Louis Theroux: By Reason of Insanity, review: The affable Englishman routine is wearing a bit thin

Episode 2: Even a man as perceptive as Theroux struggles to scratch the surface

Louis Theroux: By Reason of Insanity, Twin Valley Behavioral Healthcare Hospital, Columbus, Ohio

In Joe Penhall’s 2000 play Blue/Orange, which explored mental health treatment in the UK, one doctor explains to another (Billy Nighy to Andrew Lincoln, no less) that ‘hey, some people are just like that’.

You can throw all the labels you like at it – delusional, borderline personality disorder, anti-social behaviour – but some people are just like that. In the second part of Louis Theroux’s By Reason Of Insanity the affable Englishman meets the patients of Ohio’s State Psychiatry Hospitals whose personalities were so enmeshed with their illnesses that it made them near impossible to diagnose, let alone treat. Where does the personality end and the illness begin?

In the cases of Charles and Dean their diagnoses provided relief. For Charles this meant avoiding trial for four counts of aggravated robbery (and a subsequent hefty spell in prison); for Dean an acceptance that he might have been in his right mind when he committed his crime would make him "a monster". Dean, when aged 18, had sexually assaulted his own mother. "I just think he wanted to do it, so he did it" she explained. Both these men were eager to believe it isn’t simply a case that they are "just like that".

Louis Theroux: By Reason of Insanity, Twin Valley Behavioral Healthcare Hospital, Columbus, Ohio

As for sad-eyed old Louis, we know the drill by now. Our narrator enters a remarkable setting and strolls about harmlessly, teasing information out of people by playing the humble, blank canvas. Theroux’s talent is well documented, his uber-low status disarming his interviewees to the extent that they feel unguarded enough to spill the beans. Inside the wards he chatted to patients, some of whom had committed the grisliest of acts, as if saying hello to a next door neighbour. There’s not an ounce of superiority or judgement in Theroux’s bearing and you can see his subjects visibly soften as he allows them to believe, as he always does, that they have the upper hand.

Louis is at his best when unmasking people (the Westboro Baptist Church, Jimmy Savile) – tying liars and fakers in knots, always giving them enough rope. We had a flavour of that with Ohio’s own RP McMurphy, Charles, who, at least one doctor believed, was "playing the system"’. Louis got under his skin. "I’m not saying I’m malingering, I’m not saying I’m not malingering," he said. "I’m choosing my words carefully". As was Louis.

However, the act is wearing a little thin (the reason perhaps why he now does all his work in America) and his recent subjects have been so weighty that even a man as perceptive as Theroux struggles to scratch the surface of them. Here, as with his recent shows on paedophiles and children with severe autism, it occasionally becomes an episode of "intelligent, sensitive man feels a bit sad about difficult things". While you’re left with admiration for those who treat and care for the mentally ill, By Reason Of Insanity ended with a bit of a resigned shrug. What can be done?