It does not cause physical dependence, but neither does marijuana. Stimulation Like no other mass medium TV can provide stimulating experiences, without us having to do much for it. By combining moving pictures with sound it engages multiple senses to draw us into a different world. Our brain gradually adjusts to this stimulation by filtering out more data, by reducing attention. Children who grow up watching several hours of TV a day will have problems concentrating for any length of time, especially when there is little stimulation as when they are listening to a teacher standing in front of a blackboard.
TV can become quite harmful when it is abused as a babysitter.
Entertainment TV is uniquely suited to entertainment and it has a builtin tendency to turn all forms of content into entertainment, even when it attempts to be educational. There is no borderline any more between commercials and entertainment. Even news programs have had to become more entertaining, at the expense of information. When TV tries to be educational it tends to swerve towards subjects that lend themselves to audiovisual impact and neglects everything else. It's like a teacher who can't see his class and whose payscale is based on his popularity.