Show Me the Science with Luke O'Neill

• The Science of Seasonal Affective Disorder

  Why do so many of us feel the gloom set in when the clocks go back and the days get short? In this week’s podcast, Luke O’Neill delves into the biology of Seasonal Affective Disorder, or SAD, a form of depression that appears in winter and lifts again when the light returns. First identified about fifty years ago in northern Europe, SAD affects around one in every hundred people severely, and up to one in five to a milder degree. Women are three times more likely to experience it than men. Geography plays a big part too: roughly 1% of people in Florida report symptoms, compared to 10% in Alaska. Around 7% of people here in Ireland can be badly affected each winter. Luke explains that it all comes back to our circadian rhythms — the body’s internal clock that runs on a 24-hour cycle. In low light, this rhythm can drift off course, affecting hormones like melatonin (which regulates sleep) and serotonin (which affects mood). The good news? Light therapy works. Recent studies show that 30 minutes a day in front of a light source of 10,000 lux can help reset your body clock and ease symptoms. For comparison, moonlight gives off just 1 lux, normal indoor lighting about 300, while a bright winter’s day can reach 20,000. So, step outside when you can — daylight is the best medicine. The Mayo Clinic also recommends using a lightbox for about 20 minutes within an hour of waking during the darker months. SSRIs, the antidepressants that boost serotonin, can also provide relief. Scientists even suggest SAD could have evolutionary roots, a leftover human tendency to “hibernate” through the bleakest months by conserving energy, withdrawing socially, and staying indoors. Luke ends on an optimistic note: winter may mess with our body clocks, but it doesn’t last forever — the light always comes back. ✨ This episode was suggested by listener John O’Reilly. 💡 Got a question or topic for Luke? Email him at 📩 [email protected]

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• The Science of Cellulitis

  This week, Professor Luke O’Neill turns his microscope to a condition he knows all too well — cellulitis. It’s one of the most common bacterial infections there is, affecting about one in every 500 people each year. The skin turns red, swollen, and sore, and you might even feel flu-ish as your immune system fights back. Left untreated, it can spiral into sepsis, making early diagnosis vital. Listener Joanie suggested this week’s theme, and you can do the same by emailing Luke at [email protected]. As Luke explains, cellulitis happens when bacteria slip through tiny breaks in the skin — a scratch, a cut, even an insect bite — and start multiplying. He suspects that’s how he picked it up himself earlier this year. Rates of cellulitis are on the rise, with hospitals seeing more admissions, especially in settings where people live in close quarters: nursing homes, homeless shelters, and college dorms. Obesity and antibiotic resistance may also be fuelling the increase. Treatment is straightforward (antibiotics usually clear it up) but prevention is even better. Keeping skin clean and moisturised, and treating any breaks promptly, can stop it taking hold. And it’s not just humans. Cats, dogs and even horses can suffer from cellulitis, with vets watching closely for swelling and lameness. In fact, that old-fashioned poultice once used to “draw out” infection still has its place — at least in the stable. From microbes to moisturiser, Luke explores how our skin keeps the world out. And what happens when it can’t.

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• The Science of Hallowe’en

  This week, Show Me The Science gets a little darker — and a little stranger. Professor Luke O’Neill dives into the science of Hallowe’en, tracing its roots back to the Celtic festival of Samhain, the ancient Irish celebration marking the start of winter — that “dead time” when the veil between worlds was said to thin. It’s not about ghosts and ghouls, Luke explains, but about remembering ancestors, lighting bonfires, and wearing masks to mark the turning of the seasons. Around those fires, people bonded, built resilience, and reaffirmed community — something modern psychology still recognises as vital in times of darkness and uncertainty. Luke explores the science of fear: how the body reacts when startled, from adrenaline spikes to endorphin release, and why a good fright, once we recover from it, can actually make us stronger. Researchers have even measured these effects in saliva! But don’t expect Luke to be queueing up for a horror marathon — he admits he doesn’t get the same thrill others do from being scared senseless. There’s also a scientific story behind our favourite monsters. The myths of vampires and werewolves, Luke reveals, may have stemmed from a rare inherited condition called porphyria, which causes sensitivity to light, red-stained teeth, and even hair growth and behavioural changes — symptoms that once seemed supernatural. And diseases like plague or tuberculosis, which sometimes left victims appearing to rise from the dead, helped fuel the legend of the undead. From Bram Stoker’s Dracula — possibly inspired by both the actor Henry Irving and the medical realities of syphilis — to the theory that “Dracula” could derive from the Irish “droch fhola,” or “bad blood,” Luke connects folklore, medicine, and etymology in classic Show Me The Science style. And there’s even a royal twist: King George III famously suffered from porphyria, and through royal intermarriage, the disease spread across Europe’s bloodlines — adding a touch of genetic truth to the vampire myth. This special Hallowe’en edition was produced in collaboration with the Music Technology course at South East Technological University. The haunting original music was composed and recorded by Billy Doran.

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• The Science of Regulatory T Cells

  Ever wondered what keeps your immune system in check when it starts misbehaving? On this week’s podcast, Professor Luke O’Neill explains the world of regulatory T cells—the immune system’s very own “military police.” These tiny guardians stop other cells from attacking the body, helping prevent autoimmune diseases and keeping us healthy. Luke takes us through the Nobel Prize-winning discoveries of Mary Brunkow, Fred Ramsdell, and Shimon Sakaguchi, who cracked the secrets of immune tolerance. Back in 1995, Sakaguchi discovered these remarkable regulatory T cells, proving that the immune system is far more sophisticated than previously thought. Brunkow and Ramsdell uncovered the critical role of the Foxp3 gene in autoimmune diseases, and Sakaguchi later linked the Foxp3 gene to the development of these life-saving cells. Luke even shares insights from a recent encounter with Sakaguchi himself! If you’ve ever been curious about how the body avoids attacking itself, or how groundbreaking immunology research leads to real-world insights, this episode is your backstage pass to the science of regulatory T cells. Got questions, ideas, or thoughts for Luke? Email him directly at [email protected]

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• The Science of Performance Enhancing Drugs

  An Irish Olympian has decided to take a bold and controversial leap. Swimmer Shane Ryan has retired from conventional competition to join the Enhanced Games, a new event where athletes will be allowed to use performance-enhancing drugs. In this week’s podcast, Professor Luke O’Neill looks at the science and the ethics behind this radical sporting experiment. The Games’ creator, Aron d’Souza, says he wants to celebrate human potential without the limits imposed by anti-doping rules. Backed by investors such as Peter Thiel and Donald Trump Jr, the Enhanced Games are due to take place in Las Vegas in May 2026, offering up to a million dollars for breaking a world record. Luke dives into the biology behind enhancement. He explains how testosterone builds muscle mass, how growth hormone boosts recovery, and how EPO (erythropoietin) increases red-blood-cell production and endurance. These substances can deliver extraordinary results, but they also carry dangerous side effects: heart damage, infertility, high blood pressure, diabetes, kidney failure, and even seizures. Beyond drugs, the Games will also allow prosthetic limbs and high-tech running shoes, pushing the boundary between sport and science fiction. Critics, including the IOC and US Anti-Doping Agency, say it will destroy fair play. D’Souza insists athletes will be medically supervised and screened for safety. Luke asks what this says about the times we live in — an “age of enhancement” where medicine, tech and ambition blur together. From longevity clinics to performance labs, we’re already chasing upgrades to our own biology. It might sound like The Hunger Games, but it’s very real — and it’s coming soon.

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