Who in the world doesn't like a party? Especially one with hats, party poppers, a raffle and a cake – all of which feature in Lauren Silver's upbeat, friendly show. The answer, it turns out, is Silver herself: she experiences an excess of anxiety, so that even happy social situations can trigger thoughts of death. She doesn't like surprises, and she doesn't like parties. A surprise party, then, is worst of all.

There are plenty of Fringe shows which feel like therapy for the performer, but this is the first one I remember which actually acknowledges it. As Silver explains, we're there to help with her Graded Exposure Therapy – a genuine form of psychological treatment, which involves subjecting herself gradually to the things she fears. And to make sure she's surprised during her own show, she distributes tasks among her audience: some are armed with oversized party poppers, some get to scare her with horror stories, some are even invited to choose the clothes she wears.

It looks anarchic – and the reliance on audience participation means the show will be better on some days than others – but the balance is a subtle and clever one. Overall, Silver gives up just the right amount of control. The scripted segments hover on the boundary between stand-up and theatre, fleshing out enough of Silver's back-story that she isn't defined by anxiety alone: the references to her Jewish heritage are entertaining, the cast of unseen characters she meets at the party are nicely drawn.

Much of this is played for laughs, but it's often informative too. After we've played a round of pass-the-parcel – no party would be complete without one – Silver spins it around, turning the final unwrapping into a funny but tense visualisation of what the same experience is like inside her head. A recurring dialogue with a recorded "inner voice" is witty and enlightening, and our own enthusiasm for party goodies is turned gently against us with a guilt-inducing sting in the tail.

Silver is an actor, of course, and we probably shouldn't believe absolutely everything we see. Still, her stories have the ring of truth to them – and although she laughs at her own reactions to the surprises, they sometimes still feel raw. I'd be lying if I said I was always comfortable with that, and I'm not sure I can fully embrace it as entertainment, but there's one thing I'm certain of: if Silver really is choosing to undergo therapy live on stage, it's no place of mine to say that she shouldn't.

A couple of segments feel amusing but disjointed, and the way that audience "volunteers" are conscripted through a raffle triggered some low-level anxiety of my own. But Silver floats along on a bubbly cloud of sheer likeability – and while the topics she tackles are serious ones, she delivers an hour of unforced fun. If the show's meant as therapy, I do hope it works for her. It certainly worked for me.