How does one tell if a teenager really has depression or is pretending to (to get out of chores, schoolwork, etc)?

Teen depression: Depression in teenagers may look like a bad child instead of a sad child. Teens may begin smoking, drinking alcohol or using drugs. They may stop doing homework and academics may take a nose dive. Arguments with parents and siblings may increase. They may be irritable. A previously compliant teen may now become a defiant one. Con't.