While modern films like Requiem for a Dream use stylized editing to show the "high," The Panic in Needle Park uses stillness to show the "low." It is a time capsule of a decaying New York City and a masterclass in naturalistic acting. It doesn't judge its characters; it simply observes them as they disappear into their own veins. To help you get more out of this topic, I can:

Helen doesn't start as an addict; she falls into it to stay close to Bobby.

The film famously lacks a soundtrack, relying on the abrasive sounds of New York traffic and sirens.