Many of the studies involving smart phone use are critical of them. The latest study involves one hundred thousand young people who received their first smartphone at age twelve or younger. By the time they were between eighteen and twenty-four, these same people reported a wide range of emotional well-being problems, such as disrupted sleep, aggression, detachment from reality and low self-worth. Authors suggest the developing mind of younger smartphone users are more vulnerable to the digital age. The study, published in the Journal of Human Development and Capabilities, says current evidence does not yet prove a direct cause between early smartphone use and later well-being issues. But it argues the potential harm is too great to ignore.