What Are The Effects Of Computer To The Health Of The Teenagers?

It depends on the teenager, and their personality. Since computers are well, fun, they can be addictive. Reasons for computer addiction can include:
a) escapism. The teen may have a bad home life or situation, and play online games to escape the real world.
b) niche. The teen may not be "good" at sports, drama, music, or other common occupations for teen kids, but they may find that they are absolutely brilliant at computers and devote time to them.
c) social. Teens may utilize social sites such as MySpace, Facebook, Friendster, or even Eharmony to find friendship, or relationships and become addicted to the fast and easy social interaction.
d) free porn. Teen guys could have this problem.
e) networking. Talented teens may want to get "discovered" via YouTube, and spend their time finding "fans" to help the future music or acting career.
f) homework. Nowadays even 3rd grade teachers assign over-the-top amounts of onine work
g) intellectual. With unlimited knowledge at your fingertips, some of us may simply love the learning experience of the internet.

The only reason that health would be negatively affected would be if the computer caused the teen to have a sedentary lifestyle. But there are worse offenders for that, such as video games and the television.
Health effects include:
a) bad posture from sitting perched at a desk for hours on end
b) insomnia from the "mind crowding" phenomenon
c) stress from a rise in Cortisol levels. Believe it or not, from playing too many games!
d) weight gain from being idle. This is especially true for kids who snack at the computer.
e) poor eyesight. Games like tetris and even Mario can improve hand-eye coordination. But if the screen is too bright, it is bad for the eyes!
f) slow metabolism. Theoretically, an organism should never be totally dormant unless asleep.
sitting still without moving slows the metabolism down, when you should be burning and using calories productively.
g) muscle stiffness. Again, from not moving.
h)loss of vitamin c, and d. Vitamin d comes from the sun. Even though too much sun is bad, fifteen minutes outside can raise vitamin d levels. At the computer? No D is present. Vitamin C comes from food, but becomes effective by excercizing. If there is no exercise and no C, the teen is far more likely to get colds and contagious germs if there is nothing in the immune system to fight them.

I am sixteen...these are my observations. I'm glad you asked this question because I want to go to Medical school. I love this type of thing!