Cyberonics Inc.‘s online advertisement for its device to treat depression is misleading and makes exaggerated claims about how well it works, a U.S. advocacy group said on Thursday.

The ad, which is running on WebMD Health Corp.‘s WebMD Web site, makes at least 10 false claims about its vagus nerve stimulation (VNS) device violating U.S. regulations, Public Citizen’s Health Research group said in a letter to the Food and Drug Administration.

It should be immediately withdrawn, and a corrective ad should also be run in its place, the group added.

Cyberonics Chief Executive Officer Robert “Skip” Cummins did not have specific comment on the ad or letter, but said the company ensured its marketing met certain standards.

“All of our marketing and educational materials go through a rigorous compliance process to ensure that all communications with medical personnel and consumers are fair and balanced and comply with all laws and regulations,” he said in an e-mailed statement.

Shares of the Houston-based company hit a new 52-week low on Thursday, closing down 2.8 percent, or 58 cents, to $20.07.

Vagus nerve stimulation involves a pacemaker-like device that sends mild pulses to stimulate the left vagus nerve in the neck, Cyberonics said in its ad, posted online at http://www.webmd.com/content/pages/25/113832.htm.

The company said that with the therapy, the vagus nerve delivers pulses directly to the areas of the brain that affect mood and other symptoms of depression.

Public Citizen said the company, in two paragraphs in the ad, overstated the number of patients who could be evaluated in studies and excluded some results, among other problems, Public Citizen said.

The ad also failed to mention that the device was for those with treatment-resistant depression with no success from other therapies, the letter said.

“The point is that the company has cherry-picked which studies to cite on the Web site” and avoided mentioning negative results from the best-designed trials, the group wrote. “This selective presentation of results in the advertisement ... is misleading to physicians and patients.”

FDA approved the controversial use of VNS Therapy last year, but questions have been raised over whether top FDA officials ignored staff reviewers who said evidence to support wider use was weak.

Senate Finance Committee Chairman Sen. Charles Grassley, an Iowa Republican, has been investigating the case while Public Citizen and other critics have said there was never enough evidence to show the device was safe and effective.

“This device should never have been approved, but, as long as it still is, it is time for the FDA to step in and make sure the device is legally advertised,” the group’s letter said.

Separately, some analysts have said the company’s massive marketing push is not convincing doctors to use VNS for their patients with depression.

Lazard Capital Markets Alexander Arrow, whose firm is a market maker in Cyberonics’ shares, urged investors to sell the devicemaker’s stock before the American Psychiatric Association’s annual meeting next week in Toronto.

“We believe the response of psychiatrists at their biggest meeting of the year to vagus nerve stimulators will be more like mixed ambivalence than enthusiastic receptivity, despite Cyberonics’ massive marketing push,” Arrow said in a research note.

Cyberonics will be sponsoring at least one discussion at the meeting. Arrow said the events may be well attended by supporters of the device but were unlikely to “significantly sway opinion.”