The Kubey chapter goes over the definition of addiction. Kubey speculates that addiction may be a form of operant conditioning. TV tends to relax people quickly while they are watching it. In fact, drugs that act quickly tend to be more addictive than drugs that act more slowly. Negative side effects.
TV is reported to be one of the most relaxing of the activities they looked at.
Overall, people who are watching TV are not very challenged, they don't seem to concentrate well and they are not activated. Nor do people watching TV seem to be in a good mood. People watching TV do seem to relax, but they are more relaxed during and after other activities. Analogy to drugs.