At the beginning of Calypso, an odd verbal mannerism characterizes Bloom's concern for getting his wife's breakfast plate exactly right: "Another slice of bread and butter : three, four : right. She didn't like her plate full. Right." At the beginning of Hades, a similar, and rhyming, repetition characterizes his need to make sure that the carriage door has latched tight: "He pulled the door to after him and slammed it tight till it shut tight." A psychologist might speculate that Bloom suffers from a touch of obsessive-compulsive disorder.
OCD is not a new diagnosis. The British term "obsession" and the American term "compulsion" both started as translations of the German word Zwangsvorstellung ("forced ideas," i.e. compulsive ideation), coined in 1877 by neurologist and psychiatrist Carl Westphal. (Westphal also invented the term agoraphobia, and made several other important medical discoveries, including the first clinical descriptions of narcolepsy and cataplexy. According to Michel Foucault, he originated the modern idea of the homosexual.)
A decade earlier, in 1868, the neurologist and psychiatrist Wilhelm Griesinger published three case studies of a neurosis that he called Grübelsucht (meaning something like "brooding-searching" disorder). Many French, German, and Austrian psychologists of the 19th and early 20th centuries sought fitting language to investigate the nature and causes of obsessive thoughts and actions. Identification of the problem began still earlier. A web article posted by the Stanford University School of Medicine cites instances from the 17th century, including one from Ireland: "In 1660, Jeremy Taylor, Bishop of Down and Connor, Ireland, was referring to obsessional doubting when he wrote of 'scruples': '[A scruple] is trouble where the trouble is over, a doubt when doubts are resolved'" (see http://ocd.stanford.edu/treatment/history.html).
In 1888 the Irish expert on mental disorders whom Buck Mulligan mentions in Telemachus gave a talk titled "A Rare Form of Mental Disease (Grübelsucht)," which was later published under his name and occupation: "Conolly Norman, M.K.Q.C.P., F.R.C.S.; Medical Superintendent of the Richmond District Asylum, Dublin." Norman refers to Griesinger's 1868 publication and notes that the illness "has no recognised designation in English." He translates the old verb grübeln as "to go about inquiring, to inquire closely, to busy oneself inquiring about subtle questions or trivial matters, to pry," and says that the essential feature of the disease is "the obsession of the mind by an imperative mode of thought, taking the form of perpetual interrogation, a constant urgent morbid impulse to inquire into and investigate everything, an incapacity to accept contentedly the ordinary postulates of knowledge." Many of these questions, he notes, are "of an entirely unpractical and untheoretical nature; but this is not necessarily so." He cites the case of a woman who, when she woke up, experienced dread of what would happen if she did not get out of bed immediately. She felt "compelled to examine any bit of straw or paper or glass that she saw. In the street she must find out what any scrap of written or printed paper was and to what it referred." A taste of soup sent her into loops of questioning whether or not thyme was one of the ingredients, and whether some of her sips were in fact detecting thyme or some other spice, and what thyme really is, and so on.
Diagnosing mental diseases in literary characters and dead authors is an intellectually suspect, and frequently frivolous, enterprise. But Joyce was interested in late 19th century psychological theories. In Circe he applied some of the theories of the "sexologists" (Richard von Krafft-Ebing, Havelock Ellis, Sigmund Freud) to the understanding of Bloom's neuroses, no doubt performing some psychoanalysis on himself as he wrote. It may be worth asking whether the author connected Bloom's incessant questioning with a morbid tendency to overthink the smallest details of daily life.