Do sevens go lower in Shithead?
Verdict: not in the official rules, but it's the most popular house rule in the game. At shitheads.co.uk, the 7 is just a card, and the "go lower" power belongs to the 9. In many houses, especially across the UK, a 7 forces the next player to play 7 or lower. Neither table is lying to you. They just grew up differently.
The case for
Sevens-go-lower creates panic in the mid-game, punishes high-card hoarders and gives an otherwise dull card a personality. It's the rule most people mean when they say "we play with the proper rules".
The case against
Stacking the descent on the 7 as well as the 9 makes the game a constant downhill scramble, and the 7 already sits at the awkward middle of the deck. Giving the power to the 9 alone keeps the descent rarer and nastier: by the time a 9 lands legally, the pile is usually tall enough for it to hurt.
Our ruling
Nines carry the descent. Sevens carry nothing but their own quiet dignity. If your table disagrees, call it a house rule and go in peace.