Not only did heavy marijuana smoking not appear to be linked with lung cancer in later life, but there was also no apparent link with other head and neck cancers, including those of the esophagus, mouth and throat.

The study was comprised of 611 people who had developed lung cancer, 601 who had developed cancers of the head or neck, and 1,040 without cancer who had been selected on the basis of age, gender and neighborhood. All of the subjects were under 60, as it was assumed that those born prior to 1940 would have been unlikely to have been regular consumers of marijuana in their teens and 20s, the time heavy consumption is most frequent.

Eighty percent of those with lung cancer and 70 percent of those with head and neck cancers had smoked tobacco, while approximately half of all patients with cancer had smoked marijuana heavily.

Heavy marijuana smokers were not found to have an increased risk of lung cancer over those who smoked tobacco; surprisingly, nor were they found to have an increased risk of lung cancer over moderate marijuana smokers and those who had never partaken of the drug.

Meanwhile:

-- One cigarette really is all it takes for children to become addicted to smoking, British researchers have found.

According to a study led by Jennifer Fidler, a research psychologist at University College London's Department of Epidemiology and Public Health, and published in the July issue of Tobacco Control, a single cigarette can act as a 'sleeper' inside a child, making them more likely to become a smoker in later life.

"Although it is known that past smoking behavior is associated with future smoking, this is the first time that a period of 'dormant vulnerability' has been shown, whereby smoking a single cigarette can leave children susceptible to smoking uptake for several years," Fidler said.

The study was conducted on 5,863 south London schoolchildren between the ages of 11 and 16. By age 14, children who had smoked a single cigarette at the age of 11 were twice as likely to be regular smokers as children who had abstained.

"This was despite a gap of up to three years, when no further smoking occurred," Fidler said.

"Preventing children from trying even one cigarette may therefore appear an important goal," she said.

"Another implication is that healthcare providers and those designing interventions should not ignore adolescents who appear to be long-term non-smokers but had tried smoking once several years ago. These children are at an increased risk of taking up smoking and may be missed in targeted interventions."

-- Obesity can be linked with poverty in teens aged 15-17, a new study by Johns Hopkins University's Bloomberg School of Public Health has found, but no similar correlation exists for those aged 12-14.

The study, published in the May 24/31 issue of the Journal of the American Medical Association, found that for teens aged 15-17, obesity rates were 50-percent higher for those living below the poverty line.

"Those who live in poverty are about 50 percent more likely to be overweight compared to those not living in poverty," said lead researcher Richard Miech. "Not only that, but one of our key findings is that this difference has emerged recently. In the '70s and '80s, there was no difference at all."

-- According to a study published by the Beth Israel Medical Center in New York City in conjunction with the National Institute on Media and the Family, surgeons may benefit from playing video games prior to surgery.

Surgeons who 'warmed up' for surgery by playing video games for 20 minutes before entering the operating theater were found to be faster, and to make fewer errors, than surgeons who did not.

The study, led by Dr. James Rosser, tested 303 surgeons on their performance at the "cobra rope" drill, a laparoscopic training exercise Rosser describes as "trying to tie your shoe laces with three-foot-long chopsticks while watching on a TV screen."

Surgeons who played video games prior to completing the training exercise finished the drill, on average, 11 seconds more quickly than those who had not. Errors in laparoscopic surgery lengthen the duration of the surgical procedure, so it follows that those surgeons who completed the task quickly made fewer errors than those who were slower.

-- At last, doctors have found an easy way to maintain weight: on your back, fast asleep.

A U.S. study of 70,000 women, called the Nurses Health Study, found that women who sleep too little -- five hours or fewer per night -- risk major weight gain, Britain's Daily Mail newspaper reported.

The study took place over 16 years, with doctors monitoring the women's weight and sleeping habits over that time.

Over the course of the study, women who consistently slept five hours or fewer per night were 32-percent more likely to have suffered significant weight gain (defined as 33 pounds or more over the 16-year period) than those who slept for seven hours.

They were 15-percent more likely to become obese.

Study leader Dr. Sanjay Patel of Case Western Reserve University in Cleveland, Ohio, said: "Prior studies have shown that after just a few days of sleep restriction, the hormones that control appetite cause people to become hungrier, so we thought that women who slept less might eat more.

"But in fact they ate less. That suggests that appetite and diet are not accounting for the weight gain in women who sleep less."

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