In her 40s, the comedian Shaparak Khorsandi has a revelation. All her life, she had been known as "Scatty Shappi", she writes in her new memoir - impulsive, socially clueless, prone to outbursts of temper. Then a professional declutterer came round for a BBC programme, took oen look at her house, and said: "Do you have ADHD?"

Suddenly, Shappi's life made sense. Her ADHD had made her over-eat, binge-drink, steal things, impulse-purchase wallpaper and skip her grandmother's deathbed in favoir of a one-night stand in Baron's Court. Wait, what?

Until recently, ADHD was considered a childhood disorder, more common in boys that girls. But in the last decade more adults have obtained a diagnosis (or diagnosed themselves). In showbiz, yuou can't throw a stick now without hitting somone who is presumably too distracted to notice it coming towards them.

Other comedians who have spoken about their attention deficit and hyperactivity issues include Ed Byrne, Josie Long, Robin Ince, Sue Perkins, Rory Bremner and Johnny Vegas. ("Soon," Khorsandi writes, "I think we will have a comedian writing a book about what it was like being diagnosed as not having ADHD."

Then there are Paris Hilton, Mel B and Lily Allen, the Loose Women panellists Denise Welch and Nadia Sawalha, Barbie director Greta Gerwig, Ant or Dec (it's Ant); and the model Katie Price, who announced her diagnosis on OnlyFans. The therapist Gabor Mate even diagnoses Prince Harry with ADHD on the basis of reading his memoir.

In Britain, it is both difficult and easy to get an ADHD diagnosis. Tricky on the NHS, where waiting lists are many years long, but very easy indeed if you have £1,000 or so to spend on a private appointment. When the BBC's Panorama sent a mildly scatty reporter undercover, three private clinics diagnoses him with the condition but an NHS doctor didn't.

One of the oddest recurrent themes of the celebrity ADHD discourse is how often it involves successful people insisting they're been held back in life. "I'm 38 now and I guess I felt I'm not realising my potential," said journalist Owen Jones in hsi coming-out video on the subject. (Yes, he went private, as did Khorsandi.) She uses exactly the same word, saying that gig reviews often noted that she did not "fulfil her potential". Really, though? Jones has a YouTube column, three books to his name and is on my telly with near-Rajanic frequency. What should he be- world king?

In a similar vein, Khorsandi has managed to write a book, which she attributes to procrastination followed by "last minute hyperfocus", aka the way that everyone writes a book. I'm not saying that her ADHD is not real or that she hasn't has a rough time, but I do question the wisdom of reinterpreting every event in her life, from finding divorce awful to not winning Pointless Celebrities, through the prism of faulty brain chemistry.

Much of the scepticism around adult ADHD is because it is now associated with worried middle-class overachievers having a midlife wobble, rather than dropouts, deadbeats or the truly marginalised. After a while, their testimony reads like boasting - look how much I overcame, I must be incredible - mixed with that strange post-X Factor sense that people can only be proud of achievements which have their origins in a struggle narrative.

Still, this memoir shows the good side of the recent uptick in ADHD awareness, which has relieved the shame and frustration of life's natural scatterbrains. They aren't lazy or thick; they just find things excruciating thatother people find painless.

The downside is pathologising normal variation - and common traits such as being selfish or annoying - or crowding out other explanations for bad behaviour, such as trauma. Khorsandi now takes amphetamines, but is a big advocate of therapy, arguing that pills "would not have helped me process the 1979 Iranian revolution, which had catapulted me and my family into exile."

Scatter Brain has two big things to recommend it. For those who can focus, Khorsandi fosters empathy for all those people out there with "pressure cooker brains" like hers. For those who can't, well... it's a nice short book.

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