teratoma. a type of germ cell tumor made up of a number of different types of tissue from one or more of the germ cell layers; it is usually found in the ovary or testis and may be either benign or malignant.
That is why obsession with watching TV can cause some dangerous addictions. The other group of effects, which can be caused by watching too much of television, is connected with possible mental disorders or disturbances. The most spread of those are attention deficit disorder and other problems with emotional health.
It is reasonable to think that the more TV you watch, the less time you spend studying, resulting in low test grades. However, it does not seem like these variables will be strongly correlated, since some people do not watch TV but do not spend time studying either.