There’s an intriguing philosophical quandary at the heart of Jacob Marx Rice’s (not to be confused with Jacob Rees-Mogg) play. As our personalities are essentially chemical formulas, is a medicated man and woman, wrestling with mental illness, their true self or an idealised pair of pharmaceutical experiments living on borrowed time? Is it desirable to start a relationship under therapy, in a state of unstable transition, buoyed by yellow bentines, in pursuit of a doctor sanctioned best self? Or would such a union be a by-product of a false consciousness?

This sets up an inevitably heartbreaking scenario in which a manic self-harmer meets a wry depressive with barely suppressed suicidal tendencies; two self-harming, intelligent people who are dependent on drug regimens to function normally.

In an enclosed set, a box of sorts, like the one we put those suffering from mental health problems in; adorned with neutron-signifying electrical wires and bulbs; Steph and Jamie’s (Caoimhe Farren and James Mea) relationship plays out – first with caution and defensiveness, then with self-awareness tested, then with boundaries reset, then with defences lowered, and finally the beautiful highs and inevitable lows of disfunction and tragedy as their respective illnesses take hold.

The simple shorthand would be Romeo and Juliet with added psychoanalysis, but the play’s more ambitious than that – it’s out to document how terrifying abstractions like depression and self-harm disrupt and derail lives, sabotaging happiness, and how self-recognition of the dangers does little to avoid them. Add to this Catch-22, the ignorance and judgement of others, and you’ve got a path to true love laced with landmines and charity muggers. Puts your relationship failings – namely being selfish and thoughtless, in perspective, doesn’t it?

The Finborough have laid on an involving, emotionally harrowing two-hander; performances that add complexity and vulnerability to a couple of likable but shaky lovers. You root for them, you worry about them, then you worry about them some more, particularly in the tough latter stages when the writing , with the imprimatur of lived experience, grips the heart and twists the gut.

Chemistry is a challenging play with no clean answers to the quandaries it raises, and no comfort for those who’ve suffered as these characters suffer, or have been close to those with similar problems. If the production errs, it’s in the use of mawkish American folk pop, as the soundtrack to certain transitions. It’s the equivalent of telling the audience how to feel when the performances provide all the priming required. Regardless, Chemistry is an at times unsettling, but always compelling evening. It humanises the stigmatised and touches the soul using a wonderdrug – intimate performance.