Excessive internet use may cause parts of teenagers' brains to waste away, a study reveals. Scientists discovered signs of atrophy of grey matter in the brains of heavy internet users that grew worse over time. This could affect their concentration and memory, as well as their ability to make decisions and set goals. It could also reduce their inhibitions and lead to ‘inappropriate' behaviour. Researchers took MRI brain scans from 18 university students, aged 19, who spent eight to 13 hours a day playing games online, six days a week. The researchers compared them with a control group of 18 students who spent less than two hours a day on the internet. One set of MRI images focused on grey matter at the brain's wrinkled surface, or cortex, where the processing of memory, emotions, speech, sight, hearing and motor control occurs. Comparing grey matter between the two groups revealed atrophy within several small regions of all the online addicts' brains. The scans showed that the longer their internet addiction continued, the ‘more serious' the damage was. The study, published in the PLoS ONE journal, was carried out by neuroscientists at universities and hospitals in China, where 24 million youths are estimated to be addicted to the internet.