Really? When I was a kid it was synonymous with after school special type episodes. The ones in which Alexs' friend dies in a car crash or we learn Theo is dyslexic or Dorothy has chronic fatigue syndrome or the Bowers new neighbours turn out to be a single mom who kidnapped her kid after losing the custody hearing, or a teen character tries drinking/drugs or is worried about the environment or arms race or homelessness.
Those too ...