Built to keep you scrolling: what the research says about Instagram, TikTok and your brain

How a feed holds your attention

Instagram, TikTok, Snapchat and YouTube make most of their money from advertising, so what they sell is your time: the longer you stay, the more ads they can show. Their feeds are built for that, and less and less of what they show comes from people you know. In April 2024, Meta said that for the first time more than half of what people saw on Instagram was recommended by its AI, and that Reels alone took up half the time spent in the app (Meta, 2024). A year later, a slide Meta showed in the US government's antitrust case against it put friends' posts at 7% of what people view on Instagram, down from 11% in 2023 (The Keyword, 2025).

Four design patterns do most of the work (Montag et al., 2019).

Unpredictable rewards

Each refresh might bring something good, or nothing. Tristan Harris, a former design ethicist at Google, compared checking a feed to pulling a slot machine's lever (Harris, 2016). In reinforcement experiments, rewards that come unpredictably keep behaviour going at a high, steady rate that's hard to stop (Ferster & Skinner, 1957), and gambling machines are engineered around exactly that (Schüll, 2012). Social media follows the pattern: across more than a million posts by over 4,000 people, including on Instagram, people posted sooner after getting more likes, as a reward-learning model predicts, and an experiment showed that the likes caused it (Lindström et al., 2021).

Nowhere to stop

Infinite scroll and autoplay remove the natural ends, like the bottom of a page or the end of an episode, where you'd decide whether to carry on. Aza Raskin, who designed infinite scroll in 2006, later compared engagement-driven design to sprinkling behavioural cocaine over an interface (BBC, 2018).

Approval on a schedule

Likes, comments, streaks and notifications turn other people's approval into a stream of small rewards. In 2017, Facebook's founding president, Sean Parker, described the company's products as a social-validation feedback loop, exploiting a vulnerability in human psychology, and said its founders understood this and did it anyway (Engadget, 2017). The same year, Chamath Palihapitiya, who had led user growth at Facebook, said the short-term, dopamine-driven feedback loops his industry had built were destroying how society works (The Verge, 2017).

A feed that learns you

Recommendation systems learn what you can't scroll past, and show you more of it. European regulators call the result a rabbit-hole effect (European Commission, 2024). In a brain-imaging study, videos that TikTok's algorithm had picked for each viewer activated reward and self-related brain regions more than videos picked for no one in particular (Su et al., 2021).

What happens in the brain

Brain scans show what this design taps into, but read them with care: they measure blood flow, not dopamine, and activity in a reward region isn't an addiction.

• Likes light up reward regions. When 32 teenagers looked at a simulated Instagram feed in a brain scanner, photos shown with many likes produced more activity in reward-related regions, including the nucleus accumbens, and the teens were more likely to like those photos themselves (Sherman et al., 2016).
• Habitual checking goes with a changing brain. Among 169 young teenagers scanned once a year for three years, those who checked social media more than 15 times a day grew more sensitive to anticipated social feedback over time, while those who didn't check grew less so. The groups already differed at the start, so the study can't say that checking caused the change (Maza et al., 2023).

Short videos and attention

A 2025 review of 71 studies with nearly 100,000 participants found that heavier use of short-form video, such as TikTok, Reels and Shorts, went with poorer attention and impulse control, and with more stress and anxiety. The links held for young people and adults, and across platforms (Nguyen et al., 2025). They are correlations, mostly from one-off surveys, so they can't tell whether short videos wear down attention or whether distracted, stressed people watch more of them.

Small experiments point the same way. In a lab study of 60 people, those who spent a ten-minute break scrolling their own TikTok feed were then worse at remembering to carry out a planned task than those who rested, scrolled Twitter or watched a YouTube video (Chiossi et al., 2023). And in seven experiments with more than 1,200 people, skipping between videos, or forward within them, made people more bored, not less (Tam & Inzlicht, 2024).

Is it an addiction?

Not officially. Neither of the two main diagnostic manuals, the American Psychiatric Association's DSM-5-TR and the World Health Organization's ICD-11, includes social media addiction. The only behavioural addictions they recognise are gambling and, in ICD-11, gaming (APA). Researchers speak of problematic social media use instead: addiction-like symptoms, such as failing to cut down or neglecting other things. By that measure it's growing among teenagers. In a WHO survey of about 280,000 children aged 11, 13 and 15 in 44 countries and regions, it rose from 7% in 2018 to 11% in 2022, with girls at 13% and boys at 9% (WHO Europe, 2024).

