By Dr. Brian McDonough, Medical Editor

PHILADELPHIA (CBS) – We all know about teenagers who always seem to be playing computer games and there are occasional reports of teens who are supposed to be addicted. Now a new study finds teenagers who are seemingly addicted to the Internet may have abnormal white matter.

White matter is the insulation that surrounds the wiring between neurons. It’s not clear if this difference could cause Internet addiction or actually may be a result of it.

The differences in white matter in the subjects described as Internet addicts is also seen in people with obsessive compulsive disorder and alcohol or drug addiction.

In performing the study, the researchers gave MRI brain scans to 17 adolescents who appeared to suffer from internet addiction. Those who were thought to be addicted felt restless, moody, depressed or irritable when they tried to cut down.