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A new study indicates that marijuana isn’t a painkiller, but a pain distracter: Under the influence of THC, the same levels of pain are simply less bothersome. Image via Wikimedia Commons/Cannabis Training University

One of the chief arguments for the legalization of medicinal marijuana is its usefulness as a pain reliever. For many cancer and AIDS patients across the 19 states where medicinal use of the drug has been legalized, it has proven to be a valuable tool in managing chronic pain—in some cases working for patients for which conventional painkillers are ineffective.

To determine exactly how cannabis relieves pain, a group of Oxford researchers used healthy volunteers, an MRI machine and doses of THC, the active ingredient in marijuana. Their findings, published today in the journal Pain, suggest something counterintuitive: that the drug doesn’t so much reduce pain as make the same level of pain more bearable.

“Cannabis does not seem to act like a conventional pain medicine,” Michael Lee, an Oxford neuroscientist and lead author of the paper, said in a statement. “Brain imaging shows little reduction in the brain regions that code for the sensation of pain, which is what we tend to see with drugs like opiates. Instead, cannabis appears to mainly affect the emotional reaction to pain in a highly variable way.”

As part of the study, Lee and colleagues recruited 12 healthy volunteers who said they’d never used marijuana before and gave each one either a THC tablet or a placebo. Then, to trigger a consistent level of pain, they rubbed a cream on the volunteers’ legs that included 1% capsaicin, the compound found that makes chili peppers spicy; in this case, it caused a burning sensation on the skin.

When the researchers asked each person to report both the intensity and the unpleasantness of the pain—in other words, how much it physically burned and how much this level of burning bothered them—they came to the surprising finding. “We found that with THC, on average people didn’t report any change in the burn, but the pain bothered them less,” Lee said.

This indicates that marijuana doesn’t function as a pain killer as much as a pain distracter: Objectively, levels of pain remain the same for someone under the influence of THC, but it simply bothers the person less. It’s difficult to draw especially broad conclusions from a study with a sample size of just 12 participants, but the results were still surprising.

Each of the participants was also put in an MRI machine—so the researchers could try to pinpoint which areas of the brain seemed to be involved in THC’s pain relieving processes—and the results backed up the theory. Changes in brain activity due to THC involved areas such as the anterior mid-cingulate cortex, believed to be involved in the emotional aspects of pain, rather than other areas implicated in the direct physical perception of it.

Additionally, the researchers found that THC’s effectiveness in reducing the unpleasantness of pain varied greatly between individuals—another characteristic that sets it apart from typical painkillers. For some participants, it made the capsaicin cream much less bothersome, while for others, it had little effect.

The MRI scans supported this observation, too: Those more affected by the THC demonstrated more brain activity connecting their right amydala and a part of the cortex known as the primary sensorimotor area. The researchers say that this finding could perhaps be used as a diagnostic tool, indicating for which patients THC could be most effective as a pain treatment medicine.

After decades of uncertainty, a new study confirms that both polar ice sheets are melting. Image via Ian Joughlin

Over the past few years, one of the most difficult pieces of evidence to fit into the climate change puzzle has been ice melt. Although the amount of ice covering the Arctic has clearly decreased over time, climate change skeptics have pointed to inconsistent findings on Antarctic ice as proof that the atmosphere isn’t really warming.

Today, with the United Nation’s COP 18 climate negotiations underway in Qatar, a comprehensive study published in Science provides a timely confirmation: The ice sheets covering both Greenland and Antarctica are steadily shrinking, losing roughly 344 billion tons per year in total. Using data from 10 different satellite missions, an international team of 47 scientists has generated a new estimate for ice loss that is more than twice as accurate as previous models, and indicates that the last 20 years of melting at the poles has caused sea level to increase by 11.1 millimeters worldwide since 1992.

“Our new estimates of ice sheet losses are the most reliable to date, and they do provide the clearest evidence yet of polar ice sheet losses,” Andrew Shepherd of the University of Leeds, the study’s lead author, said in a press call. “They also end 20 years of uncertainty concerning changes in the mass of the Antarctic and Greenland ice sheets, and they’re intended to become the benchmark dataset for climate scientists to use from now on.”