What the companies' own research found

Most of what's known about the companies' own findings came out through leaks, whistleblowers and lawsuits, not from the companies themselves. Some of it is allegation, and the companies dispute much of it; where they do, we say so.

Meta: Instagram and Facebook

Teen girls and body image. In 2021, the Wall Street Journal published Instagram's internal research on teenagers, the first of what became known as the Facebook Files. A 2019 slide said: We make body image issues worse for one in three teen girls. Another said teenagers blamed Instagram for increases in anxiety and depression, without being asked. And among teens who reported suicidal thoughts, 13% of British and 6% of American users traced them to Instagram (Wall Street Journal, 2021). Meta replied that the one in three were girls who already had body image issues, of whom 22% said Instagram made them feel better and 45.5% said it made no difference; that on 11 of 12 issues, more teen girls said Instagram helped than hurt; and that the research measured perceptions, not causes, sometimes in focus groups of 40 teens (Meta, 2021).

The whistleblowers. Frances Haugen, the former Facebook product manager who took those documents, told a US Senate subcommittee in October 2021 that the company's leaders knew how to make Facebook and Instagram safer but wouldn't, because they put their astronomical profits before people (US Senate, 2021). Mark Zuckerberg replied that the idea that Meta put profit over safety was not true. Two years later, Arturo Béjar, a former Facebook engineering director who later worked on Instagram's wellbeing, testified that in Instagram's own survey, one in eight users aged 13 to 15 said they'd received unwanted sexual advances in the past seven days, and that Zuckerberg never answered his warning (Béjar, 2023).

Hiding likes. From 2019, Instagram tested hiding like counts, a project known internally as Daisy. Internal documents show revenue falling by about 1% among people in the test, and that staff proposed launching it in March 2020 (Shorenstein Center, 2023). Instead, in May 2021, Instagram made hiding likes an option, with counts still shown by default, saying that hiding them helped some people and annoyed others (Instagram, 2021).

A study it stopped. In court filings unsealed in November 2025, school districts suing Meta say that in 2020 it ran a study with the research firm Nielsen, code-named Project Mercury, in which people who stopped using Facebook for a week reported less depression, anxiety, loneliness and social comparison. According to the filing, Meta ended the work without publishing it, and one of its researchers compared staying quiet to the tobacco industry. Meta says the study was stopped because its method was flawed, and that the filing cherry-picks quotes (Reuters, 2025). These are allegations, not findings.

Tweens. At the first social media addiction trial, in Los Angeles in 2026, jurors saw an internal Meta document that said: If we wanna win big with teens, we must bring them in as tweens. Another showed that 11-year-olds were four times as likely to keep coming back to Instagram as to competing apps. Zuckerberg told the jury that keeping young people safe had always been a priority (NPR, 2026).

Moods for sale. In 2017, The Australian reported on a Facebook presentation shared with an advertiser, which said the company could tell when young people felt worthless or insecure. Facebook said the research was never used to target ads, and that it doesn't offer tools to target people by emotional state (Facebook, 2017).

TikTok

In October 2024, 14 US attorneys general sued TikTok, accusing it of designing the app to addict young people. Kentucky's complaint was meant to hide TikTok's internal documents, but the redactions failed, and Kentucky Public Radio and NPR read them before a judge sealed it (NPR, 2024). According to the complaint:

• TikTok worked out that it takes 260 videos to form a habit. With videos as short as eight seconds, the investigators calculated, that can take under 35 minutes.
• TikTok's own research found that compulsive use goes with loss of analytical skills, memory formation, contextual thinking, conversational depth and empathy, with more anxiety, and with less sleep and less time for school, work and loved ones.
• The 60-minute daily prompt it set for teenagers cut their use by about a minute and a half, from around 108.5 minutes a day to around 107.
• An internal document said users are placed into filter bubbles after 30 minutes of use in one sitting.

TikTok said the complaint cherry-picks misleading quotes and takes outdated documents out of context, and pointed to the default screen-time limits and other protections it has for young users (NPR, 2024).

Documents released by Nebraska's attorney general in 2024 go further. They say that compulsive usage on TikTok is rampant, that young users have minimal ability to self-regulate effectively, and that TikTok saw its safety features as good talking point[s] (Nebraska Attorney General, 2024). In Europe, TikTok launched TikTok Lite in France and Spain in 2024 with a programme that paid users in points, exchangeable for vouchers, for watching videos (CNBC, 2024). After the European Commission opened proceedings over its addictive potential, TikTok agreed to withdraw the programme from the EU for good (European Commission, 2024).

