How long can a man survive underground without going insane?

A traveler is buried under stones in a cave system. His only sources of food are mushrooms and creatures that live in the caves. Some of them will try to eat him. He has a source of light and heat that also scares the dangerous animals.

Given the fact he is highly intelligent while the animals are not, and the fact that he has Medieval Age technology, how long could he survive without going fully insane?

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    $\begingroup$ Not long: In the pitch black, he is likely to be eaten by a grue. $\endgroup$
    – user535733
    Mar 16, 2019 at 16:40
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    $\begingroup$ It is not exactly the same as in the question, but there is a house in Las Vegas that is totally underground, the house and its yard being in a space carved out of rock underground. The person who paid for the house was not expecting to go insane very soon. Of course it is a much better place to live in than a cave. forbes.com/sites/jimdobson/2019/02/09/… $\endgroup$ Mar 16, 2019 at 17:15
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    $\begingroup$ Note that the original title was misleading and asked about survival. The body of the question was clearly about psychological effects, so I edited the title to match. $\endgroup$
    – Cyn
    Mar 16, 2019 at 18:08
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    $\begingroup$ @GrandmasterB there is a reason solitary confinement is considered such a severe punishment, and in Western countries a prisoner in solitary still has some human contact (eg when meals are brought) and is not in constant life-threatening danger. Having no human contact or support in a disorienting, dangerous situation will break anyone, the only question is how long it will take - which is why the OP is asking! $\endgroup$ Mar 18, 2019 at 12:20
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    $\begingroup$ @KerrAvon2055 This is not directly equivalent to solitary confinement, First, I understand the cave system allows extensive exploration, secondly the survivor has more control over his activities, third there is extensive evidence that contact with other animals (therapy dogs, for instance) can be a substitute for human contact, fourth at America's highest security prison, inmates are left in solitary confinement for the rest of their life (decades), with zero hope of ever getting out, but their environment does not mentally challenge them for survival the way this one would. $\endgroup$ Mar 18, 2019 at 15:05

3 Answers 3


According to studies on everyone's favorite test subject—college students—the answer is: no more than 7 days.

Studies on human subjects are rare — in part because most modern universities would never consent to them — but in 1951 researchers at McGill University paid a group of male graduate students to stay in small chambers equipped with only a bed for an experiment on sensory deprivation. They could leave to use the bathroom, but that’s all. They wore goggles and earphones to limit their sense of sight and hearing, and gloves to limit their sense of touch. The plan was to observe students for six weeks, but not one lasted more than seven days. Nearly every student lost the ability “to think clearly about anything for any length of time,” while several others began to suffer hallucinations. “One man could see nothing but dogs,” wrote one of the study’s collaborators, “another nothing but eyeglasses of various types, and so on.”

While this study is problematic due to questions about the ethics of McGill researchers at the time, it is widely cited. Other studies about social isolation (solitary confinement) with or without sensory deprivation (in both humans and animals) come to similar conclusions about mental state (though not necessarily hallucinations).

This wasn't being trapped underground, but it seems like a reasonable approximation. The difference is that the graduate students knew they were safe and getting out. Your character doesn't know if he'll ever be rescued and is likely to just give up after a while.

Now, if your character were trapped with a group of people, the answer is months. A group of Chilean miners were trapped underground for 2 months, with the first part of that being without anyone knowing if they were alive and without any evidence they might be rescued. After that they had communication with the outside world and a conduit for food and supplies, though only a small hope of a successful rescue. After their amazing rescue (every one of them survived), they had psychological issues, but not insurmountable ones.

In another case, a man who was trapped underwater for 3 days but survived continues to have nightmares and has vowed never to return to the ocean. He was in a shipwreck and was rescued by divers working to recover bodies from the wreck. He had no contact with other people, no realistic hope of rescue, no light (after his flashlights died), almost no food or water (just a soda), and horrible conditions.

Being alone, being in the dark, not knowing if rescue is possible, those are all things that worsen the effect on the mind.

  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$
    – L.Dutch
    Mar 18, 2019 at 15:33

With heat, might, food, water, breathable air, and most important, shelter, this person can be in it for the long haul. Indefinitely, I would say, the limitation is his own - disease, being eaten, misfortune.

Humans have survived years in such conditions. Being in a cave or on an island makes little difference. The other animals are there to keep him company - and the added challenge, to keep him sane, is to outwit them to stay alive.

The only factor we do NOT know, is the state of his mind and the fragility of his own psyche. Does he have a reason, and the will, to survive?

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    $\begingroup$ Do you have some examples of humans surviving years in such conditions? (Islands seem different because you can see during the daytime, while underground you can't unless you have your own light source.) $\endgroup$ Mar 17, 2019 at 22:01
  • $\begingroup$ @ Monica Cellio I am thinking of the Japanese soldier who came out of the jungle decades after the war was over. He lived in absolute isolation. The only difference between a jungle and a cave is that a cave provides its own shelter against the elements and would therefore be more comfortable, so long as the survivor did not have claustrophobia. That is the fragility factor. $\endgroup$ Mar 18, 2019 at 0:07
  • $\begingroup$ He is kinda trained to survive in such conditions $\endgroup$ Mar 21, 2019 at 9:14
  • $\begingroup$ @Edward Constantin And again that is the human fragility factor. How experienced was this person at survival skills? How well trained? What was their motivation, their will to live? All personal factors that would have a greater effect than the situation itself. $\endgroup$ Mar 21, 2019 at 13:45

As long as the traveler has light, there can be some hope of using the intelligence to survive. Once in the darkness he will be as dumb as a stone against the darkness dwelling predators.

With medieval technology a light source will last at most few hours (oil burner, wooden torch). That's also, give or take, the lifespan the traveler can count on.


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