This article explains research and expert findings for general understanding. It is not medical advice and is not a substitute for it. Nothing here should be read as a recommendation to start, stop, or change any treatment, medication, supplement, or health practice. Evidence in this field often comes from laboratory or animal studies, or from early or limited human research, and findings can change as more research is done — where that applies, the article says so. If you have a health question or condition, talk to a qualified healthcare professional who knows your individual circumstances.

You can have a job, a family and a full week of things to do, and still be struggling in a way nobody around you can see.

Some days, the mind keeps circling a worry about something that has not happened. On other days, things you once enjoyed feel like too much effort.

Anxiety and depression are common. The World Health Organization estimates that 359 million people were living with an anxiety disorder in 2021, and about 332 million people had depression in 2021. These figures refer to disorders, not an ordinary worry or a bad week. [1][2]

Their causes are not simple. Genetics, childhood experience, trauma, illness and personal circumstances can all matter. The WHO describes anxiety and depression as arising from biological, psychological and social factors together. [1][2]

This article follows just one thread: the world a person now lives in. It is one thread, not the whole explanation.

To see why that thread is interesting, start with a tiger.

The Invisible Tiger

Imagine walking through a forest when a tiger steps out.

There is little time to think. The body reacts. The heart speeds up. Muscles prepare. You run or freeze. This is the familiar fight-or-flight response.

Now imagine the tiger leaves. The danger is over. The body can begin to settle.

The modern “tiger” is different. It may be a question:

What if I lose my job?

What if the test comes back bad?

What if the business folds?

Nothing has happened yet. But the question remains open.

Worry can work this way. The mind keeps looking ahead because there is no clear answer yet.

Researchers call one part of this difficulty intolerance of uncertainty. A 2026 preregistered meta-analysis combined 738 effect sizes from 115 studies and dissertations, representing 138 independent samples and 28,693 participants. It found a strong association between intolerance of uncertainty and worry, including substantial associations across several anxiety disorders. [3] This is evidence of association, not proof that uncertainty causes anxiety disorders.

The tiger is only a metaphor here. A job worry is not the same bodily event as facing a predator. The useful similarity is simpler: something feels unresolved, so the mind keeps watching for what happens next.

An unresolved possibility can be enough to keep the mind occupied.

When Reward Loses Its Pull

Now consider something less frightening.

A friend invites you to dinner. You expect the evening to be good. You have enjoyed evenings like it before.

Yet getting dressed and leaving the house feels strangely difficult.

One way to understand this is through anhedonia: a reduced ability to feel pleasure or interest in things that used to be rewarding.

Depression can affect several parts of reward processing. These include looking forward to something, valuing it, enjoying it and deciding whether it is worth the effort. Much of this evidence comes from laboratory and early clinical studies, and research is still developing. [4] A systematic review of 43 studies found that depression and anhedonia were associated with reduced willingness to expend effort for rewards, particularly physical effort. [5]

This does not mean reward explains depression. Depression is a complex set of problems, and reward is only one part of it. [4][6]

The important point for this article is narrower.

The dinner may still be good. But the pull toward it can weaken.

The mind is not necessarily unable to enjoy anything. The step that normally gets you moving toward something rewarding may simply become harder.

The Comparison That Never Ends

The third process is comparison.

People have always compared themselves with others. A neighbor’s house. A colleague’s promotion. A friend’s good news.

The instinct is old.

The environment around it has changed.

Imagine ending a decent day feeling satisfied. Then you pick up your phone.

Within a minute, you see someone’s promotion, someone’s holiday and someone’s new kitchen. Your own day has not changed. But the people you are comparing yourself with have.

And the next time you look, there will be more.

Research finds significant associations between social comparison and both depression and anxiety. [7] A separate 2023 review found associations among comparison, envy and depression on social networking sites. The limited studies that could examine direction also suggested that depression can increase comparison. [8]

This does not show that social media causes depression.

