Well it really depends on the content being viewed because if adolescents watch educational shows than the effect can make them smart or smarter than they already were, or if they're are watching too much t.v. that's pulling them away from the real world or just anything inappropriate, this can have bad effects on them since too much of anything is bad for you, even drinking too much water can kill you, so too much t.v. can distract a teen from real world scenarios and situations that can help the teen out, and watching ''adult content'' for a teen would make it addictive and make the teen not act his or her own age.