Melting glacial ice drains through vertical crevasses called moulins, eventually flowing beneath the ice sheet and reaching the ocean. Image via Ian Joughlin

Those 20 years of uncertainty are the result of several difficulties inherent in measuring ice melt. Relative to the overall size of the ice sheets, the potential change scientists have been attempting to measure is tiny—on the order of 1 part in 100,000—so sampling errors have led to numbers that vary widely. Gains and losses of ice can also vary from year to year, and from place to place within the same ice sheet. Additionally, the natural seasonal cycle in which sheets add ice during the winter and shed it during the summer makes it even harder to pinpoint the net change over time.

To resolve these difficulties, the researchers assimilated data produced using several different satellite techniques. In one, a satellite in orbit is used to point a laser at glacial ice; the time it takes for the light to bounce back to the satellite indicates the glacier’s precise height, allowing scientists to determine its volume. As part of another technique, a pair of satellites passing over the poles measure the subtle tug of gravity caused by the ice sheets’ mass, and chart the change in the force of this gravity over time.

This data was combined with information collected by regional field surveys and existing climate models that estimate changes in ice cover based on measured precipitation rates and temperature. Despite the variation between years and particular locations, the researchers found that the satellite data fit well with the models’ predictions, and confirmed the hypothesis that as a whole, both ice caps are melting.

The new estimates are that, from 2005 to 2010, Greenland lost roughly 263 billion tons of ice per year, while Antarctica lost 81 billion tons annually. Each year, all this melting causes about 0.6 millimeters of sea level rise. Most alarmingly, both of these ice sheets are melting three times faster than they were in the 1990s.

The melting of the ice caps is troubling as an indicator of the planet’s overall warming, but it could also be problematic in itself, in ways that are both obvious and counterintuitive. For one, sea level rise is a direct threat to both human populations and natural ecosystems along the coasts, as starkly illustrated by Hurricane Sandy and other storms over the past year.

Less obvious is that, according to a study published last month, melting Greenlandic ice could change the salinity of the North Atlantic enough to alter weather patterns in North America and affect aquatic wildlife. By reducing water circulation overall, it could even lead to less carbon dioxide being absorbed into the oceans from the atmosphere, ultimately serving as a positive feedback loop that accelerates climate change.

Of course, finding evidence that the climate is changing has been far easier than coming to international agreements about how to stop it. Scientists can refute the arguments used by climate change skeptics, but if the COP 18 negotiations accomplish as little as most expect, all the data in the world won’t change the fact that it’s uncontrollably warming.

An artist’s rendering of CFBDSIR2149, as viewed through an infrared filter. Image via L. Calçada, P. Delorme, Nick Risinger, R. Saito, European Southern Observatory/VVV Consortium

The astronomy world is abuzz over the discovery of an exoplanet in a nearly unprecedented situation: It’s the first observed to be hurtling through space on its own, rather than orbiting a star. The find, reported by researchers from the University of Montreal in a paper published Wednesday in the journal Astronomy and Astrophysics, is roughly 100 light-years away and has been labelled CFBDSIR2149.

“Although theorists had established the existence of this type of very cold and young planet, one had never been observed until today,” Étienne Artigau, an astrophysicist at the University of Montreal, said in a statement. Over the past decade, astronomers have spotted several candidate objects that could potentially qualify as drifting planets, but the line between what is called a “planet” and what is called a “star” is fuzzy, especially when observing from a distance. Through a telescope, it’s hard to differentiate whether a small solitary object is a “homeless” planet (as the researchers have termed this one) or a brown dwarf, the smallest type of star. The researchers concluded that this is a planet, and one that is 50 to 120 million years old and about 400 degrees Celsius in temperature.

Because this object appears to be traveling through space along with a diffuse group of roughly 30 associated stars called the AB Doradus Moving Group (but does not orbit any of them), the astronomers were able to work out several more pieces of information about it, such as its age, mass and temperature, based on the assumption that the planet likely shares an origin with the rest of the stars in the group. Objects must be less than 13 times the mass of Jupiter to be considered a planet, rather than a brown dwarf, and this object appears to have a mass between four and seven times that of Jupiter, making it an unqualified, starless planet, the first of its kind.

