‘Brain rot’ was named Oxford's word of the year for 2024, defined as the "supposed deterioration of a person’s mental or intellectual state" resulting from watching too much "trivial or unchallenging" content online, such as TikTok videos.
It's a term often bandied about in jokey fashion, but what if there's a grain of truth to it? That's the seemingly scary implication of a new study published by a large team of brain scientists based at Tianjin Normal University in China.
What did the study find?
They scanned the brains of more than a hundred undergrad students and had them complete a questionnaire about their habits of watching short online videos. The survey included statements like, "My life would feel empty without short videos" and "Not being able to watch short videos would be as painful as losing a friend," with participants indicating how much they agreed.
Intriguingly, researchers found that those who felt the most attached to short videos had noticeable differences in their brain structure. These participants had more grey matter in their orbitofrontal cortex (OFC) – a region near the front of the brain involved in decision-making and emotional regulation. Similarly, they had more grey matter in their cerebellum – a small, cauliflower-shaped structure at the back of the brain that plays a role in movement and emotions.
The team concluded this was bad news for lovers of TikTok as having an oversized OFC could be a sign of what they described as "heightened sensitivity to the rewards and stimuli associated with short video content". They speculated that watching too many TikTok videos might have led to this neural bloating.
Similarly, they suggested that a beefed-up cerebellum might help the brain process short video content more efficiently – possibly a result of frequent binge-watching. This could create a reinforcing cycle, where watching more videos strengthens these brain pathways, making the habit even more ingrained.
But that’s not all. The team also performed a second brain scan, tracking participants' brain activity while they rested with their eyes closed.
They found a greater synchronisation of activity within multiple areas of the brain. This included the dorsolateral prefrontal cortex (a region involved in self-control), the posterior cingulate cortex (an area involved in thinking about yourself), the thalamus (a kind of relay station for brain signals), and the cerebellum.
The researchers suggested these functional brain differences could reflect a range of problems among the more addicted participants. Issues include trouble disengaging from videos and a tendency for excessive social comparison while watching them.
They also asked the participants to complete a questionnaire about ‘dispositional envy’, a factor measured by how much they agreed with statements such as "I strive to reach other people's superior achievements".
Interestingly, the scientists found that many of the links between video addiction and brain differences were also tied to higher levels of envy. This suggests that feeling envious might make someone more likely to watch short videos – and, over time, this habit could lead to potentially harmful changes in the brain.
Does TikTok cause brain rot?
If you're an avid consumer of fun online videos – or maybe a concerned parent – the idea that watching habits could be reshaping brain structure is understandably alarming.
However, it is important to consider this study in a wider historical context in which new technologies and media have long provoked exaggerated neurological claims. It's also important to understand the profound limitations of the research.
It's nearly 20 years since The Atlantic magazine ran a cover feature that asked "Is Google making us stupid?" and the claimed answer, in a nutshell, was "Yes!". The author, Nicholas Carr lamented that he was once a "scuba diver in the sea of words", but now, thanks to Google, he zips "along the surface like a guy on a jet ski".
Countless brain imaging studies of dubious quality were also published in the same era, many purporting to show the calamitous effects of the World Wide Web on our fragile minds.
A few years later, neuroscientist Baroness Professor Susan Greenfield launched a media campaign arguing that "mind change" – the impact of the internet and video games on the brain – was as serious a threat to humanity as climate change.
She even wrote a dystopian novel about the internet’s dehumanizing effects, though it received mixed reviews (one critic even questioned if it was one of the worst science fiction books ever written).
Nearly two decades on, we're doing OK-ish – at least I don't think our brains have turned to mush. But of course, these earlier scares were before the advent of TikTok. Perhaps there is something uniquely damaging about the kind of short, scrollable, nonsensical content available today.
I asked Prof Peter Etchells, an expert on the psychological effects of digital technology at Bath Spa University if this could be plausible. "To the best of my knowledge," he says, "There isn't any good science to support the idea that short videos are specifically or uniquely bad in terms of effects on the brain."
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Could the short video brain study be that good science? Not really, the evidence suggests otherwise.
What did the study get wrong?
Let’s take a look at some limitations of the study. If the goal were to prove that watching TikTok harms the brain, a more effective approach would be to scan participants' brains before and after they consumed different amounts of the supposedly harmful content.
However, this study was entirely cross-sectional, meaning it only captured a single snapshot in time—there was no before-and-after comparison to show cause and effect.
Or, as Etchells puts it: "[From this study] you can't say anything about whether watching short videos causes changes in the brain, or whether certain types of brain structure precede certain types of video consumption.
"This study doesn't really add anything useful to our understanding of how digital technologies impact us."
Even if we accept the researchers' speculative leap that TikTok videos might have caused the brain changes they observed, there are still several issues to consider.
First, the researchers searched the entire brain for any differences that correlated with scores on the video addiction scale. This approach is a common issue in brain imaging research because it increases the risk of finding false positives. In other words, the more comparisons you make, the more likely you are to stumble upon random differences that appear significant but are actually just coincidences.
Second, even if we accept that the observed brain differences are real and caused by watching TikTok, interpreting them involves a great deal of speculation. The researchers framed increased synchronisation in the brain – known as regional homogeneity (ReHo) – as being a negative effect. However, ReHo itself is neither inherently good nor bad. In fact, other studies have linked increased ReHo in certain brain regions to positive outcomes, such as those observed in meditation training.
Perhaps the study's biggest flaw is its reliance on a questionable questionnaire-based measure of short video addiction, which lacks strong scientific validity.
As Etchells says: "Short video addiction is essentially an invented term, and is not a formalised, diagnosable clinical disorder."
Taken together, these issues suggest we shouldn't be overly concerned that TikTok is radically reshaping young people's brains in harmful ways.
That said, excessive time spent watching frivolous videos can still be problematic for some. However, rather than worrying about brain changes or addiction, it’s more productive to focus on developing healthier media habits.
"Often, when we see studies like this hit the news, it's a good opportunity to pause and reflect on whether we're happy with our tech use", says Etchells.
"If there are worries there, it's worth thinking about what you can do to weed out the things you're unhappy with while appreciating that we get lots of benefits from these technologies."
About our expert, Prof Pete Etchells
Pete is a professor of psychology at Bath Spa University. His research focuses on how playing video games and using social media affects our mood and behaviour. He’s the author of Lost in a Good Game and is currently researching whether game mechanics can encourage gambling behaviour in other parts of life.
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