Dr. Jeffrey Lieberman — formerly the president of the American Psychiatric Association — stopped by “TMZ Live,” sharing some disturbing insight into the multiple rehab facilities … which ultimately failed Rob and Michele Reiner‘s son Nick.

Before his parents’ tragic murders, Nick was in and out of rehab at least 18 times. While Nick struggled with substance abuse, Dr. Lieberman suggested the care he received was palliative at best … and after-care at rehabilitation programs is generally inadequate, resulting in a revolving-door repetition of treatment and release.

Lieberman said, “[Rehab centers] don’t necessarily provide mental healthcare for a primary diagnosis such as schizophrenia, which may have been the reason that impelled Nick to use illegal medications, which he became addicted to.”

Some have pointed out Nick had been displaying warning signs when his medications were altered in a way that left him unstable. While Lieberman says it should fall on doctors to spot dangerous behavior and prescribe in patient care when necessary, he admitted the law ties their hands.

“The rules for civil commitment, or treatment of a patient over objection, or hospitalizing them over objection are so stringent that a person has to literally commit a crime before they can be forcibly admitted to the hospital or required to take medication,” he said.

This even applies in Nick’s case, where he was allegedly using cocaine, which Lieberman said is like “throwing gas on a fire” for schizophrenics.

Lieberman lamented, “What we have here is a result of the inattention to this problem, which is good mental healthcare … We’re introducing to the population ticking time bombs.”