MTO EXCLUSIVE: Neil From YOUNG AND THE RESTLESS .. . Tried To COMMIT SUICIDE . . . Police Put Him In A MENTAL HOSPITAL!!

Actor Kristoff St. John from the CBS show Young & The Restless was taken into custody - after police fear he tried to commit suicide. Here's what TMZ is reporting:

Law enforcement sources tell TMZ ... Kristoff's ex-wife, Mia, called cops Thursday evening and told them Kristoff had been sending her photos showing the soap star holding a gun to his head.

When cops arrived, they confiscated two guns and placed Kristoff under a 72-hour hold for mental evaluation. Sources close to Kristoff tell us the two-year anniversary of his son Julian's suicide is fast approaching - November 23 - and that had him very, very upset.

Pics of his GF and his daughter: