Sleep deprivation is an effective form of torture that can break even the strongest wills.
It is associated with impulsivity, lack of empathy and a failure to adequately process information. According to Professor Russell Foster, head of the Sleep and Circadian Neuroscience Institute at Oxford University, when we try to think between 4am-6am our reasoning is as impaired as if we have been drinking alcohol.
Despite that, world leaders have been hammering out agreements of global significance - over Greece and Iran - in the early hours of the morning.
On Tuesday it was announced that after a 12-year-long stand-off US and Iranian diplomats had finally reached a deal granting Tehran sanctions relief in exchange for curbs on its nuclear programme after meeting after midnight to complete the agreement.
The deal comes after the news on Monday morning that a deal on terms Greece must meet for another bailout had been struck after a 17-hour all-nighter of negotiations in Brussels.
Speaking about the Greece deal, Foster told the Independent:
"[The leaders] would have been functioning when the brain is not well adapted to function... The fact that they were working in the early hours of the morning meant they could not possibly work at optimum performance."