Chiropractic theory is rooted in the notions of Daniel David Palmer, a grocer and "magnetic healer,” who postulated that the basic cause of disease was interference with the body's nerve supply.

In 1910, he wrote that “a subluxated vertebrae . . . is the cause of 95 percent of all diseases. . . . The other five percent is caused by displaced bones other than those of the vertebral column." He proclaimed that subluxations interfered with the body's expression of "Innate Intelligence"—the "Soul, Spirit, or Spark of Life" that controlled the healing process. He proposed to remedy the gamut of disease by manipulating or "adjusting" the problem areas.

Over the years, most chiropractors have given up Palmer's theories, although some still cling to them. Some describe subluxations as "bones out of place" and/or "pinched nerves"; some think in terms of "fixations" or loss of joint mobility. Some occupy a middle ground that includes any or all of these concepts. And some say—correctly—that Palmer's notions were biotheistic nonsense.

Chiropractic schools provide a similar spectrum of beliefs. Some reject Palmer’s views outright. A few still teach them literally. Others occupy a middle ground by asserting that chiropractic has become more scientific, but they still expose their students to “chiropractic philosophy” for historical reasons.

In line with this philosophy, many chiropractors urge people to have “preventive maintenance” in which a person’s spine is periodically checked for subluxations and “adjusted,” even if they have no symptoms. Some chiropractors encourage these practices from birth onward.

In 2000, researchers surveyed 658 chiropractors in the U.S. and reported that 79% recommended periodic maintenance care and 34% of their patients complied. The article also noted that 90% of the chiropractors agreed or strongly agreed that optimizing health was one of the purposes of maintenance care. The researchers estimated that income from “preventive and health-promoting services” averaged $50,000 per chiropractic practice in 1994 and was exceeded only by their treatment of back pain. In 2002, when 1,100 chiropractors in North America were asked by mail whether their clinical routine included periodic maintenance or wellness care, 94% of the 638 who responded said they did.

Contracts for long-term care add another dimension to the problem. Thousands of chiropractors offer contracts under which patients pay in advance or agree to pay for multiple visits at a discounted price. I have seen contracts for as many as 100 visits. Chiropractors who offer them typically tell all patients that long-term care is needed to prevent recurrence, spinal degeneration, or various serious diseases. Some chiropractors display a chart of "subluxation degeneration" or "spinal decay" that they say is inevitable without intensive, long-term care.

All such advice represents overselling. Even if chiropractic treatment can legitimately help a problem, it is not possible to know in advance that a large specified number of visits will be needed. In most cases where spinal manipulation can help relieve pain, the relief comes quickly and there is no valid reason to continue when symptoms resolve. Pre-pay contracts are a hallmark of chiropractors who pressure patients to sign up for care they don’t really need. The precise amount of worthless “preventive” treatment sold by chiropractors is unknown, but my research suggests a conservative estimate of at least $1 billion per year.

A recent thorough investigation of the scientific literature found no evidence that chiropractic care can prevent or stop early disease. The researchers urged chiropractors to “cease such activities until, if ever, new evidence emerges.” It’s doubtful that chiropractors will follow this advice.

Stephen Barrett, M.D., a retired psychiatrist who resides near Chapel Hill, North Carolina, publishes quackwatch.org, chirobase.org, 23 other consumer protection websites, and Consumer Health Digest, a free weekly e-mail newsletter.