Enlarge / HBO's The Last of Us provides a vivid visual imagining of what a Cordyceps infected human might become. (credit: YouTube/HBO Max)

HBO's new sci-fi series The Last of Us debuted earlier this week and is already a massive hit . Based on the critically acclaimed video game of the same name, the series takes place in the 20-year aftermath of a deadly outbreak of mutant fungus that turns humans into monstrous zombie-like creatures (the Infected, or Clickers). While the premise is entirely fictional, it's based on some very real, and fascinating, science.

(Minor spoilers for the series below.)

The first episode showed us the initial outbreak and devastation. Fast forward 20 years, and the world has become a series of separate totalitarian quarantine zones and independent settlements, with a thriving black market and a rebel militia known as the Fireflies making life complicated for the survivors. A hardened smuggler named Joel (Pedro Pascal) is tasked with escorting a teenage girl named Ellie (Bella Ramsey) across the devastated US, battling hostile forces and hordes of zombies, to a Fireflies unit outside the quarantine zone. Ellie is special: She is immune to the deadly fungus, and the hope is that her immunity holds the key to beating the disease.

Enlarge / Katherine Langford starred as Hannah Baker, a teen who dies by suicide, in the controversial Netflix series 13 Reasons Why . (credit: Netflix)

The controversial 2017 Netflix series 13 Reasons Why sparked years of contradictory academic studies on whether the show sparked a rise in teen suicides (suicide contagion, or copycat suicides ). Some showed negative impacts, while others found beneficial impacts. The most damning study appeared in 2019 , which reported a sharp increase in suicide rates among young people between the ages of 10 and 17 in the months after the first season's release—although it stopped short of finding a direct causal link between the two. In response, the streaming service edited out the original graphic three-minute bathtub suicide scene that ignited the controversy.

But Dan Romer, a psychologist at the University of Pennsylvania's Annenberg Public Policy Center who studies media and social influences on adolescent health, was skeptical about that 2019 study. His latest paper on the subject, published in the journal Suicide and Life-Threatening Behavior, found a seasonal pattern to teen suicide rates that seems to coincide with the school year, declining in the summer months. Taking this and other factors into account effectively eliminated the contagion effect reported in the 2019 paper. (For an in-depth look at the controversy and an overview of several of those studies, see my 2021 feature .)

As I've written previously , suicide contagion is a phenomenon in which exposure to suicide within a family, among friends, or through the media may be associated with increased suicidal behavior. There have been many studies over the years on suicide contagion—sometimes called the " Werther effect, " after the young protagonist of Johann Wolfgang von Goethe's 1774 novel, The Sorrows of Young Werther . However, the extent to which fictional portrayals of suicide may contribute to suicide contagion remains a matter of genuine academic debate .