Here are some of the latest health and medical news developments, compiled by the editors of HealthDay:

Missouri Democrat Joins Fight Against Health Care Law

In a break with his political party, the Democratic attorney general of Missouri has filed a court brief asking a federal judge to overturn the new U.S. health law's requirement that most Americans obtain health insurance.

Attorney General Chris Koster took the action Monday following months of pressure from state Republicans. Koster is a onetime Republican state legislator who became a member of the Democratic Party in 2007, The New York Times reported.

Instead of joining attorneys general from other states who have taken legal action against the new health law, Koster filed a "friend of the court" brief, or legal argument, in the Court of Appeals for the 11th Circuit in Atlanta.

That appeals court is hearing a case filed by Republican governors and attorneys general from 26 states. In his ruling on the case, a federal district judge said that the entire health reform law should be invalidated but stayed his ruling until the matter was settled by the Supreme Court, The Times reported.

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Older Parents Happier: Study

People over the age of 40 who have children are happier than those over 40 without children, while those under 30 with children are less happy than those under 30 who are child-free, according to a new study.

American and German researchers analyzed self-reported levels of happiness among more than 200,000 people in 86 countries who took part in the World Values Surveys, The New York Times reported.

The study, published in the March issue of the journal Population and Development Review, doesn't reveal why parenting seems to be more enjoyable for people over 40.

The researchers also found that having more children makes older parents even happier, but makes younger parents unhappier, The Times reported.

For people under 30, those with two children are unhappier than those with one child, who are unhappier than those with no children. For parents over 50, each child brings more happiness. For parents ages 40 to 50, the number of children has no effect.

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No New Heart Warnings for ADHD Drugs: FDA

No changes in safety instructions or in the use of medicines to treat attention deficit hyperactivity disorder (ADHD) are being recommended by the U.S. Food and Drug Administration after receiving preliminary findings from an analysis of a huge amount of data, National Public Radio reported.

Currently, labeling for the drugs warns that misuse "may cause sudden death and serious cardiovascular adverse events."

The analysis, funded by the FDA and the federal Agency for Healthcare Research and Quality, included data from more than 500,000 people taking ADHD medicines and one million people who weren't taking the stimulant drugs, NPR reported.

There have been concerns about the safety of ADHD medicines since the release of a 2009 federal study that suggested a link between the drugs and sudden cardiac death in otherwise healthy young people. The study was published in the American Journal of Psychiatry.

At the time, the FDA pointed out a number of limitations with the study and said parents should not stop their children's use of the drugs. But the agency also promised further investigation into the issue, NPR reported.

The preliminary findings were originally due in late 2009 but the analysis took far longer than expected.

"At this time, FDA is not recommending any changes to the drug labels and/or the use of these medications," the agency said in a statement. "FDA will update the public after the results of the final analyses are evaluated."

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