In addition to short term issues, there are so many long-term consequences of excessive technology use. This is why it's important to set technology boundaries with young children, and to continue explaining, discussing, and modifying technology boundaries in your home with older children.
Digital dementia, deterioration of cognitive abilities, similar to a head injury or psychiatric illness can occur. People who rely on electronic devices often can't remember important everyday details of life.
Brain development can be affected. Heavy digital users are likely to develop the left side of their brains, leaving the right side less used or underdeveloped.
Digital addiction: when a person lives much of their life online, and excessive internet or device use interferes with activities of daily living or social relationships. ( Signs and Symptoms of Internet Addiction )
Sooo....have you had that discussion with your teenagers? How did it go?