Snapchat

Snapchat's best-known hook is the Snapstreak: a count of how many days in a row two friends have sent each other snaps, which resets if a day is missed. New Mexico's attorney general, who sued Snap in 2024, says its internal documents show the company knew streaks encouraged uncontrolled use, and quotes one employee: Wow, we should have more addicting features like this. The complaint also cites a Snap survey in which 45% of Gen Z users said they were on the app almost constantly (New Mexico Department of Justice, 2024). Snap disputes the claims. Independent research on streaks is thin: in a survey of 2,483 young Belgian teenagers, keeping streaks went with problematic phone use, though the links were weak (van Essen & Van Ouytsel, 2023).

Snap settled the first Los Angeles addiction case a week before the trial began (NBC News, 2026). In the Netherlands, a foundation that sued Snap in 2026 wants users to be able to switch off streaks, Snap Scores and autoplay (NL Times, 2026).

YouTube

YouTube was the other company the Los Angeles jury found liable, with 30% of the responsibility. Google says YouTube is a streaming service, not social media (NPR, 2026). Among the evidence filed in the federal case is a 2018 review, by YouTube's own user researchers, of studies on viewers' wellbeing. One slide says: Researchers feel that YT is built with the intention of being addictive, with autoplay and recommendations among the tricks to encourage binge-watching. Another notes that YouTube users control what they watch (YouTube, 2018).

Autoplay makes a measurable difference. In a randomised trial with Netflix users, turning it off cut daily viewing by about 20 minutes (Schaffner et al., 2025), and YouTube users say recommendations and autoplay are what most undermine their sense of control (Lukoff et al., 2021). The political rabbit hole is less clear-cut. Studies since YouTube changed its recommendations in 2019 find little sign that they push ordinary users towards extreme content, most of which is watched by people who already subscribe to such channels (Chen et al., 2023; Hosseinmardi et al., 2024), although one audit found recommendations drifting towards problematic channels for very right-leaning accounts (Haroon et al., 2023). Those studies are about politics, not about how long people watch.

Other apps. Lawsuits against Roblox and Discord are mostly about child safety rather than design that holds attention, so they aren't covered here. AI companion chatbots are the next front: the EU's proposed KIDS Act, below, would stop them from simulating relationships in ways that create emotional dependency.

What happens when people take a break

If feeds do harm, stepping away should help, and that can be tested: ask some people, chosen at random, to quit or cut back, and compare them with people who carry on. Dozens of these trials have now been run. Some of the largest and best known:

Pooled together, the trials give a consistent but modest picture. A 2025 analysis of 32 randomised trials with 5,544 people found small improvements in depression, anxiety, stress, self-esteem and wellbeing, but no reliable effect on loneliness or life satisfaction. How long the break lasted, and whether people quit or only cut down, made no consistent difference (Burnell et al., 2025). Another analysis, of ten trials, found that cutting down eased depression, and that quitting outright did no better (May et al., 2025).

History points the same way. When Facebook arrived at US colleges between 2004 and 2006, one campus at a time, students' mental health got worse, with more depression and anxiety, especially among those more likely to compare themselves unfavourably with others (Braghieri et al., 2022).

Self-control is part of the story. In a 2020 experiment, people given tools to set their own limits on social media and other apps cut their use by 22 minutes a day, and the economists behind it estimated that self-control problems account for about a third of the time people spend on those apps (Allcott, Gentzkow & Song, 2022).

Not every break helps, though. In some smaller studies, people who abstained felt no better (Hall et al., 2021), or felt lonelier and less satisfied with life (Vally & D'Souza, 2019), and five days off Facebook lowered people's stress hormone levels but also their life satisfaction (Vanman et al., 2018). A break that cuts you off from people can leave you lonelier, which is one reason to keep the conversations and drop the feed.

What's still debated

Researchers agree that social media can harm some people. They disagree about how much, and about how big a part it has played in the rise in anxiety and depression among teenagers since the early 2010s.

• Average effects look small. Across 355,358 adolescents in three large surveys, screen use explained at most 0.4% of the differences in their wellbeing: by one comparison, about as much as eating potatoes. That study covered screens of every kind, not social media in particular (Orben & Przybylski, 2019).
• Cause and effect may run both ways. The psychologist Jonathan Haidt argues that phone-based childhoods have caused an epidemic of teenage anxiety and depression (Haidt, 2024). Reviewing his book, Candice Odgers wrote that this claim is not supported by science: most of the evidence is correlational, and teenagers who are already struggling may simply use social media more (Odgers, 2024).
• The experiments are argued over too. One analysis of 27 experiments found an average effect close to zero (Ferguson, 2025); others, which count only trials where people cut back in daily life, find small benefits (Burnell et al., 2025).
• The best data belongs to the companies. Independent researchers can't see what people actually do on Instagram or TikTok, and most of what the companies found themselves has come out only through leaks and lawsuits.

