"Johnny Assmonkey" is the name that writer-performer Sophia Del Pizzo has given to her anxiety. In Assmonkey: In Conversation she tries to come to grips with both anxiety and depression, and particularly how they feed and are exacerbated by substance abuse.

The opening video segment is well-constructed, setting the slightly manic tone of the performance. Del Pizzo then opens with what is effectively a stand-up routine, singing a song about her vegan ex – “Alfalfa Male” – before introducing the first of a series of characters: Penelope, a teacher who's trying too hard to be cool. Each aspect of the performance is funny and works well in isolation, but it's not always clear what they add to the narrative.

The strongest section comes when Del Pizzo discusses substance abuse. She describes how it provides a brief break from anxiety, but goes on to recount – staying just the right side of lecturing – statistics that link addictions to depression. A video describes the different types of drugs (Uppers, The Drinky, The Trippy), their effects, and crucially, their after-effects. Yet, even so, when the central story ends with the tale (and video) of her crawling on stage to perform at a festival, if comes across as hilarious rather than tragic.

And that gets to the crux of the matter. Assmonkey is very funny, but it lacks something important for balance. There simply isn’t the jeopardy to give the show the depth it needs – so the substance abuse seems like too much fun, and the comedic sketches trivialize the anxiety.

Except that there is jeopardy, and plenty of it. The realisation comes in a tremendous double-whammy of an emotional gut-punch late on. But oh, so late. Too late.

We’re much better at talking about mental illness than we used to be, but it’s still a difficult topic, particularly as Del Pizzo is bringing her own experiences to the stage. Leaving the big eye-openers to the end is a mistake, and the show as a whole seems lacking in narrative structure. If we'd been given one of those revelations in earlier we'd have had the sense that Del Pizzo is in real danger, lending the humour the dark edge that it needs, and adding bite to the satire of well-meaning so-called experts portrayed in the character sketches.

As a performer, Del Pizzo is captivating: she’s in total control of the stage. And there is so much great material here – never a dull moment – yet there’s so much more to come. Sometimes you give a show three stars, but you’d really like to see it again in the future because there's evident potential still to fulfil. This is one of those moments.