Thank you for sharing your questions about the potential link between mental health disorders and Internet addiction. I hope these answers help increase your understanding of how excessive Internet use may be harmful to one’s health.

@myr00dle asks: Is it true that a leading cause of ADHD is excessive Internet use?

Studies have suggested a link between excessive Internet use and attention deficit and hyperactivity disorder. For example, a 2004 South Korean study of 535 elementary students found that 33 percent of those with attention deficit disorder were “addicted” to the Internet. Similarly, a 2008 Taiwanese study of 216 college students reported that 32 percent of “Internet addicts” had attention deficit disorder compared with only 8 percent of non-addicts. However, while such studies show a strong correlation, they do not establish cause-and-effect. It is possible that kids who are already attention-deficient are more likely to gravitate to the Internet. Still, it seems intuitive that it would be hard to go from spending 56 seconds, on average, on every web page we visit to reading Dostoevsky.

James asks: Is there any evidence that Internet addiction is dopaminergic? On a related note, which psychological disorders are associated with increased Internet addition?

Based on the studies conducted so far, depression appears to be the most common condition occurring in individuals with problematic Internet use. The studies, however, don’t tell us if the person sought to “self-medicate” a depression by going online or if the depression resulted from excessive time spent using the Internet, perhaps at the expense of more rewarding real-life interactions.

Problematic Internet use and problematic online video game use have been called “behavioral addictions.” The neurotransmitter dopamine has long been implicated in addiction to substances and some preliminary small studies suggest a link between a dysfunctional dopamine system and problematic Internet or online video game use as well. In one study, “Internet addicts” were found to have altered glucose metabolism in brain regions that include major dopamine projections. Another study linked a variant of the dopamine D2 receptor gene with excessive online video game use. A third study used positron emission tomography (PET) to show lower levels of D2 dopamine receptors in parts of the brain of individuals with “Internet addiction.” Finally, a recent study showed lower levels of the dopamine transporter in parts of the brain of problematic Internet users.

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