Sleeping too much (a sleep surplus) is supposedly not harmful and, on the contrary, offers cognitive and physiological benefits.

noli's read

Dr. Matthew Walker, a renowned neuroscientist, provides nuance here regarding the common fear of hypersomnia. While observational data often show a U-shaped curve linking very long sleep durations to increased mortality, current research suggests that this is often a case of reverse causality: it is not the sleep that causes the illness, but rather underlying pathologies that drive an excessive need for sleep. Studies, such as those published in the Journal of the American Geriatrics Society, indicate that for healthy individuals, the body naturally regulates its needs. However, asserting that there are 'incredible benefits' to sleeping beyond the recommended norm remains an optimistic interpretation. There is no solid evidence to suggest that 'oversleeping' activates additional physiological benefits compared to adequate and regular sleep. The scientific consensus favors quality and regularity over mere prolonged quantity.

the sources

No named source held this one up — that absence is part of the verdict.