The 12 boys and their football coach trapped for 10 days in a partially flooded cave in Thailand will be suffering psychological and physical impacts of their ordeal.

Stanford University fellow Dr Seema Yasmin told CNN the boys would have been afraid no one would ever find them, and even after being found they would still be fearful about how, or even if, they could be rescued.

"There are rising water levels and rising mud levels that do impose an impediment to those wanting to rescue those children and their coach. And they might also have an understanding that it might be tricky to get them out of there. So there's still that trauma," Yasmin said.

AP The moment rescuers found the 12 boys and their coach, after they had spent 10 days in the flooded cave.

Being unable to differentiate between night and day, group members would have lost their circadian rhythms, which were important for many biological functions.

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Having not had much food or water, could be a medical concern even after rescue because of the refeeding syndrome, Yasmin said. The syndrome can be fatal and is caused when people start earing after a period of malnourishment.

AP Luis Urzua, centre, the 33rd and final Chilean miner to be rescued after 69 days underground in 2010.

It is caused by sudden shifts in the electrolytes that help metabolise food.

Much of what was known about such situations came from the ordeal of 33 miners trapped nearly 500 metres underground for 69 days in Chile in 2010.

Once the miners had been rescued they struggled going back to a normal, healthy life, Yasmin said.

GETTY The cave the boys are trapped in would have been in darkness.

Talking about the case of the miners, survival psychologist Dr John Leach, of the University of Portsmouth, told the Daily Mail that when the mine collapsed most people would have tended to freeze, then go into a flight mode, and lastly a fight mode.

After a disaster, people go into an impact phase, where they realise something has gone wrong but may not comprehend it. People could continue with their normal behaviour, even if it didn't apply to the situation.

In some cases there could be a phenomenon called perseveration, where the part of the brain needed to take a new action stopped functioning. In that case people could keep repeating the same action.

For survivors the second day would be the "longest" and the third the hardest psychologically. By the fourth day brain and body should have adapted to the new environment and accepted it, and changed behaviour to the new routines.

Around the third week in a survival situation, people tended to hit a psychological low point, known as psychogenic death. Some people tried suicide.

Leach said every survivor he had spoken to who lacked food reported having constant hallucinations about it.

AP The second day was the longest for the miners, the third the hardest psychologically.

After the miners were rescued, all had shown symptoms of PTSD, but they should recover and lead normal and functional lives.

Cave diver Xisco Gracia was trapped in an underwater cave in Mallorca for 60 hours in 2017. He waited in a chamber about 80 metres long, 20m wide, and with 12m between the water and ceiling. He used his torch sparingly while he waited to see if his companion had made it out to get help.

He told the BBC he was hopeful for the first seven or eight hours, then started to lose hope, thinking his friend had failed to get out.

AP It was hard for the rescued miners to go back to a normal life.

He managed to remain calm but started to feel the effects of breathing in high levels of carbon dioxide. He had a headache, was exhausted, and was hallucinating. He lost track of time but thought he had been trapped for days, and at one point began thinking he was going to die without food or air. He considered his knife as a last resort, to choose whether to die quickly or slowly.

Former navy diver Rob Hewitt remarkably survived three days and four nights drifting at sea off the Porirua coast in 2006. He became separated from his fellow divers, and as night fell on the first day he began to lose hope.

As he drifted, he ate the kina and crayfish he had caught to stay alive, and prayed. He was aware his lice-covered body had started to absorb saltwater and decompose. His mental health deteriorated and he decided to let a nearby shark kill him if it approached.

STUFF Rob Hewitt hallucinated that he was buying a Coke from a dairy after four nights in the water.

Shortly before being rescued he had wild hallucinations, wandering ashore and into a shop for a can of coke, thrashing around in his wetsuit to find his wallet to pay for it.

Two cave explorers who intentionally spent long periods alone in caves in the French Alps found they slept for many hours at a time.

In 1965, Josie Laures spent 88 days alone in the cave, and Antoine Senni 126 days. The did keep in touch with researchers but were given no clues about passing time.

According to The Atlantic, their sleep schedules "got wacky". Senni would sleep for 30 hours then wake up believing he had taken a short nap. When they came out they thought they had spent weeks less in the cave than they thought they had.