Scientists have speculated that this type of object could result from a normal planet being flung out of its solar system, or could form alone in its present state. Theories of planet and star formation imply that there might be an extremely high number of such solitary planets—they might be as common as normal stars.

For astronomers, the problem is seeing them. Unlike stars, these objects don’t emit a large amount of light. This planet was detected using data from the Canada-France-Hawaii Telescope, located on the summit of Mauna Kea in Hawaii, with further details worked out using the ESO’s Very Large Telescope in northern Chile. Using infrared images from both telescopes, the research team was able to pick out the slight amount of light emanating from the planet, even though it is clearly outshined by the brighter stars:

The pale blue dot at the exact center of this infrared telescope image is the newly discovered “homeless” planet. Image via P. Delorme, European Southern Observatory

This image might seem extremely faint, but compared to most exoplanets—which are typically spotted only when they cross in front of the star they orbit or known from how they make their star wobble—astronomers can see this planet much more clearly because there is no competing starlight in the immediate vicinity. “Looking for planets around their stars is akin to studying a firefly sitting one centimeter away from a distant, powerful car headlight,” Philippe Delorme, the lead author of the study, said in a statement. “This nearby free-floating object offered the opportunity to study the firefly in detail without the dazzling lights of the car messing everything up.”

The researchers say that free-floating planets like this one are scientifically significant beyond their apparent uniqueness. “These objects are important, as they can either help us understand more about how planets may be ejected from planetary systems, or how very light objects can arise from the star formation process,” Delorme said. “If this little object is a planet that has been ejected from its native system, it conjures up the striking image of orphaned worlds, drifting in the emptiness of space.”

Research shows that the FDA’s proposed graphic warning labels would be more effective than the current text-only ones. Image via FDA.

More than 40 countries around the world force cigarette companies to print graphic images of things like decaying teeth, open-heart surgeries and cancer patients on their packs, in an effort to discourage smoking by directly linking cigarettes with their most gruesome effects. The United States, however, is not one of these countries: The U.S. Food and Drug Administration unveiled graphic designs in November 2010, but repeated lawsuits by the tobacco industry have delayed implementation of the new warnings.

If and when the labels do hit, the images could go a long way towards continuing the decline in smoking rates across the country. That’s because, as new research demonstrates, seeing these images every time a person reaches for a pack is a more effective deterrent than a text-only warning. The research also indicates that the graphic warnings are especially powerful in discouraging low-health literacy populations from smoking—the one group in which smoking rates have remained stubbornly high over the past few decades.

The study, published yesterday in the American Journal of Preventive Medicine [PDF], was conducted by James Thrasher of the University of South Carolina and colleagues. A control group of 207 smokers saw text-only warning labels, while 774 smokers evaluated nine different graphic labels, both images proposed by the FDA and a selection of others currently used in foreign countries.

The smokers were asked to judge each label on a scale of one to ten for credibility, relevance and effectiveness. The results were unequivocal: The text-only warnings’ average ratings were mostly in the fives and sixes, while simpler text messages combined with striking graphics scored in the sevens and eights across the board.

These differences were especially large for the group the researchers called low-health literacy smokers–people with less education who are less likely to be knowledgeable about the risks of smoking. This group gave much higher ratings for credibility, in particular, to the labels that showed them the health problems that arise from smoking, rather than text labels that merely told them. “The present study provided the first direct test of the hypothesis that pictorial health warning labels work better than text-only labels among people with low health literacy,” Thrasher said in a statement.

The study also found that graphic types of labels (left) were more effective than those depicting human suffering (middle) or those that were merely symbolic (right). Image via American Journal of Preventive Medicine

Among the labels with images, the study compared three different types: graphic (those that directly showed body parts damaged by smoking), human suffering (those that showed someone in a hospital bed, for example) and symbolic (more abstract images, such as a gravestone). Perhaps unsurprisingly, the first category was consistently rated as the most effective in discouraging smoking. It seems nothing so powerfully scares someone away from taking another puff than a picture of what their teeth, lungs or throat will look like after a lifetime of doing so.

