Use of antidepressant drugs in the United States doubled between 1996 and 2005, probably because of a mix of factors, researchers reported on Monday.

About 6 percent of people were prescribed an antidepressant in 1996 – 13 million people. This rose to more than 10 percent or 27 million people by 2005, the researchers found.

“Significant increases in antidepressant use were evident across all sociodemographic groups examined, except African Americans,” Dr. Mark Olfson of Columbia University in New York and Steven Marcus of the University of Pennsylvania in Philadelphia wrote in the Archives of General Psychiatry.

“Not only are more U.S. residents being treated with antidepressants, but also those who are being treated are receiving more antidepressant prescriptions,” they added.

More than 164 million prescriptions were written in 2008 for antidepressants, totaling $9.6 billion in U.S. sales, according to IMS Health.

A group of doctors in the UK are mounting a legal and political campaign to overturn the suicide verdict in the death of a British doctor who was found dead shortly after exposing falsehoods about the justification for the Iraq war.

Dr. David Kelly was found dead in 2003 in a forest near his home in Oxfordshire. An inquiry into his death concluded that he had bled to death during a suicide attempt.

But 13 UK doctors are now challenging that assertion — and in doing so, renewing suspicions the doctor may have been murdered after it was revealed he was the mole for a BBC report that said evidence used to launch the Iraq war had been “sexed up.”

He was intending to reveal that he warned Prime Minister Tony Blair there were no weapons of mass destruction anywhere in Iraq weeks before the ­British and American invasion. He had several discussions with a publisher in Oxford and was seeking advice on how far he could go without breaking the law on secrets.

Following his death, his computers were seized and it is still not known if any rough draft was discovered by investigators and, if so, what happened to the material.

Dr Kelly was also intending to lift the lid on a potentially bigger scandal, his own secret dealings in germ warfare with the apartheid regime in South Africa.

The World Health Organization warned on Wednesday that a global flu pandemic was imminent, raising its threat level as the swine flu virus spread and killed the first person outside of Mexico, a toddler in Texas.

“Influenza pandemics must be taken seriously precisely because of their capacity to spread rapidly to every country in the world,” WHO Director General Margaret Chan told a news conference in Geneva.

“The biggest question is this: how severe will the pandemic be, especially now at the start,” Chan said, but added the world “is better prepared for an influenza pandemic than at any time in history.”

Fears of a global swine flu pandemic grew with new infections in the United States and Canada on Sunday, and millions of Mexicans hid indoors to avoid a virus that has already killed up to 81 people.

While the only deaths have been in Mexico, the flu is spreading with 20 cases in the United States and six in Canada, and possible cases as far afield as Europe and New Zealand.