In the twelfth and thirteenth centuries, Scholastic theologians classified masturbation as an “unnatural” sexual sin, putting it into the same category as sodomy and bestiality, two of the most despised behaviors in Christian morality (Rice, n.d.). The stage was set for physicians later on (in the eighteenth century), when they began replacing clerics as the go-to authorities on sex, to transform masturbation from sin to sickness. Physicians did not simply claim that masturbation caused harm, they claimed that it led to the most severe forms of harm: paralysis, madness, idiocy, epilepsy, suicide, and cancer (Hare, 1962). One nineteenth-century physician proclaimed that “neither the plague, nor war, nor small-pox, nor similar diseases have produced results so disastrous” (Adam Clarke, quoted in Kellogg, 1881, p. 268). John Harvey Kellogg (1881), also a physician, held that masturbation was the “most dangerous of all sexual abuses” (p. 315). Not only were physicians, preachers, and common people taken in by these claims, but so were many of the great thinkers of the day. Asserting that all physicians had agreed, philosopher Jeremy Bentham (1978/1785) declared that, of all the sexual “irregularities,” masturbation was the “most incontestably pernicious” with “the most serious effects on health” and mental well-being. Philosopher Jean-Jacques Rousseau asserted that masturbation was equivalent to “mental rape” (Soble, 2003).

Medical professionals began believing in grave harm from masturbation after eighteenth-century physicians offered mechanistic explanations (e.g., the Swiss physician Tissot proclaimed that physical and mental debilities resulted from the loss of vital bodily fluids). Notably, all such explanations were conjecture—never tested, never verified, but nonetheless facilely absorbed into the medical field because of their moral resonance. With the pathology view in place, physicians cherry-picked anecdotes and unsystematic data for confirmation (e.g., mental asylum patients were seen to openly practice masturbation, so masturbation was assumed to have been the cause of their mental illness). In the meantime, physicians and self-proclaimed healers endorsed therapeutic quackery, including innocuous preventatives such as Kellogg’s Cornflakes and the Graham Cracker (claimed to counteract temptation through their blandness) and iatrogenic treatments such as chastity belts, electric shock, cauterization, blistering the penis with nitric acid, circumcision, and castration (Hodges, 2005).

Whorton (2001) held that the masturbation panic began to fade at the end of the nineteenth century, when certain physicians and other researchers set aside moral judgment and began thinking scientifically (e.g., was masturbation in asylum patients the cause or the effect of their mental illness; did asylum observations generalize to non-patients). Hodges (2005) noted that Kinsey’s research in the middle of the twentieth century, finding masturbation to be nearly universal among males, added weight to the argument that masturbation is not associated with disease. Hall (1992) noted that, in spite of any research done or scientific opinion offered, panic abatement was slow across the twentieth century, lasting well into the second half, and attitudes on masturbation seemed to transition into non-alarm and then approval only in relation to changing cultural ideologies (e.g., greater dominance of the progressive voice, which departed from traditional sexual morality). The argument here, then, is not that masturbation is seen more benignly today because science has triumphed over morality, but rather that the regnant morality that brought masturbation into panic has been contained and essentially removed from biasing the science as it considers this behavior going forward.

--Rind, "Sacred Values, Politics, and Moral Panic: A Potent Mix Biasing the Science behind Child Sexual Abuse and Related Phenomena" in Frisby et al eds, Ideological and Political Bias in Psychology (2023)