Thrasher feels that these types of findings should be taken into account when agencies such as the FDA design cigarette warning labels, to be sure they reach all demographics. “The FDA should consider implementing warning labels with more graphic imagery in order to maximize the impact of warnings across different populations of adult smokers, including more disadvantaged smokers,” Thrasher said.

An artist’s rendering of the theorized Earth-like planet, potentially capable of containing liquid water. Image via University of Hertfordshire/J. Pinfield

The latest in a long string of recent exoplanet discoveries could be the most exciting one yet: A planet called HD 40307g, roughly 44 light years away, appears to be the most likely candidate to harbor life of any exoplanet we’ve discovered to date. Larger than Earth, but smaller than a gas giant, the planet seems to be in the “goldilocks” zone of its star system, the region with the right balance of heat and cold to potentially allow for liquid water.

To be clear, the discovery (described in a paper published yesterday in the journal Astronomy and Astrophysics), like nearly all other exoplanet discoveries, is indirect and theoretical. Rather than observing the planet with a telescope, a team of astronomers led by Mikko Tuomi of the UK’s University of Hertfordshire analyzed existing public data produced by the European Southern Observatory and realized it contained hints of something rather interesting. While scientists had previously looked at the star HD 40307 and found it was orbited by three planets, these astronomers used more sophisticated detection techniques to discover that it’s actually orbited by at least six.

One of these, HD 40307g, is the one that seems capable of potentially harboring life (exoplanets are named for their host star, along with lowercase letters starting with b and moving outwards—although some have argued that we really ought to be giving these distant planets more interesting names). The planet is roughly 7 times the mass of Earth, so is categorized as a Super-Earth, and orbits its star at a distance of 55.8 million miles, much closer than our distance from the sun, roughly 93 million miles.

This increased proximity is actually a good thing, though, because HD 40307 is slightly dimmer and colder than the sun, so the planet’s closer orbit lands it smack in the middle of its system’s habitable “goldilocks” zone, where liquid water can exist on a planet’s surface. This distance also means that the planet likely rotates on its axis, rather than having one side always facing inward, allowing for a day-and-night cycle that some scientists say increases the chance of life evolving. Additionally, it orbits its star once every 197.8 days, potentially even allowing for a seasonal climate like we have on Earth.

Image via Space.com

The astronomers relied upon the subtle effects of the planet’s gravity on its star to indirectly calculate its existence. ”The gravity of the star causes the planet to orbit it, but the planet has gravity too. As it circles the star, the star makes a littler circle too,” Phil Plait writes at Discovery‘s Bad Astronomy blog. “As the star makes its circle, half the time it’s approaching us and half the time it’s receding. This means its light is Doppler shifted, the same effect that makes a motorcycle engine drop in pitch as it passes you.” By precisely measuring a star’s Doppler shift, astronomers are able to indirectly tell if it is orbited by planets.

While this type of technique had previously been applied to HD 40307, Tuomi’s team used new methods of digitally canceling out visual background noise (such as the star’s solar flares and sunspots) to allow for the more sensitive detection of exoplanets that rotated out a little bit further. This led them to detect the presence of three more exoplanets in the system.

This indirect method allows us to determine the mass, distance and orbital period of each planet, but that’s about it. We don’t know the diameter of the planet, so it could have an Earth-like density with a much larger size, or it could have an Earth-like diameter with a super high density. The system is close enough to us, some speculate, that next generation telescopes might be able to see it directly.

Scientists have long sought to find planets in their systems’ “goldilocks zones” because of the longstanding belief that liquid water is necessary (but not sufficient) for the evolution of life as we know it. So far, most planets that we had found in habitable zones turned out to be gas giants, or have other characteristics that seemed to disqualify the presence of life. So even if HD 40307g turns out to not harbor life, the fact that we’ve finally found a seemingly habitable planet in such an area is a clue that Earth-like planets might not be as terribly rare as some have assumed.