For arthouse junkies, the young French-Canadian film-maker Xavier Dolan has long been the most exciting blot on the cinematic landscape. We say long: at 25 Dolan has five incredible motion pictures to his credit, populated by lively, funny, rude, raucous creations.

Mommy picks up where the Freudian psychodrama of Dolan's debut feature – 2009's How I Killed My Mother – left off: on the front line of squabbling mother-son relations. Opening text tells us it is 2015 and radical changes in Canada's health service allow for parents to leave problem children in the care of a public hospital.

Teenager Steve (Antoine-Olivier Pilon), we feel, is a prime candidate: an uncontrollable mess of hormones, ADHD and violent rages. Still, his doting, eccentric mother Diane (Anne Dorval) – herself a mess of lip-liner, tight jeans, and unpacked possessions – brings the boy home from a juvenile correction facility, where they form an unlikely friendship with Kyla (Suzanne Clément), a damaged, stuttering teacher from across the road.

Dolan's characters live and breathe like no others: they sing, dance, fight and swear like troopers. That goes double for Mommy, a film defined by cheesy pop, boozing, post-hip-hop cursing, hilarious antics and, some 75 minutes in, one of the most bravado cinematic devices ever committed to celluloid: we won't spoil it.

For all these uproarious shenanigans, there's a dark emotional core here to rival Dolan's more obviously probing works, Laurence Anyways and Tom at the Farm. The cause of Kyla's distress is hinted at in bedside photos; various physical fights are genuinely terrifying to watch.

Cannes (rightly) loves to honour the greats, and this year's programme is dominated by established talents such as Ken Loach, Mike Leigh, and Jean-Luc Godard. But if the jury can hold their nerve, then ladies and gentlemen, we believe we have a Palme d'Or winner.