It’s Urban Fantasy, and as non-magical people in the book are exposed to the magic they may feel reality is unhinged & unstable and deal with it in varying degrees including not well at all. But for us as the reader, none of it is a shock since we’re privy to the characters with magical powers and know things aren’t as they appear.
There’s no descriptions of them being in the throes of addiction, or in withdrawals etc. Near the end of the book, you find out that someone is secretly a morphine addict.
She planned it and it’s a positive experience for her. No detailed description, just mentioned that it was her first time / she didn’t know what she was doing, but enjoyed it nonetheless.