Sombre documentary sees US soldiers give brave testimony while undergoing ibogaine and 5-MeO-DMT treatment to confront their traumas

A gaggle of former US Navy Seals open up about their post-traumatic stress in this absorbing if somewhat formulaic documentary by Jon Shenk and Bonni Cohen. Ultimately, it is something of an advertisement for a new therapeutic protocol that involves the veterans taking the hallucinogens ibogaine (derived from an African shrub) and 5-MeO-DMT (derived, like something out of a William S Burroughs novel, from a river toad); a treatment that, to hear the subjects here describe it, can work miracles on the battle-scarred, suicidal minds of its users. Currently, the treatment is only available at a Mexican clinic because the drugs have not been cleared by the US Food and Drug Administration, but a bunch of boffins connected to Stanford University’s Brain Stimulation Lab are studying its clinical effects and the film works hard to make everything look as legit as possible.

To be clear, we’re not necessarily questioning the drugs’ efficacy, but this particular film seems barely interested in the cognitive science and lets interviews with scientists with interesting glasses and fancy vocabularies stand in as guarantors that it all actually works. More persuasive is the testimony from the half dozen men we meet, who bravely discuss their pain and distress while the cameras roll.

Stephen King, Takashi Miike and Patton Oswalt are among the contributors to this documentary about Tobe Hooper’s 1974 horror masterpiece

If you’re programming your own little horror film festival in the run-up to Halloween, and Tobe Hooper’s stone-cold classic The Texas Chain Saw Massacre from 1974 is part of the lineup, then this would make a handy follow-up for a night’s viewing. It’s not a making-of movie, although there are snippets of insight into the production’s process; nor is it a meta-commentary at the same sprawling level of Room 237, the delirious doc about The Shining. Instead, Chain Reaction is something in between, constructed in five chapters featuring interviews with five very different, almost random-seeming interlocutors who have strong feelings about The Texas Chain Saw Massacre. These are: comedian Patton Oswalt, film-makers Takashi Miike (Audition, Ichi the Killer) and Karyn Kusama (Girlfight, Jennifer’s Body), academic Alexandra Heller-Nicholas, and writer Stephen King.

One may wonder why these five people are featured and not, say, any other bunch of opinionated famous movie buffs, but at least they have pretty interesting things to say. Each quilts together their own personal experience of the film with more general musings on cinema, technique, horror vo terror, and that annoying conversation stopper at every dinner party: the zeitgeist. We learn, for instance, that Takashi first saw Texas Chain Saw when he was 15, and chose it only because he couldn’t get in to see a rereleased print of City Lights by Charlie Chaplin. (He has still not seen the latter, he says.)

Mesmerising leads Hassan Najib and Elena Rivers play a pair of young hotel workers who carry out high-end robberies in this oddly unconvincing story

It’s not fair to critics who want to avoid spoilers but there’s a twist at the end of this romance-focused crime thriller that partly explains why everything that has come before has been so oddly stilted, unconvincing and thinly sketched out. Presumably, writer-director Felix Mackenzie was hoping to create a fairytale-like atmosphere but with a present-day London setting.

We’re supposed to feel enchanted by the tale of Lucan (Hassan Najib) and Alice (Elena Rivers), two crazy young kids pulling off heists while working day jobs as a bell boy and chambermaid, respectively, in a small hotel. But most viewers will just wonder why their high jinks are so incredibly unconvincing, why they trust their criminal mastermind handlers to show up with escape cars at exactly the moment needed, and why they live in a flat that looks as if it was hired on the cheap off Airbnb with practically nothing in the cupboards. Also, why does Alice walk out of her house wearing nothing but a skintight knit dress with no handbag or even a coat? Clearly, her mother (Amanda Abbington) brought her up to expect the entire world would be centrally heated. At least for most of the time she has sensible shoes on.