Big Mood review: Nicola Coughlan and Lydia West comedy is a triumph

Meanwhile, Eddie is about to lose her beloved bar Wet Mouth, which she inherited from her dead dad and desperately wants to hold onto as the last physical tie she has to him.

But at least they have each other – except Maggie's bipolar means that she's not someone her ride or die can ever truly rely on, particularly in a crisis, because she's so often having one of her own.

Big Mood never once diminishes the toll that Maggie's mental illness takes on her, the person who is actually living with it, but by being in Maggie's life, and as her closest confidante, Eddie is living with it too – although the writing takes care never to judge or lambast either for behaviour which is entirely human and so often unavoidable.

"I fix problems and you have them," says Eddie after Maggie's Love Actually-themed 30th birthday party is brought to a grinding halt by a gaggle of wayward rats, a ploy orchestrated by Maggie, who is trapped in one of her extreme lows and doesn't have it in her to ring in a new decade – just one of many instances when Maggie's mental illness rears its head.

In the first episode, a manic Maggie goes back to her old high school, accompanied by Eddie as her "publicist" 'Adele Dazeem', to give a talk on working in theatre after exaggerating her current situation.

But she's also there to seduce one of her former teachers, and their jaunt ends abruptly with the duo sprinting out of the front gates as a crowd gathers to process the almighty mess left in Maggie's wake.

In episode 3, she throws a dinner party in an attempt to convince her doctor that she can live a full, well-rounded life without medication, but the evening is a car crash.

Maggie serves up culinary delights including a lychee pasta bake from a Calum Best cookbook and a tiramisu that "smells like squid", before torpedoing her writing career further and almost running off to Cambodia with a man called Brian, who she started talking to on Tinder just one hour earlier.

Even in the midst of her most embarrassing, distressing and depressing moments, Whitehill's nose for comedy is impeccable – if you don't laugh, you'll cry, and you'll probably never stop.

But crucially, she never punches down or makes Maggie the butt of the joke, instead highlighting just how absurd and surreal living with a mental health disorder can be, which in turn dispels the god-awful, oft-parroted myth that "you can't say anything anymore".

As well as Whitehill drawing on her own mental health experiences, Bipolar UK also guided the production to ensure that the writing is as authentic and responsible as possible, and that's evident throughout.

Those who can relate will feel seen, even if their own experience of bipolar, either personally or through a loved one, manifests differently to Maggie's, or if they have another mental health condition altogether.

Those who have no experience of mental ill health will find it enlightening, whether that's learning how some people with bipolar can lose hours, even days, during a manic state, or how medication can impair creative function.

When Maggie's on lithium, she finds it impossible to write, but not taking her meds leaves her intensely vulnerable. And even when she eventually does as the doctor suggests and takes her lithium like a good little egg, much to her mother's relief, the pitfalls of not adjusting her levels when needed leave her in a precarious state, and threatens her friendship with Eddie, culminating in a conclusion that's bold and refreshingly messy – and hopefully means a second season is on its way.

Big Mood also takes the time to dispel harmful myths about certain mental illnesses that have dominated popular culture since time immemorial, such as people with schizophrenia not being predisposed to becoming serial killers.

"I am non-violent, never even swatted a fly," says a friend of Maggie's who she met during her time on a psychiatric ward.

While that particular conversation does feel like a scene lifted from an educational film rather than being organically weaved into the plot, sometimes simply spelling things out, particularly when navigating such important subject matter, is the best approach to take.

But while Maggie's mental illness and the impact that has on those around her is a key strand of the narrative, that's not all Big Mood is, just as her bipolar is a part of her, but not the full package.

Anyone who has suffered from mental ill health can relate to that.

The series is also about female friendship, toxic exes, strained parent-child dynamics, sibling tensions and turning 30, which often brings both identity and financial crises, all of which are universally understood in some capacity.

Weaved among that is punchy social commentary on the devastating pressures facing the NHS, which rears its head in episode 5, and the scourge of private property development in the UK's major cities, which is pushing out the people and businesses that made them truly great in the first place – all of which is deftly tackled in six 25-minute-a-pop episodes that are as amusing and silly as they are heartbreaking and sincere.

As well as sharp, singular and very funny writing teeming with immensely enjoyable pop culture references, credit must also go to Coughlan and West, who are perfectly cast in the lead roles.

The former, in particular, navigates what is undoubtedly the most challenging material of her career to date, showcasing just how extensive her talents are.

Coughlan could so easily have veered into caricature given the full spectrum of what's required of her, but she knows exactly when to lean in and when to pull back, cementing herself as one of the most versatile actors working today.

This is the second time Coughlan and Whitehill, who are close friends in real life, have worked together in a professional capacity, and long may their partnership continue.

Big Mood is available to watch on Channel 4 from Thursday 28th March at 10pm. Check out more of our Comedy coverage or visit our TV Guide and Streaming Guide to find out what's on.

Try Radio Times magazine today and get 10 issues for only £10 – subscribe now. For more from the biggest stars in TV, listen to The Radio Times Podcast.