Nick Reiner was diagnosed with schizophrenia, and in the weeks leading up to the murder of his parents, Rob and Michele Reiner, the meds he was taking made him “erratic and dangerous” … TMZ has learned.

Two sources with direct knowledge tell TMZ … Nick was under the care of a psychiatrist for mental illness. We’re told in the month before the murders, Nick’s behavior had gotten “alarming.”

He had recently received care at a Los Angeles-based rehab facility that specializes in mental illness and substance abuse. We’re told the facility charges $70,000 a month … and lots of rich, powerful parents send their troubled kids there.

Before ya guzzle down a bunch of holiday treats over the next few days, here’s Cristiano Ronaldo reminding folks what’s possible with a ton of discipline and living in the gym.

The 40-year-old international soccer star went to social media to show off his Greek god-like bod on Friday … telling his 105 MILLION X followers he just hopped out the sauna — and, lucky for us, providing visual proof.

The Al Nassr striker rocked nothing but black briefs and slides for the photo op … making sure his chiseled abs and veiny legs were on full display.

The “Ghost Adventures” episode featuring Weezer bassist Scott Shriner’s ex-wife, Jillian, is about to air … and TMZ’s got the chilling first look, giving a pretty unsettling peek into her headspace before that wild run-in with cops earlier this year.

Have a look — Zak Bagans says things took a seriously dark turn after Jillian gifted him serial killer Samuel Little‘s ashes, along with hand-drawn portraits of his victims that he’d left her in his will after she once wrote a book about him.

Zak says Samuel’s remains were placed inside his Vegas Haunted Museum, alongside Charles Manson’s, and it wasn’t long before strange activity started popping off … triggering a pretty intense reaction from Jillian.

Jillian says those ashes were literally in her home, and every time she walked into the room, she felt herself folding, sinking deeper into depression.

Remember … production sources told TMZ Jillian filmed the episode in November last year … and just months later, in April, she allegedly fired a gun at officers searching for a suspect near her Los Angeles home in an unrelated incident.

Jillian was arrested on suspicion of attempted murder of a peace officer, but prosecutors later downgraded the charges to assault and negligent discharge of a firearm. She avoided jail time — with a judge granting her diversion due to mental health issues.

We broke the story that Jillian filed to divorce Scott earlier this month after being married for 20 years.