Madhouse is noted for its specific aesthetic choices that defined horror in the mid-2000s:

The basement is characterized by dark, gritty visuals and "stomach-turning" practical effects, creating a sense of claustrophobia and impending doom.

Reviewers highlight the "Argento-esque" nature of the kills, particularly a cringeworthy electrocution scene that remains a standout for practical effects fans.

Through its final twist, Madhouse examines how past trauma can fracture a personality, leading to a literal and figurative "house divided".

The film employs "herky-jerky" ghostly figures and frantic editing, a style popular following the success of The Ring (2002).