Princess Diana's brother Charles Spencer has offered a new explanation for some of the behaviour that surrounded his late sister, saying he believes she had undiagnosed ADHD and that the condition may have contributed to her intense sensitivity to rejection.
In his forthcoming memoir, Swan Song: Diana, My Sister, Spencer draws on childhood memories, school reports and his own experience of receiving an ADHD diagnosis later in life. He argues that some of the traits others interpreted as paranoia or emotional instability may instead have been connected to a condition Diana was never assessed for.
The book, published on 22 September 2026, revisits Diana's childhood, her rise to global fame and the immense pressure surrounding her royal marriage and public life. Spencer's comments about ADHD form part of a broader attempt to explain a side of his sister that he believes was frequently misunderstood.
Spencer Says Diana Had Similar Traits
Spencer's conclusion about Diana is retrospective rather than a confirmed medical diagnosis. He says he was diagnosed with severe ADHD later in life and recognised similarities between his own experiences and those of his sister.
In interviews surrounding the book, he has said he believes Diana had ADHD as well as dyslexia. He points to difficulties with spelling, word order and concentration as examples of traits he remembers from her childhood.
More evidence appears in Diana's school reports, according to extracts from the memoir. Teachers reportedly noted problems with concentration and restlessness from an early age, including difficulties remaining focused during lessons. One teacher described her as having a short attention span, while another wrote that her lack of concentration was affecting her progress.
Spencer argues that these difficulties were poorly understood at the time. Diana was born in 1961, decades before ADHD became as widely recognised and discussed as it is today.
'She Wasn't Paranoid'
One of Spencer's strongest objections is to the way Diana's emotional reactions have previously been interpreted.
He rejects the idea that she was simply 'paranoid', saying he believes her experiences were better understood through what he describes as her sensitivity to rejection.
Spencer has linked this to his own understanding of rejection sensitivity. In the memoir, he writes about experiencing an extremely intense emotional response to criticism and perceived rejection, and says he believes Diana experienced something similar.
The distinction is important because rejection sensitivity is not itself a formal diagnosis or an official symptom of ADHD, although the term is often used in discussions about intense emotional responses associated with the condition.
For Spencer, however, the concept helps explain why Diana could react so strongly when she felt abandoned, criticised or betrayed.
Why Diana Could 'Turn on a Pin'
The memoir also explores Diana's relationships with those closest to her.
Spencer recalls that she could fall out with people and then find it difficult to reconnect once she felt that someone had let her down. He says this included members of their own family.
Rather than presenting those incidents simply as examples of difficult behaviour, Spencer believes they should be viewed in the context of what he sees as an undiagnosed condition and the extraordinary pressure Diana was facing.
He describes her as someone who could 'turn on a pin' when hurt, while also stressing that her reactions were deeply emotional.
That interpretation forms one of the more personal elements of Spencer's account. He is not claiming to have medically diagnosed his sister, but drawing a connection between her behaviour and what he has learnt about his own ADHD.
Diana's Childhood Offers New Context
The childhood evidence is particularly significant because it moves the discussion beyond later speculation about Diana's personality.
According to reporting by a news media outlet, Spencer cites school records describing concentration difficulties and restlessness. He writes that Diana showed 'some of the key symptoms associated with ADHD' as a child, while also saying she was never tested for the condition.
His account also places those difficulties within the educational environment of the time. Diana attended schools in an era when learning difficulties and neurodevelopmental conditions were not understood in the same way they are today.
That does not establish that Diana had ADHD, but it provides the foundation for Spencer's belief that something significant may have gone unrecognised.
A Different Way of Seeing Diana
Spencer's argument comes as Swan Song presents an intensely personal portrait of his sister. Penguin describes the memoir as an account of Diana's life and death drawn from the perspective of the brother who grew up alongside her.
The book also revisits the intense media attention surrounding Diana and the pressures she experienced after becoming a member of the Royal Family. Spencer has argued that the public saw only part of what she was dealing with, particularly as her private struggles unfolded under relentless scrutiny.
His ADHD theory sits within a much wider portrait of Diana rather than standing alone.
Whether that interpretation changes how readers understand her remains open to debate. What Spencer offers is not a diagnosis, but a brother's attempt, nearly three decades after her death, to reconsider behaviour that he believes was too readily labelled as paranoia or volatility.
For Spencer, understanding Diana through the possibility of undiagnosed ADHD provides another explanation for why rejection could affect her so deeply—and why, beneath the global fame, she may have been dealing with difficulties that nobody around her fully recognised.
