Disorder under construction
What the changes in both white and gray matter indicate are murky, but the research team has some ideas.
The abnormality in white matter in the right parahippocampal gyrus may make it harder for Internet addicts to temporarily store and retrieve information, if a recent study is correct. Meanwhile, the white matter reduction in the left posterior limb could impair decision-making abilities—including those to trump the desire to stay online and return to the real world. The long-term impacts of these physical brain changes are even less certain. Rebecca Goldin, a mathematician at George Mason University and director of research for STATS, says the recent study is a big improvement over similar work published in 2009. In this older study a different research group found changes in gray matter in brain regions of Internet addicts. According to Goldin, however, the study lacked reliable controls.
The sample sizes of both studies were small—fewer than 20 experimental subjects each. Yet Friston says the techniques used to analyze brain tissue density in the new study are extremely strict. "It goes against intuition, but you don't need a large sample size. That the results show anything significant at all is very telling," Friston notes.
In the end all of the researchers interviewed by Scientific American emphasized significance only goes so far in making a case for IAD as a true disorder with discrete effects on the brain. "It's very important that results are confirmed, rather than simply mining data for whatever can be found," Goldin says.
Correction (06/17/11): This story was updated throughout to correct the spelling of Karen von Deneen's last name.