A new study provides evidence that heavy internet use by the young results in “brain structural alterations” of a kind associated with “impairment of cognitive control.” The study, published this month in PLoS ONE, was conducted in China, where approximately 14 percent of urban youths – some 24 million kids – are believed to suffer from so-called “internet addiction disorder.” Using brain scans, the researchers compared the brains of 18 adolescents who spend around eight to twelve hours a day online (playing games, mainly) with the brains of 18 adolescents who spend less than 2 hours a day online. The heavy Net users exhibited gray-matter “atrophy” as well as other “abnormalities,” and the changes appeared to grow more severe the longer the kids engaged in intensive Net use.

The whole subject of Internet addiction remains controversial among experts, but, according to a Scientific American article on the new research, the study “cuts through much of the debate and hints that excessive time online can physically rewire a brain.” The Scientific American piece translates the key findings into layman’s terms:

One set of [MRI] images focused on gray matter at the brain’s wrinkled surface, or cortex, where processing of speech, memory, motor control, emotion, sensory and other information occurs … The researchers discovered several small regions in online addicts’ brains shrunk, in some cases as much as 10 to 20 percent. The affected regions included the dorsolateral prefrontal cortex, rostral anterior cingulate cortex, supplementary motor area and parts of the cerebellum.

What’s more, the longer the addiction’s duration, the more pronounced the tissue reduction. The study’s authors suggest this shrinkage could lead to negative effects, such as reduced inhibition of inappropriate behavior and diminished goal orientation …

As another crucial part of the new study on Internet addiction, the research team zeroed in on tissue deep in the brain called white matter, which links together its various regions. The scans showed increased white matter density in the right parahippocampal gyrus, a spot also tied to memory formation and retrieval. In another spot called the left posterior limb of the internal capsule, which is linked to cognitive and executive functions, white matter density dropped relative to the rest of the brain. [The researchers suggest that the white matter changes] may make it harder for Internet addicts to temporarily store and retrieve information … [and] could impair decision-making abilities—including those to trump the desire to stay online and return to the real world.

University College London neuroscientist Karl Friston tells Scientific American that while the shrinkage in gray matter is “quite extreme,” it’s “not surprising” when you take into account the plasticity of the adolescent brain: “Our brains grow wildly until our early teens, then we start pruning and toning areas to work more efficiently. So these areas may just be relevant to being a good online gamer, and were optimized for that.” But the study was a rigorous one, and the fact “that the results show anything significant at all is very telling,” Friston says. Further research will be required to confirm the study’s findings and to shed further light on behavioral and cognitive consequences of the changes.