The movies have always been glib in how they depict mental illness. And there are a few minutes at the beginning of “Paper Spiders” where you can wonder if we aren’t about to be treated to more of the same.

A clingy, widowed Mom (Lili Taylor) makes inappropriate remarks and superstitious dismissals of the school to her half-smothered daughter (Stefania LaVie Owen) as the kid checks out a prospective college. It’s really all about Mom.

“Why did I push you to make straight As? I just pushed you right out the door.”

But any cutesie “Terms of Endearment” delusions go right out the door, and in a hurry, as mother Dawn’s delusions become manifest, manic and overwhelming, threatening to derail daughter Melanie’s future and turn her present into a living hell.

“Paper Spiders” is a bluntly-realistic portrayal of how a lone teenager might cope with or compensate for such a situation, and where she can and frankly cannot expect to find help when her only parent goes crazy.

Driven by a sober, case-study-real and wild-eyed performance by Taylor — from “Mystic Pizza” to the new “Perry Mason” one of the finest actresses of her generation — and anchored in the overwhelmed kid Stephanie LaVie Owen (“I’m Dying Up Here,” “Krampus”) shows us, this sad, anxiety-inducing drama about what results from Mom’s mania is a veritable tutorial on “Mental Illness Hits Home.”

Melanie is a smart kid — class salutatorian at Erie Canal High. She’s always written-off Mom’s quirks as “neurotic.” But she’s just reached an age where she can see more and process it with growing alarm.

It “starts” with the new neighbor Mom instantly gets into a feud with. She becomes convinced “he” is watching them, throwing rocks, sneaking around and into their house and worse. Melanie takes all of this seriously, up to a point.

Mom calling the cops is a tipping point. Hiring a private detective (Max Casella) is the next “logical” step.

Seeing Dawn at work with an aging, long-suffering lawyer (David Rasche), we wonder how long it’ll be before she snaps there and that job is gone.

Melanie seeks help close-at-hand, from the school mental health counselor (Michael Cyril Creighton).

“I’m here because of my Mom” earns a “Me, too” from him. He veers between flippant and uncaring to consulting a textbook for a “diagnosis” and then dithering on beyond his pay grade.

And then there’s the obnoxious, hunky new rich kid at school (Ian Nelson), a “playa” who zeroes in on Melanie. He’s persistent, drives a BMW convertible and always has a flask or water bottle spiked with vodka. Considering the other “issues” in her life, Melanie starts to give in a little.

That too, by the way, is textbook behavior.

Director and co-writer Inon Shampanier (“Beautiful and Twisted,” “The Millionaire Tour”) makes us anxious for Melanie, and LaVie Owen makes us fear for this sweet kid unable to figure out how to help her mother and trapping herself with a feckless boyfriend who will either lean on her for sobriety or drag her into the bottle, bong or brownie with her.

Every movie hits every viewer a little differently, and this one pulled me right in. This is exactly the way such situations often play out — tirades, paranoia, threats of involuntary commitment, a child forced to make adult decisions.

Shampanier keeps the anxiety level high all the way to the closing credits, offering a little hope but taking incredible care to highlight the “no easy choices” and “no end in sight” difficulties facing Melanie, and the lesson that Mom “didn’t choose to be mentally ill, any more than somebody chooses to get cancer.”

This is a scenario with no villains — not Mom, not the neighbors Mom suspects, not the potentially-predatory PI she hires, not even the half-clueless-but-trying school counselor.

And as “Paper Spiders” suggests, it’s not just the terror that witnessing this sort of breakdown creates, it’s the relentless, insidious nature of the illness and the utterly deflating realization that doing this or doing that is awful, and taking no action is worse.

The cast and filmmakers have made a very good movie about a very tough subject. and somehow have managed to never cop out once by showing us easy answers.

MPA Rating: TV-MA, teen drinking and sex, profanity

Cast: Stefania LaVie Owen, Lili Taylor, Peyton List, David Rasche, Ian Nelson and Max Casella

Credits: Directed by Inon Shampanier, script by Inon Shampanier, Natalie Shampanier. An Entertainment Squad release.

Running time: 1:50