When I wake up at 4am and my brain instantly starts non-stop looping and branching across all sorts of thoughts and topics, most of which have nothing to do with work, then no - ADHD isn’t just a problem with my work environment. My work environment may exacerbate it - absolutely. But that’s a contributing factor not a cause.
For me, my ADHD (formally diagnosed ADHD & ASD at age 58; finally my life made sense) manifests as an inability to slow down my thoughts, especially the constant context switching. I can only achieve it doing certain contemplative activities eg. intense workout at the gym, laying on my Shakti mat, meditating with breathwork.