t might feel like Issy Wood is staring right back at you, glaring out of every canvas, making hard, uncomfortable, unflinching eye contact. But she's not. The young British painter is staring at herself, lost in soul-searching rumination. You've just walked in at the wrong time.

This display at the National Portrait Gallery – the first in a new series of presentations looking at contemporary artists' use of portraiture – is Wood's first big public foray into capturing her own face. She's painted self-portraits before, but never at this scale, never this big and personal. For years now, her focus has mainly been on external stimuli: Diet Coke cans, antiques, clocks, ceramics, leather coats. The stuff of midnight doomscrolling, obsessive research, fetishistic desire. Seeing her close-cropped, soft-focus approach to everyday ephemera over the years has been like spying on someone's internet tabs, peeking into the diary of a bored, sad, overtired, caffeine-wired young overachiever.

She never really needed to paint her face because her work was always so obviously personal and diaristic. But she's done it anyway, and the results are tense and heightened. She's taken the same close-cropped, fuzzy, angular compositional approach, but now it's all skin and lips and tears. She sips a Diet Coke while doing a goopy, wet face mask in one enormous painting, squidges her cheek against a mirror in another, doubling her twisted reflection. She bleeds from her cheek and eyebrow in some smaller works, leans forlornly against her guitar in others. One painting catches her mid-sob, blurry-eyed and disconsolate.

Every painting here is her looking back at herself, lost in navel-gazing, self-pitying introspection. Two pictures of her as a kid are full of smiles and giggles, but they just make you realise how miserable the rest of the images are, and how miserable she must be. And that's not a bad thing in art terms (but probably not great on a personal level) because it makes for some really good paintings. They're weird, suffocating, intimate things, like you've been allowed into her weakest moments, like you're interrupting her mid-weep. You feel like you have to back out of the gallery quietly to let her get on with it.

This makes it all sound bleaker and more maudlin than it is. There's a humour to the work, a bit of silliness at points. In one painting, she's framing her face with plastic stick-on monster fingers, like she knows this is all a bit overblown.

It's surprising that she's not had more major institutional attention, because she's not just good, she's quietly important. A whole load of close-cropped, dark, woozy imitators have come out in her wake. She's a market darling, and I think we'll look back on her in a couple of decades as the ultimate zillennial painter.

Few artists manage to capture the crushing, endless, tedious anxiety, the malaise and ennui of the contemporary western condition like Issy Wood. This is the art of the bored, the medicated, the perpetually online, the depressed overachiever who feels like no matter what they do, they'll never be happy. And as uncomfortable as it is, the mirror she's squashing her face against here actually reflects us back on ourselves too.