Dark circles, unlike most beauty woes (fine lines, not-so-fine wrinkles, pervasive sagginess), aren't directly linked to ageing. It's perfectly possible to find someone in the full flush of youth with shadows beneath their lower lids.
Previously, I thought there was something pretty glamorous about a dark circle or – more likely – two. But that's probably due to a teenage literary diet of Jilly Cooper novels, where the foxier characters have "bruised, scabious-blue eyes" like "Botticelli angels who'd had too much nectar at lunchtime".
Unhappily, when those perky cherubic features disappear, dark circles rapidly begin to look less like the indicator of a white night of high jinks than the fact that you're well and truly knackered.
The bad news is that they're partly hereditary. More encouraging is that you'll improve matters by attending to your general health – less nectar at lunchtime, sorry – and using a good, brightening eye cream.