Possibly, but probably not. But Jesus more likely was, and many of the T'ang Dynasty Zen Master almost certainly were.
Now, before anyone gets upset (if it's not already too late), I don't mean anything derogatory by the term "schizophrenic," and will use the symptomatic term "schizotypal" rather than the diagnostic term "schizophrenic," which is to say I don't know whether they were schizophrenic or not (not only an I not a psychiatrist, but they all lived hundreds to thousands of years ago). But they certainly did display schizotypal symptoms.
Individuals with schizoid personalities are said to have little capacity for close relationships and are also eccentric in their behaviors, perceptions, and thinking. According to the DSM-IV manual, the following symptoms are considered schizotypal:
A. Ideas of reference (excluding delusions of reference)
B. Odd beliefs or magical thinking that influences behavior and is inconsistent with subcultural norms (e.g., superstitiousness, belief in clairvoyance, telepathy, or “sixth sense”; in children and adolescents, bizarre fantasies or preoccupations)
C. Unusual perceptual experiences, including bodily illusions
D. Odd thinking and speech (e.g., vague, circumstantial, metaphorical, overelaborate, or stereotyped)
E. Suspiciousness or paranoid ideation
F. Inappropriate or constricted affect
G. Behavior or appearance that is odd, eccentric, or peculiar
H. Lack of close friends or confidants other than first-degree relatives
I. Excessive social anxiety that does not diminish with familiarity and tends to be associated with paranoid fears rather than negative judgments about self.
Jesus certainly displayed symptoms B though D, and although many now believe his claims of divinity to be true does not mean that they weren't "odd" or "unusual" at the time. They certainly garnered him a lot of attention. He prophesied that he would be betrayed and martyred, which fits symptom E (even though he eventually was in fact betrayed and martyred, even paranoids, as they say, have enemies). His outburst at the Temple, turning over tables and chasing out the merchants, qualifies for G. The fact that his closest associates, the 13 Disciples (later 12), reportedly included thieves, tax collectors, and other social outcasts suggests that he had somehow alienated the friends and colleagues he must have developed during the largely undocumented, early part of his life (symptom H).
Now, saying that Jesus may have exhibited schizotypal symptoms does not in any way take away - or support - any faith-based claims about him. I'm not saying that he was delusional or insane, just that his neural wiring was apparently different from the norm. . . which is exactly what one would expect of a messiah in human form. I'm not attaching any stigma to schizotypal symptoms, I'm just calling them what they appear to be.
The Buddha rejected any claims of divinity, and urged his followers to look within themselves for their answers. He even resisted notions of himself as the leader of a spiritual system, and the fact that a thing called "Buddhism" now exists can be viewed as a failure on the part of the Buddha to stop people from viewing him in that way. But to be fair, it can certainly be claimed that the Buddha exhibited symptoms B, C, and D to some extent or another. His celebrated calmness and passivity may qualify as the "constricted affect" of symptom F.
On the other hand, though, the Masters of the T'ang Dynasty "Classical Period" of Zen behaved very strangely indeed. Specifically, I'm talking about post-Hui-Neng Masters such as Nangaku, Baso, Nansen (who once sliced a cat in half to make a point), Joshu (who put his sandals on his head in response to Nansen's cat-killing), Hyakujo, Gutei, certainly Rinzai, and even Layman Pang, and so on down the line.
The Zen koans, the so-called "inscrutable puzzles" of Zen, are by and large examples of the bizarre exchanges of the Classical Period Masters with their students and with each other. When seen from the perspective of the awakened mind, their words and actions, although still not "logical," are understandable and even appropriate, but as seen from the norms of society, the perspective from which clinical psychologists practice today, their thinking, speech, and actions were certainly "odd" and "unusual." Their behaviors were erratic and often semi-violent, and many koan stories culminate with blows to the head and twisted noses. Gutei even cut off a disciple's finger once to make a point. Reading the koan stories without an understanding of awakening is often like reading a script for The Three Stooges as authored by Kafka and Beckett.
During the subsequent Song Dynasty, the Zen Masters typically did not engage in such eccentric behaviors, and Zen entered the so-called "Literary Period" where the Masters studied and taught using the recorded words and actions of their predecessors, rather than engage in such acts themselves. Did the Song Dynasty have different ways of dealing with schizotypal personalities that the T'ang Dynasty, or was the change of behavior from one dynasty to the net merely coincidental?
Just like when talking about Jesus, though, I don't mean to imply that the actions of the earlier Masters were delusional or merely the unfortunate results of a mental illness. My point is that when viewed from the clinical perspective of societal norms, the actions of saints and sages through the centuries, including the T'ang Dynasty Zen Masters and, yes, Jesus, were certainly "unusual" and would qualify as some, if not most, of the DSM symptoms.
The American neuroendocrinologist Dr. Robert Sapolsky has theorized that a schizotypal gene exists and has been passed down over the generations from the ancients to the present. Interestingly, Dr. Sapolsky theorizes that the vast majority, if not all, of the saints and sages throughout history probably carried the gene, which leads to the question of whether or not the trait carries the genetic advantage of providing society with shamans and seers to provide spiritual comfort to society. He goes on to cite tribes that always seem to have one erratic or bizarre member who serves as the shaman or medicine man or prophet to help guide the tribe and provide some measure of solace when confronting the inexplicable. Since so many tribes and societies across the world all tolerate, even celebrate, one otherwise non-productive individual in their midst, there must be a functional purpose for both that individual and for the gene that influences that individual's behavior.
Seen in this light, then, the schizotypal symptoms are not seen as an illness or a sign of delusion, but an indication that the individual has the same shaman gene as the seers and prophets throughout history, a gene that may allow the individual to see beyond the mundane world of the relative and into the absolute. I wouldn't go so far as to say that every schizophrenic is a seer or that every seer is a schizophrenic, but I'm saying that there may be a behavioral, and possibly a genetic, link between the two.