So you know how there's two kinds of nuclear reactions when you shove a lot of nuclei into one location: Fission, where they explode, and fusion, where they get all screwed up. Either way, lots of power in there. It's a synthetic hothouse and the things can't help but interact.
And you know how the nuclear family as a unit was only invented like two hundred years ago, and our "classic" nuclear family in America is really just a dividend from the interstate highway system, isolating these mother/father/children units from each other and shipping the old folks off to sad Hoarders episodes or even sadder old folks' homes: A synthetic hothouse, where the things can't help but react.
The rise of the poltergeist coincides with the invention of the nuclear family. So do eating disorders. We've already talked a lot about the psychic energy bouncing around teenage girls, and why it's such a big deal: Because teen girl sexuality is the most important commodity in the entire universe, and must be controlled. Put that into a reactor like the synthetic nuclear family, and you get this show: Every man is a predator, and every girl knows for a fact that there is something horrible and dirty inside her. Everybody is unimaginably alone, because everybody carries this secret, and since we don't talk about it, we have no idea that everybody on earth feels this way.
Spencer's always carried the football on this one, which is why I'm bringing it up at the very beginning because of what she's about to say -- and because this episode, even for this show, never stops staring right at this idea -- but consider each of the Liars' families in nuclear terms: Aria's family is in total fission, and she's looking for a teacher who'll sleep with his students. Hanna's family is the definition of fission, and she's doing okay considering her mom is just as much of a child as she is. Emily's mom is showing the pressure of being locked up in a house with her daughter's sexuality, while her dad gets to pat her on the head and then run back into war.
Or consider the Cavanaughs, in their Grey Gardens reactor: Jenna, who's willing to do everything to trap her brother in there with her, and Toby who is becoming a ghost himself.
In every case you see a major truth happening, which is that our family psychodramas link us back to antiquity, but only circumstantially: This fusion's one good effect is that it forces the archetypes out much faster and culturally we have to deal with them faster and better. We don't have time to make up fairytales and sand them down to truth over generations, because we're looking it in the face all the time, so we have TV shows and cultural phenomena and memes instead. We're crazier, but also healthier, if you see what I'm saying, because we see it happening and have to account for it in every transaction: Freud, like astrology, is completely invalid but always correct.