An article from 2017 - haven't found anything more recent on the subject matter yet -
Are Cult Members Insane?
A new study of cult murders in the U.S. suggests that even the deepest and most disturbing convictions are no proof of mental illness—nor, some argue, should they be.
While Holoyda acknowledges that such cases are extremely rare, he concludes that American courts ultimately view cult beliefs—even those that have driven people to murder—as voluntary, no different from religious belief.
[...]
But the last two editions of the
DSM both mention cults. In the fourth edition (issued in 1994), cults are referred to under Paranoid Personality Disorder; in the fifth (issued in 2013), cult involvement was listed as a potential cause of "identity disturbance due to prolonged and intense coercive persuasion." [...]
Holoyda suggests that, under this relatively new definition, cult involvement would serve more as a mitigating factor in a criminal case rather than proof of genuine psychosis. "Someone could testify that a cult member was so beaten and broke by their cult that they simply did whatever they were told to save their lives or to protect themselves," Holoyda says.
Both definitions contain only traces of what is arguably at the heart of the question: the possibility of choice. While First objects to this as a means of distinguishing the sane from the insane, Appelbaum feels it is as close as anyone is likely to get to summing up the difference between a psychiatric disorder and an insane-seeming religious belief. And until the courts or profession of psychiatry are ready to wade into the debate on free will, that may be where the questions should stop.
(more to read at link)