The narrower point is easier to make: digital networks have greatly increased how often, how widely and how easily we can compare ourselves with other people.

The comparison instinct is old. The comparison environment is not.

Three Processes, One Missing Off-Switch

The studies above do not make the connection that follows. The connection is my synthesis.

Three different processes may share one feature of modern life: the signals they respond to can remain available long after the immediate event.

The worry may not resolve.

The comparison does not run out.

The next possible reward is always there.

This is close to what researchers call evolutionary mismatch: a trait shaped under earlier conditions may behave differently when conditions change. [Glossary] That framework is established. The specific connection I am making here is narrower.

Modern life is not simply more dangerous than earlier life. In many important ways, it is safer. Earlier societies also faced disease, hunger, violence and early death.

The question is different.

What happens when a mind that responds to uncertainty, reward and social evaluation operates in an environment where those signals can remain available almost without pause?

The Missing All-Clear

An immediate danger has an end. When it passes, the body can begin to settle.

Modern worries are different.

A job problem can remain unresolved for months. Money worries can return every day. Messages and updates keep coming.

None of these things is necessarily harmful. They are simply part of modern life.

But there is often no clear moment that says: you can stop now.

That is the missing all-clear.

We do not yet know how much this matters to anxiety and depression. It cannot explain every case. Biology, life experience, illness and many other factors matter.

But it gives us another question.

Not only: “What is happening inside this person?”

But also: “What is this mind being asked to live with?”

Conclusion

Anxiety and depression cannot be blamed on modern life. This article does not make that claim.

Its smaller point is that modern environments can leave fewer natural stopping points for processes that respond to uncertainty, reward and social evaluation.

The mind does not exist apart from its surroundings.

We have become very good at building surroundings that keep the body safe. The harder question may be what kind of surroundings allow the mind to stand down.

Modern life has not made the mind weaker. It has made some of its oldest signals harder to switch off.

Glossary

Anhedonia — A reduced ability to feel pleasure or interest in activities that used to be rewarding.

Intolerance of uncertainty — A tendency to find uncertain situations especially difficult, threatening or distressing.

Reward processing — The mental steps involved in anticipating, valuing, experiencing and learning from rewards.

Social comparison — Judging yourself by measuring your abilities, situation or achievements against other people’s.

Evolutionary mismatch — The idea that a trait shaped under earlier conditions may work differently when conditions change.

Fight-or-flight response — The body’s fast, automatic reaction to a perceived threat, preparing it to confront or escape.

Systematic review / meta-analysis — Ways of combining existing research. A systematic review summarizes studies using a set procedure; a meta-analysis combines their results statistically.

Sources

[1] World Health Organization. Anxiety disorders. 8 September 2025.

[2] World Health Organization. Depressive disorder (depression). 29 August 2025.

[3] Akbari, M. et al. A hierarchical uncertainty framework of anxiety: Preregistered meta-analytic structural model of intolerance of uncertainty and worry across anxiety disorders. Clinical Psychology Review, 2026.

[4] Wang, S., Leri, F. & Rizvi, S. J. Anhedonia as a central factor in depression: Neural mechanisms revealed from preclinical to clinical evidence. Progress in Neuro-Psychopharmacology & Biological Psychiatry, 2021.

[5] Horne, S. J., Topp, T. E. & Quigley, L. Depression and the willingness to expend cognitive and physical effort for rewards: A systematic review. Clinical Psychology Review, 2021.

[6] Nielson, D. M. et al. Great Expectations: A Critical Review of and Suggestions for the Study of Reward Processing as a Cause and Predictor of Depression. Biological Psychiatry, 2021.

[7] McCarthy, P. A. & Morina, N. Exploring the association of social comparison with depression and anxiety: A systematic review and meta-analysis. Clinical Psychology & Psychotherapy, 2020.

[8] Carraturo, F. et al. Envy, Social Comparison, and Depression on Social Networking Sites: A Systematic Review. European Journal of Investigation in Health, Psychology and Education, 202