Charlie David-

Not true. 

Sufferers of PTSD can experience episodes of auditory hallucinations and episodes of psychosis as a direct manifestation of PTSD. 

As an aside, someone with Major Depressive Disorder can also experience it is MDD-severe- with psychotic features. 

It's straight out of the clinical mental disorder diagnostic manual, the DSM V. 

Mental disorder does not insinuate dangerous behavior is imminent but uneducated statements about mental illness does not advocate understanding.