About 200 million people around the world use illicit drugs, according to a study published on Friday in The Lancet.

It estimates that in 2009 between 149 and 271 million people used an illegal drug.

Cognitive skills can start to fall from the age of 45, not from around the age of 60 as is commonly thought, according to research published on Friday by the British Medical Journal (BMJ).

Researchers led by Archana Singh-Manoux from the Centre for Research in Epidemiology and Population Health in France and University College London observed 5,198 men and 2,192 women over a 10-year period from 1997.

Advances in fertility treatment and a trend toward later-life childbirth are fueling a boom in twins in the United States, where one in 30 babies is a twin, according to U.S. data out Wednesday.

The number of twins doubled in 2009 compared to 1980, rising from 68,339 to over 137,000 births, said the National Center for Health Statistics' data brief on three decades of twin births in the United States.

A man left unable to walk by a tumor on his right leg that weighs more than the rest of his body went under the knife in Vietnam on Thursday to have the growth removed, hospital officials said.

Nguyen Duy Hai's massive 90 kilogram (198 pounds) tumor is to be cut away by a team of doctors in a risky 10 hour procedure that has only a 50 percent chance of success, the France-Vietnam(FV) hospital in Ho Chi Minh City said.

Colombia will pay for the removal of defective French-made breast implants for patients whose doctors recommend it, the health ministry has said, responding to a growing global scare.

"There is no mass recall statement from the ministry," Deputy Health Minister Paula Acosta said at a news conference on Wednesday, referring to the implants, which were made with sub-standard industrial-grade silicone.

People who eat too much of a high-calorie, low-protein diet tend to gain more body fat than people who overeat high amounts of protein, U.S. researchers said Tuesday.

A study published in the January 4 issue of the Journal of the American Medical Association included 25 people in Louisiana who agreed to live as in-patients in a weight-gain experiment for a 56-day period.

Obese people who undergo gastric bypass surgery are less likely to die from heart attack and stroke than people who receive more conventional treatment for their weight condition, a Swedish study said Tuesday.

The study, published in the January 4 issue of the Journal of the American Medical Association, included about 4,000 patients in Sweden who were recruited between 1987 and 2001.

France vowed Tuesday to probe failures to detect faults with the French-made breast implants at the center of a health scare, as a supplier confirmed selling non-standard silicone to their manufacturer.

A growing litany of accusations against now-defunct Poly Implant Prothese (PIP) has triggered a worldwide scare with several countries, including France, advising thousands of women to have its implants removed.

Check-ups during pregnancy tend to focus around the waist. But there's growing debate about which mothers-to-be should have a gland in their neck tested, too.

Numerous studies since 1999 have found that an underactive thyroid can raise a woman's risk of miscarriage, premature birth, or a lower IQ for her baby — even if it's so mildly sluggish that she feels no symptoms.

Massive disinfection work was carried out at Hong Kong's new government headquarters Tuesday, after the bacteria of a potentially fatal disease was found and one minister was hospitalized.

Health authorities said nine water samples taken from various sites in the buildings, including the chief executive's office, tested positive for Legionella, which causes Legionnaires' disease, a severe form of pneumonia.