Gino Evans makes his feature debut with this painful and disturbing drama which has some unwatchably horrible and violent moments. It’s set in Manchester and tells the story of a heroin user fresh out of prison and struggling to sort himself out. That might sound like a pretty standard beginning for gritty British social-realism, but with maturity and what looks like solid research, Evans turns his film into an examination of mental health issues. It’s not for the faint-hearted though, with some scenes in which people hurt other people very realistically.

Ex-Emmerdale actor Joe Gill plays Danny, who is released from prison into supported living after a short stretch for theft. Danny starts using again immediately, and he says in voiceover that he takes heroin to feel normal; it manages his OCD and intrusive thoughts (“I feel fucked up for even thinking them”). We are shown the intrusive thoughts that pop into his head: sitting opposite the manager of his supported housing, out of nowhere Danny pictures himself punching her repeatedly in the face. It’s brutal, and there are more scenes like this – realistic-looking and photographed with cold intensity by cinematographer Sam Cronin. I watched it clenched and tense – which is presumably the point, to show what it feels like to live like Danny, uncomfortably alert with adrenaline.

Gill gives a very good performance, his eyes telling the story of Danny’s shame and humiliation. One night, on his way to meet his dealer, Danny bumps into Laura (Becky Bowe), a mate from school, now pregnant and a sex worker pimped out by her controlling boyfriend. Smile-on-her-face cheerful, Laura is the least interesting character here; whatever she is thinking about her situation, we don’t get to know about it. It’s a shame, particularly in a film with an otherwise unwavering stare. This really is a tough watch.

• Treading Water is in UK cinemas from 25 April.