It’s not the dark hours the insomniac dreads but the clear light of day

The insomniac may come to dread the night’s solitude, but the next day poses the greater challenge. That’s when you are obliged to walk among the rested population and pass for one of them, when in truth most interactions are conducted in a state of self-doubting confusion; when harnessing one’s thoughts is like grabbing at shadows; the right words, if found, won’t cohere into fluent sentences; and dark intrusions from the subconscious flicker up and distract from whichever simple task you’re attempting to complete.

The novelist Samantha Harvey’s first memoir examines a year spent in this condition. It is littered with sharp insights expressed in exquisitely lucid prose but is as amorphous as its title suggests — which is fitting, given how sleep-deprivation distorts our mental framework, revealing the flimsiness of the cognitive structures built by the dormant mind.

Describing a period when she often remained awake for days, she seeks the causes and, where possible, their remedies. The death of a cousin, inner conflict over not having had children — a sadness, and yet she wouldn’t ‘want to make and love something that will die’ — and the EU referendum result: all precipitated her crisis, and (probably) all are irreversible.

But underlying issues might prove tameable, namely an anxious disposition stemming from childhood experiences, lingering resentment towards her father and a nagging scepticism about meaning and reality. ‘The problem with beginning to wonder if everything is a dream or simulation or illusion is that there’s no proof either way,’ she writes. ‘There’s nothing in the world or in your own body, mind or brain that you can point to as proof it isn’t. In this sense, it’s anxiety’s jackpot.’

These are anxious times. Recent years have brought greater honesty about the diverse ways our minds can debilitate us, and this book is timely in analysing a condition that defines our age. Anxiety’s correlation with our perception of time is discussed with reference to the indigenous Pirahã people of the Brazilian rainforest, who, Harvey says, live in the here and now, freed from abstract worry. They have few words for time and its passage, none for numbers, no sense of history beyond a couple of generations’ collective memory. As she tells it — relaying the controversial findings of the linguist Daniel Everett — their language is unique in featuring no recursion, by which sentences embed one thought within another. The Pirahã would not say: ‘When it rains, unless I shelter, I get wet.’ Instead, simply: ‘It rains. I shelter.’ There is, Harvey asserts, ‘none of this restless ranging from one hypothesis to another’.

This suggests that, for the rest of us, anxiety is entrenched by the linguistic formats that shape cognition and communication. Less scope for considering consequentiality implies less for self-doubt over the ramifications of one’s actions. If Harvey could only attain an Amazonian tribesperson’s state of being, worry would fall away... but instead she lives on a busy street in Bath, where she fixates on traffic noise while pursuing something that proves more elusive the harder she tries. ‘Sleep, damn you, sleep!’ the brain urges itself during the fraught nightly wait for the moment when ‘something bigger and stranger than yourself takes hold’.

Rather than settle, her skittish mind inquires and speculates. She learns French, compares faith in religion and in scientists’ expertise, dissects love and doubt, mulls over bereavements and braces for those to come, imagines putrefying bodies. Death obsesses her. In existential crisis she takes succour from Philip Larkin’s notion of ‘the million-petalled flower/ Of being here’.

The jumping around lends a disjointed quality, piecemeal as an insomniac’s memory. There is more rumination than narrative, though some emerges via an interwoven story exploring a bank robber’s anxieties, and a series of grimly funny dialogues with an unhelpful doctor. Harvey’s self-lacerating humour offsets the prevailing melancholy. ‘Any normal person can sleep; basic human function, not the work of gods,’ she writes. Elsewhere, while families in Syria sleep between airstrikes, she contemplates herself on

“a king-size mattress with [her] winter-togged duvet and... kelp-scented hair on a fake-down pillow under a bomb-free sky. What pea disturbs your sleep, princess? A passing Audi?

Eventually nature offers some salvation. River swimming brings calm and clarity, as does climbing a hilltop overlooking Bath on a luminous day in January. Like the snowdrops breaking through near her feet, she finds a small but irrepressible will to live. By the end, tentative optimism is displacing despair in humanity. Modern Britain may feel a hostile environment but a few delicately evoked moments remind her that most people try their best, in their quiet way. On nocturnally piecing together a jigsaw puzzle, she realises that a charity shop volunteer checked it was complete before placing it on sale. ‘Someone unpaid has counted these pieces so that nobody will be disappointed; so there’ll be less disappointment in the world. Maybe it’s not a bear pit.’

Most people are kind; it’s only that the unkind make more noise. It’s a thought to fortify an insomniac as another dawn approaches.