Watching TV often can lead into many problems:-
*Their eyes are surely going to be affected because it is such a stress for eyes watching tv for a long time.
*According to studies,the people who watches tv for a long time die earlier.
* People especially teens who Watch tv for a long time feels more tensed than others.
*It increases dullness in the person.
*It is a type of addiction too....like smoking,alcohol,etc.
*It is a way for many health problems.
Hope it helps and pls mark as the best answer. :-)