There are mentions of a main character being institutionalised. There is a scene of a psychotic breakdown in one episode, but it lasts less than 1 minute.
Two 6yo children are vocal about unwillingness to stay with religious extended family who make them pray against their will; subsequently, both boys are murdered in their sleep.
In the first episode at 30:15 Jeremy Bamber is given some bad news by a police officer and is asked if he’d like to sit down. He says he’s fine and then starts to sob and vomits.