“Is it just me or is it getting crazier out there?” Joaquin Phoenix’s proto-Joker Arthur Fleck asks his psychologist in the new Joker movie. The real answer is both. Fleck is a man losing his grip on sanity, but the world “out there” is a powder keg of lawlessness, inequality, corruption, cuts and all-round despair. Joker’s story is set around the early 1980s, but it consciously chimes with our own increasingly crazy present. “These are tough times,” the psychologist acknowledges. She might as well turn and wink to the camera.

It’s no surprise that 2019’s Joker – while set to be a triumph, critically and commercially – has raised concerns over its narrative. An early, leaked version of the script, plus the portrayal of Phoenix’s character as a sad young man losing his grip on sanity (mental health problems, past trauma, failing comedy career, loneliness) has led to the film being aligned with so-called “incel” culture (involuntarily celibate men who are angry and misogynistic).

Early reviewers have expressed concern over what messages the movie might be transmitting, and what actions it might inspire. “In America, there’s a mass shooting or attempted act of violence by a guy like Arthur practically every other week,” wrote Time’s Stephanie Zacharek. Concerned by the part Fleck’s unrequited love for his neighbour (Zazie Beetz) plays in his violent trajectory, she added “he could easily be adopted as the patron saint of incels”. The Telegraph’s Robbie Collin meanwhile wrote: “Make no mistake, this is a film that is going stir up trouble,” admitting he partly felt the film “should be locked in a strongbox then dropped in the ocean and never released”. In a later interview, the Telegraph asked Phoenix if he was “worried that this film might perversely end up inspiring exactly the kind of people it’s about, with potentially tragic results?” Phoenix reportedly got up and walked out.

Joker is not the first comic-book movie to sympathise with the bad guy, but it is the first to do it so one-sidedly. Superhero movies traditionally reassure us that good ultimately triumphs over evil, but Joker heads in the opposite direction. Fleck starts out as a decent but troubled soul. An aspiring standup comedian, he believes his mission is to bring laughter to the world, until life disabuses him of that notion. (Career advice: if you’re a clown entertaining a children’s hospital ward, don’t bring your gun to work.) Snip away the references to Gotham City and the Wayne family, and Joker is barely a comic-book movie at all, more a grim character study of snowballing defeat and humiliation, with no silver lining or caped crusader on the horizon. As the film-makers readily admit, and the casting of Robert DeNiro betrays, Joker follows in the footsteps of Martin Scorsese’s triumphantly bleak 1970s/80s movies Taxi Driver and The King of Comedy. But as critic David Ehrlich wrote in his Joker review: “There’s a fundamental difference between telling a story like this in the form of a dingy, misanthropic art film like Taxi Driver and telling it in the universal language of a superhero movie that’s going to open in multiplexes the world over. In this context, that story can’t help but feel aspirational.”

As much as “doing something Marvel can’t do”, the suggestion is that Joker does something superhero movies shouldn’t do. Perhaps the concern is down to the nature of the Joker himself. It is hard to imagine this kind of story being made with any other comic-book character. The Joker is easily the most recognisable and popular villain in the game, and the most complex. And the most entertaining.

“Every generation gets its own Joker,” says professor Ben Saunders, founder of the comic-book studies minor at the University of Oregon, who has written extensively on superheroes. “Every decade of the past 80 years has had its own version.” He suggests the character’s evolution is the result of a “complex, transmedia feedback loop” between the Joker’s various media portrayals, in comics, TV, animation, film and even video games. “The Joker is actually a series of Jokers – and talented creators are free to play with different elements in producing any new version.” Over his many screen portrayals, the Joker character has been on a steady journey from two-dimensions into three. Cesar Romero’s version in the 1960s Batman TV series captured the character’s trickster sensibility, but he was arguably no deeper than a playing card, reflecting both the tone of the Batman comic books at the time and the half-hour children’s show format, which was all screen superheroes then merited.

Why so serious? Heath Ledger’s iconic portrayal. Photograph: AP

The prankster aspect was still there in Tim Burton’s supposedly “darker” 1989 Batman. Despite coming into being in the era of “graphic novels” such as The Killing Joke and Frank Miller’s The Dark Knight Returns, which explored the characters on deeper levels, Burton’s Batman never pretended to be anything more than a live-action cartoon. In the presence of Michael Keaton’s rather stiff Bruce Wayne, and the absence of a compelling plot, Burton wisely allowed Jack Nicholson to steal the show. With its over-the-top design, retro stylings and Prince soundtrack (plus a fairly uncritical view of mega-capitalism), you could say Burton’s Batman was a very 1980s iteration.

The success of Burton’s Batman set the tone for some woeful sequels, but we would have to wait till Christopher Nolan’s reign for the properly “dark” Dark Knight promised by Miller and Moore, where Heath Ledger’s unforgettable Joker interpretation is often held to be the conclusion of that journey towards three-dimensional characterisation (Jared Leto tried a little too hard to out-Ledger Ledger in Suicide Squad).

