Intentional or not, Steven Soderbergh’s psychological horror film “Unsane” (Bleecker Street), shot on an iPhone 7, comes across as an homage to Brian DePalma, complete with the casting of Amy Irving (who starred in DePalma’s “Carrie” and “The Fury”). Think about “Dressed to Kill”’s commentary on psychiatry. The way “Blow Out” manipulated perceptions and versions of the truth. The obsessive behavior in, you guessed it, “Obsession.”

There are spoilers ahead. Consider yourself warned. Directionless young woman Sawyer (Claire Foy) has attempted to find herself through various types of education and employment. Before accepting a position which put her in a cubicle in a bank, she worked in hospice. It was there that she met David (Joshua Leonard), the son of an Alzheimer’s patient, and her life was forever changed. For the worse.

Struggling with ways to cope with David’s obsessive stalking, Sawyer finally speaks with a therapist. Through a series of miscommunications and unfortunate actions (always read every form before signing it), Sawyer unknowingly checks herself into a psychiatric treatment facility. Unnerved by the situation, including unpleasant interactions with fellow patients Violet (Juno Temple) and Jacob (Raúl Castillo of “Looking” fame), as well as staff members, Sawyer finds her stay extended because she is considered a danger to herself and others.

Matters only get worse when Sawyer is convinced that one of the nursing staff is David masquerading as someone named George. Thankfully, Sawyer is able to connect with one patient, Nate (Jay Pharoah), who becomes a source of comfort and aid to her.

Sawyer is able to contact her mother Angela (Irving), using Nate’s contraband mobile phone. Angela arrives in full Shirley-MacLaine-in-Terms-of-Endearment mode. Unfortunately, Sawyer is right about David/George, and that doesn’t bode well for Nate, Angela and others.

For the most part, “Unsane” does a good job of keeping us guessing on the “is she or isn’t she?” scale. The movie belongs to Foy from start to finish (you have to see the final scene to believe it), and she is very convincing throughout. Soderbergh regular Matt Damon steals his scenes as an uncredited police detective who counsels Sawyer about stalker preparedness.

Amidst all the, shall we say, insanity, “Unsane” also manages to lash out at the current state of mental health care, the insidious practices of the health insurance industry and the inability of some police forces to protect victims of stalking. Rating: B