Gluttony, greed, sloth, satisfaction, envy, lust and anger are historically seen as the root of all evil. But can these undesirable behaviours truly stem from the biology of our brains? Neurologist Guy Leschziner believes so.
Last November, when he launched his e-book Seven Deadly Sins: The Biology of Being Human, and delved into the neuroscientific and psychological foundation of those human tendencies, the London-based professor inspired a lot debate. “The seven deadly sins are woven into the tapestry of what it is to be human,” he later wrote in The Guardian. “Each of these tendencies, at least in moderation or in specific circumstances, can be seen as a tool for survival.” He went on to say that the origins of the definition of those traits lies in evolutionary imperatives to protect the tribe they usually elevate extra of a organic query for us than an ethical one.
Neurologist and sleep doctor Guy Leschziner
| Photo Credit:
P.Okay. Ajith Kumar
A window into human society
“I was trying to understand how the brain, our biology, influences why we behave badly, and how a better understanding of these processes could actually give us opportunities to make the world a better place,” Leschziner tells The Hindu, on the sidelines of the Kerala Literature Festival 2025. “I study people at the extremes of the human experience to understand how their brains cause changes in behaviour and how it applies to all of us.”
In the introduction of the e-book, Leschziner explains how the previous 25 years of his life as a practising physician have supplied him a window into human society, permitting him to discover features of humanity that few outdoors the world of medication can see.
Leschziner’s grandfather was himself a sufferer of the deadly sins: he escaped Nazi Germany along with his brother, however their households perished in focus camps. At his clinic, Leschziner encounters sufferers from nations like Afghanistan, Syria, and the former Yugoslavia — “all in London as an outcome of war and upheaval, fruits of human sins”.
A advisor neurologist at the Department of Neurology and Sleep Disorders Centre at Guy’s and St Thomas’ Hospitals, in addition to London Bridge Hospital, the Cromwell Hospital, and One Welbeck, Leschziner is a determinist. “I believe that everything is a function of the connections within our brain and how it works,” he explains. “There are factors entirely beyond our control that influence how we behave. For some, it’s genetic; for others, it’s due to disease or disorder. But, for many, it’s shaped by what we’re exposed to — either in the womb or later in life — which fundamentally affects how our brains are configured.”
Making sense of sleep
Seven Deadly Sins is Leschziner’sthird e-book, and has gained crucial acclaim. However, initially, he had no intention of turning into an writer as he was busy along with his medical apply. A literary agent, impressed by Leschziner’s BBC radio sequence on the mysteries of sleep, persuaded him to pen his experiences.
Leschziner’s first e-book, The Nocturnal Brain: Nightmares, Neuroscience and the Secret World of Sleep, revealed in 2019, offered fascinating insights into the sleeping thoughts, as he drew on case research of his personal sufferers. The Scientist named it the finest neuroscience e-book of the yr, whereas Forbes termed it one among the must-read books of the yr.
He is glad that sleep is lastly receiving extra consideration in medical analysis. Throughout his exceptional profession, Leschziner has helped folks handle insomnia, sleep apnoea, stressed leg syndrome, and plenty of different sleep problems.
“When I was in medical school, we were taught nothing at all about sleep; it didn’t even figure on the curriculum,” says Leschziner, who was the scientific lead for the Sleep Disorders Centre, Guy’s Hospital, one among Europe’s largest sleep models, for over a decade. “There are entire generations of doctors who know nothing about sleep or were never taught its importance. Now we’re beginning to understand the far-reaching consequences of poor sleep on our physical, psychological, and neurological health.”
Shortcut to dementia?
He says that getting lower than the really useful seven to eight-and-a-half hours of sleep is a rising concern. “Sleep is crucial for every aspect of our daytime functioning,” says Leschziner. “We know it’s linked to high blood pressure, diabetes, weight gain, and there is increasing evidence that it raises the risk of heart disease and stroke. One major issue, which I believe will affect the entire world in the future, is the connection between sleep and dementia — especially as dementia is becoming more prevalent globally with ageing populations.”
Leschziner is equally intrigued by desires. “One of the major mysteries that remains is the function of REM (rapid eye movement) sleep — the stage we most closely associate with dreaming,” he says. “This stage is crucial for memory consolidation, moving information from the brain’s short-term memory circuits to longer-term storage. But REM sleep serves other roles as well; it is probably responsible for regulating our emotions. My own view is that, during sleep, we’re essentially creating a model of the world because we need it to make sense of our experiences.”
Though initially hesitant to wield the pen, writing has taken Leschziner right into a world past the hospital. “I chose a career in neurology after reading Oliver Sacks’ The Man Who Mistook His Wife For A Hat,” he says. “If my books can inspire even one person to study the brain, I’ll be very happy.”
ajithkumar.pk@thehindu.co.in
Published – May 31, 2025 04:32 pm IST
