A certain degree of loneliness in adolescents is quite normal, and is associated with the adolescent's tendency to lethargy, which is also a characteristic of this stage.
The adolescent's feeling of loneliness may be attributed to not being understood and not being a part of the adult world. Adults' recourse to criticism and continuous and persistent instructions increases their sensitivity and failure to express themselves appropriately because of lack of proper life skills. Moreover, the adolescent's quest for independence as a way to find an identity of his own would create feelings of loneliness.