It seems that sleep pattern variation is an evolutionary consequence of the survival benefit of having someone awake when others are sleeping [1]. A good combi

It seems that sleep pattern variation is an evolutionary consequence of the survival benefit of having someone awake when others are sleeping [1]. A good combination of night owls, insomniacs, and early risers in camp probably made it far less likely a sleeper got hauled off by the hyenas. This also seems to be the reason that anxiety (sense of danger) reduces our sleep. There's a part of our brain that doesn't differentiate well between today's worries and predation risk. For this reason, I think that addressing anxiety is often the best way to improve sleep. [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4972941 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4972941