What most agree on: effects differ a lot from one person to the next, compulsive use is a bigger risk than ordinary use, and even sceptics of the bigger claims, like Odgers, support making platforms safer by design.

What courts and governments have done

In the US, thousands of families and school districts, and nearly every state, have sued Meta, TikTok, Snap or Google's YouTube, arguing that their apps were designed to addict children. They argue about design rather than content, which US law largely shields. In 2026 the first of these cases reached juries:

Europe

The EU's Digital Services Act requires the largest platforms to assess and reduce the risks their design poses to users' mental health. In May 2024, the European Commission opened proceedings against Meta, concerned that Facebook's and Instagram's systems may stimulate behavioural addictions in children (European Commission, 2024). In February 2026 it found, preliminarily, that TikTok's infinite scroll, autoplay, push notifications and personalised recommendations breach the law, and that TikTok would need to change the basic design of its service, for example by phasing out infinite scroll (European Commission, 2026). It reached the same preliminary view of Instagram and Facebook in July 2026 (European Commission, 2026), and in November it found that TikTok's For You feed leads people into rabbit holes of harmful content (AP, 2026). None of these findings is final, and both companies dispute them. Fines can reach 6% of a company's worldwide turnover.

In September 2026 the Commission also proposed an EU KIDS Act. It would let children open their own social media accounts only from 15, and ban, for everyone under 18, addictive features including infinite scroll without stopping points, reward tricks, and push notifications during sleeping hours. It still has to be agreed by the European Parliament and EU governments (European Commission, 2026).

Australia and other countries

Since 10 December 2025, Facebook, Instagram, Threads, Snapchat, TikTok, X, YouTube, Reddit, Kick and Twitch have had to stop under-16s in Australia from having accounts. By June 2026, more than five million accounts had been removed, deactivated or restricted, and the government is doubling the maximum fine for systematic breaches to A$99 million (Prime Minister of Australia, 2026).

Others have followed. Malaysia has barred under-16s from opening accounts since June 2026 (Jakarta Post, 2026), and Indonesia began phasing out under-16 accounts on platforms it considers high-risk in March 2026 (New Straits Times, 2026). Turkey's ban for under-15s took effect on 1 November 2026, and its law also says that no service likely to make children addicted may be offered to them (Khaleej Times, 2026). Greece's under-15 ban starts in January 2027 (Al Jazeera, 2026). The UK plans to bar under-16s from spring 2027 and, for 16- and 17-year-olds, to switch on a midnight-to-6 a.m. curfew and switch off autoplay and personalised feeds by default (UK Government, 2026). France's parliament passed an under-15 ban in 2026, but its Constitutional Council struck it down as disproportionate (Conseil constitutionnel, 2026).

The lawsuits have spread too. In Canada, 14 Ontario school boards and schools are suing Meta, Snap and TikTok, saying their apps disrupt learning, and a judge let the case go ahead in March 2025 (Global News, 2025).

Public health

In 2023, the US Surgeon General warned that teenagers who spend more than three hours a day on social media face double the risk of symptoms of depression and anxiety, at a time when US teens averaged 3.5 hours a day; the advisory itself notes that the evidence is still incomplete (US Surgeon General, 2023). The next year he called for warning labels on social media, like those on tobacco (Murthy, 2024). Separately, the World Health Organization's survey of 44 countries and regions found problematic social media use among 11- to 15-year-olds rising from 7% in 2018 to 11% in 2022 (WHO Europe, 2024).

What you can do

You don't have to wait for the courts. The research suggests a few things that help:

• Take a break, and keep your friends. A week or more away from feeds helps a little, on average; cutting yourself off from people can backfire. Our guide: how to take a break from social media without losing your friends.
• Change your phone, not just your willpower. Switching off notifications, taking apps off the home screen and adding a pause before they open all reduced use in experiments. A time-limit prompt you can dismiss barely does, by TikTok's own figures.
• Keep the people, drop the feed. Unreeled, our free and open-source iPhone app, shows the people you follow on Instagram and nothing else: their stories, their posts newest first, your messages and your activity. There's no Reels feed, no Explore, no suggested posts and no ads. It's unofficial, and Instagram could restrict an account that uses it, so read about the risk first.

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