Psychosis occurs for many reasons. Schizophrenia, bipolar disorder being the most common.
When my daughter suffered a Stroke at 13, a close school friend of hers was in the room next door suffering psychosis purely due to Thyroid issue.
Psychosis due to alcohol is usually short lived and only occurs in those who are alcohol dependent or withdrawing from heavy alcohol abuse.
That's right. People experiencing psychosis react to internal stimuli such as hearing voices or having paranoid thoughts they can't shake. Typically it's related to schizophrenia or extreme bi polar disorder but can also manifest due to some sort of illness like brain tumor or diabetic episode, etc.
A psychologist told me that it is typically lack of sleep for long periods and/or dehydration that causes a psychotic episode in people other than schizophrenics. So they may be manic and unable to sleep or care for themselves and their mind sort of splits.
We see this in some famous people sometimes or people under extreme pressure like Brittany Spears, Amanda Bynes, that guy who went crazy -Jason Russell- and took all his clothes off in San Diego.
Psychosis is the most classic form of mental illness when it is defined.
Besides psychosis, mental illness is separated into two other main categories- neurotic disorders like depression, anxiety, OCD, and character disorders like narcissistic, borderline, histrionic, anti-social, per what a psychologist told me.
However, the judge stated that AC showed no signs of mental illness. He would've been tested as part of his presentencing report and apparently nothing was found, except some cold callous traits which some have mentioned would not lead to a diagnosis of anti-social personality disorder due to his age.
But that rules out any neurosis or psychosis.
This is a cold human being with full control of himself and his choices.