How has the role endured? One distinguishing factor that is easily overlooked, points out Travis Langley, a psychology professor who has put many a pop-culture icon including the Joker on the couch, is that Batman has no actual superpowers. “Because Batman is defined by his personality, his enemies have to be as well. No other superhero has such a rich, well-known gallery of enemies, and the Joker is king of them all.” As such, Joker and Batman’s battleground has always been more psychological than physical, which is why Phillips’s serious, straight Joker story fits in so seamlessly. Batman stories are as much about madness and sanity as good and evil; what other superhero world features the local mental asylum as a key location? But Langley hesitates to diagnose the Joker. “His behaviour does not neatly fit into any condition. The Joker is clearly a psychopath. He has no conscience. He has no empathy for anybody. He’s this agent of chaos and you’re just not sure, does he really know what he’s doing or not?”

The Joker’s real superpower is messing with other people’s heads: Batman’s, his henchmen, his adversaries, his lover Harley Quinn, Commissioner Gordon (in Alan Moore’s The Killing Joke), Harvey Dent (in Christopher Nolan’s The Dark Knight), the people of Gotham (in Tim Burton’s Batman), for example). In this light, it seems Joker the movie is being treated as another dastardly scheme to incite madness in the general populace.

So should we be worried about the Joker’s real-world potential for inciting chaos? We have been here many times before, not least with Joker’s inspiration: Taxi Driver, and its part in the attempted assassination of Ronald Reagan in 1982. Shooter John Hinckley Jr was obsessed with the movie. He watched it at least 15 times. He began to model himself on DeNiro’s Travis Bickle, who plots a political assassination and becomes infatuated with a teenage prostitute, played by Jodie Foster. Hinckley dressed like Bickle, collected firearms like him, kept a diary like him, even drank peach brandy like him. And he developed a real-life obsession with Foster, stalking her and writing to her that he had shot Reagan to impress her.

Green initiative... Jared Leto’s slightly overdone iteration. Photograph: Allstar/Warner Bros

At Hinckley’s trial, the defence closed with a screening of Taxi Driver. One of his defence experts stated that Hinckley felt “like he was acting out a movie script”. He was found not guilty of Reagan’s attempted murder on grounds of insanity. It is often a chicken-and-egg situation, or perhaps a transmedia feedback loop. Taxi Driver was itself informed by the attempted assassination of presidential candidate George Wallace, by Arthur Bremer, in 1972. Bremer was another disturbed, lonely young man, obsessed with firearms and pornography, recently dumped by his 16-year-old girlfriend. Taxi Driver’s writer, Paul Schrader, acknowledged Bremer as an inspiration for Bickle, but said that he based the character as much on himself as anyone.

Often it is more stylised, youth-friendly violent movies that strike the “dangerous” chord. A Clockwork Orange, American Psycho, and Natural Born Killers, for example, all of which were implicated in copycat attacks. The latter has a whole Wikipedia page of “copycat crimes”, including the Columbine High School massacre. The media is now hard-wired to make links between movie and real-life violence, even when they’re not there. Bringing the issue closer to home was the 2012 shooting in Aurora, Colorado, which killed 12 people and injured 70. It happened during a midnight screening of The Dark Knight Rises. Early reports claimed witnesses had heard the shooter shouting words to the effect of: “I am the Joker”. He had dyed hair, and “Batman paraphernalia” was found in his apartment, which led many to leap to the conclusion that this was another case of movie-inspired violence. But the theory later fell apart: the shooter was not a Batman or Joker fan; his hair was dyed red, not green; the Batman mask in his apartment was likely purchased after he’d chosen which movie to attack. According to the Aurora trial prosecutor, the shooting could just as easily have happened during a showing of The Avengers or Jurassic World: “It had nothing to do, that we can find, with Batman.” In the past week, however, relatives of those killed at the screening have written a letter to Warners to express concerns about the film (“It is not the intention of the film, the filmmakers or the studio to hold this character up as a hero” was their response).

Ironically, media sensationalism – a very 2019 theme – is very much core to Todd Phillips’s Joker. DeNiro’s TV chatshow host is a significant, if inadvertent, catalyst for Fleck’s transformation. Meanwhile, the Gotham press eagerly spins Fleck’s first killings into a city-wide “kill the rich” class war. In one telling moment, Fleck spots an artist’s impression of a manically smiling “killer clown” on the front page of a newspaper. He adjusts his own smile to match it. Rather than transmitting the “craziness”, Joker is really interested in examining its causes, in the here and now as much as some alternative comic-book past. That necessarily entails empathising with its subject, and identifying lack of empathy as one of those causes. Sexual frustration might be another, but for all the buzz about incels, it is not the overriding theme. There is no simple explanation; it is more about an accumulation of factors, internal and external, that might drive a person, or a society, over the edge.

If that feels a little too dangerous right now, maybe it’s a sign of how close to the edge we are.

Joker is in cinemas from Friday 4 October