Reid is awkward and shy, which probably stems from his childhood experiences not only with his mother, but with the fact he was bullied in school as well. He's been known to tell people that "being the smartest kid in the room is also like being the only kid in the room." While his mind tends to function on a level that most do not understand, his social skills, on the other hand, have been described as being something like a student in middle school, while he dresses if he's attending prep school.
He suffers from abandonment issues when it comes to father figures: first his own, and then Jason Gideon, who left the BAU without notice following a rather bad case involving the death of Sarah (a woman who was important to him), seemingly disappearing and leaving a note at his cabin, addressed to Spencer, that was found when Reid went to the cabin to check on his mentor.
There are times when the others have to quiet him when he starts off on something that he fixated on. He's also been known to unintentionally and unknowingly change the subject of the conversation and usually a team member either guides him back to what they were discussing or he gets cut off with a "Reid." It has been speculated by the actor who portrays Reid that he has shades of schizophrenia or a minor form of autism, such as Asperger's Syndrome. It's also almost seems like he has a knack for having a statistic for any given situation. It has also been noted that Reid also has shades of obsessive compulsive disorder and is a germophobe, which is one of the reasons he tends to raise a hand in greeting or wave, instead of shaking hands.
And while he tends to show some sort of ineptness when it comes to the ladies, as he gets nervous and starts sprouting off facts and statistics, there have been a couple that he's managed to have a conversation with: Lila Archer, an actress that he had been assigned to protect and had to pull him into the pool and start making out with in order for him to see that she liked him and a bartender that he was talking to during another case, in which he wooed her with Magic (that he used on the advice on Morgan) while talking to her and showing her a sketch of a potential UnSub. Then again, most of the time when he does get hit on, it tends to go WAY OVER his head, such as with prostitutes who apparently proposition him every time they are questioned.
Reid's good at reading maps, and as such, he's usually the one working on a geological profile. He's also a linguist, looking for the meaning behind words to find the clues held within. He tends to read government reports, so he knows the busiest span of highway in America, even if it's over a thousand miles from home.
Reid suffers from a guilt complex, seen in the fact that while he knows he had to commit his mother, he still feels bad about it and as such, writes her a letter every day, and also seen when it comes to a case involving an UnSub named Adam Jackson, who, it turned out, had another personality, Amanda, who wound up taking over in the end. Reid kicked himself for not seeing it, as he had experience with this sort of thing before, ie, Tobias Hankel in Georgia. As a matter of fact, he still regularly visits Amanda, hoping to still find Adam somewhere locked inside.
He is also scared about the possibility of inheriting his mother's illness. He knows that schizophrenia can be genetically passed down and has commented to his teammates that he "knows what it's like to be afraid of your own mind," and that he "knows what the voices are like."
He has abandonment issues when it comes to father figures: first his own, and then had them compounded by Jason Gideon. While Gideon might not have been his real father, he was something of a father figure for him, having guided Reid in his growth of becoming a Profiler and helped shaped him into the man and agent he is today.
However, said issues do not keep him from seeing the team as some sort of makeshift family. JJ makes him the godfather of her child, Henry, for example, and Garcia and Morgan tend to fuss over him like older siblings. Morgan even calls him 'pretty boy' while JJ usually refers to him as 'Spence'. Gideon and Hotch (and later, Rossi, after Gideon's departure), are often seen as the team parents. Gideon even started the trend of making sure, when introducing Reid to anyone, to always introduce him as Doctor Spencer Reid. When Reid questions this, Hotch explains that it's because Gideon didn't want people to just see him as a kid, but as someone who should be treated with respect.
Reid also has his share of quarks as well: he likes to wear mismatched socks and his watch over his shirt sleeve. He drinks coffee like it's water, it has been speculated by his teammates that it's just sugar with a coffee flavoring. He's also afraid of the dark, as it's the inherent absence of light and also had suffered from nightmares due to the nature of their job. Not to mention, despite all the things that he can do, Reid cannot use chopsticks despite the other's best efforts in trying to teach him ("it's like foraging with number two pencils") and while he does know how to use a computer, he tends to stick with the old fashioned way of doing things, preferring pen and paper over a computer screen and a keyboard.
To put it mildly, Reid is a genius. He has an IQ of 187; has an eidetic memory and can read over 20,000 words a minute. Not to mention, he has also been referred to, more then once, as the team's living computer.
By his own admission, he does his best work while under stress (usually at the threat of his own or someone else's life) and while he tends to have trouble passing his firearms qualification, he's a damn good shot when lives are in danger (he's killed two UnSubs). It also doesn't seem like his memory always extends to what he hears, as he did have trouble remembering Penelope Garcia's name when Morgan asked for it. He's damn good at reciting all the random things he's ever read and then some, though.
It's implied that he knows different languages (in season 5, JJ asks him if he reads anything other than technical manuals, he answers 'not in English'), isn't up-to-date on pop culture (or, at the very least, popular tween/teen culture, he didn't know what 'Twilight' was and he's not well versed in net lingo: "What's BFF?"), he's usually the one that colors in the maps and work out a geographical profile, he's also a linguistic profiler, as he also looks through communications left by the killers for any clues or hints and pieces them together to further develop the profile as he has a way with words.
Important relationships and connections.