Allergan Inc. (AGN)’s wrinkle treatment Botox, approved in the U.S. for preventing chronic migraines, provides only modest relief for patients with the headaches, an analysis of previous studies showed.

A new review of research published in the Journal of the American Medical Association found that Botox had no benefit for those with episodic migraines that occur less than 15 times a month, or chronic tension headaches that occur more than 15 times a month. The analysis also showed that Botox reduced chronic migraines and daily headaches by only about two per month.

Migraine headaches can cause intense throbbing or pulsing in the head and is commonly accompanied by nausea, vomiting and extreme sensitivity to light and sound. Chronic migraine sufferers are defined as people who suffer from headaches on 15 or more days per month. Episodic sufferers are those who suffer from headaches for fewer than 15 days.

Patients who started out having headaches almost daily reported two fewer headaches per month when they were given injections of botulinum toxin A. They also had more side effects, including weak muscles and a stiff neck.

The analysis found that Botox cut the number of chronic migraines per month to 17.2 from 19.5 and reduced chronic daily headaches to 15.4 from 17.5 on average.

Since Botox has become a popular way to eliminate wrinkles in the forehead, doctors have been using it for all types of treatments, from excessive sweating to headaches.

The U.S. Food and Drug Administration approved Botox as a treatment for preventing chronic migraine headaches in 2010, but so far literature on its effectiveness has been mixed.

According to a report by the Washington Post, even as Democrats seek the biggest expansion of health coverage in decades, as many as 23 million people could still be without insurance by 2018, illustrating the complexity of achieving the long-held Democratic goal of universal health care.

The legislation that the Senate passed Christmas Eve, which is expected to resemble closely the final bill that is hashed out between the House and Senate over the next month, would leave about 8 percent of the population under age 65 without health insurance, according to the nonpartisan Congressional Budget Office. It would extend insurance to 31 million of an estimated 54 million who would have no coverage without the legislation.

Those who would be left uninsured have drawn little attention,in part because their ranks would include many who choose not to get health insurance, even though they can afford it — such as some healthy people under 30, who have little effect on rising health-care costs because they rarely go to the doctor. Though starting in 2014, individuals would face fines if they do not buy coverage, some may still refuse, reports the Post.

Americans are worried about hidden costs in the fine print of health care overhaul legislation, an Associated Press poll says.

That’s creating new challenges for President Barack Obama as he tries to close the deal with a handful of Democratic doubters in the Senate.

Although Americans share a conviction that major health care changes are needed, Democratic bills that extend coverage to the uninsured and try to hold down medical costs get no better than a lukewarm reception.

The poll found that 43 percent oppose the health care plans being discussed in Congress, while 41 percent are in support. An additional 15 percent remain neutral or undecided.