I don't know how accurate it is, but in a few places I've seen a graphic showing brain scans of various mental/neurological conditions, including PTSD and ADHD and at least two others. (For example, in ADHD brain scans show how the brain literally shuts down in the frontal cortex when the individual tries to concentrate. For PTSD they show how the brain activates in various regions during a flashback episode.) Could probably find it if I did some digging.
I think psych meds and stuff have their place, but there's still a lot we don't know about how mental illness works and so meds don't all work the same for everyone. I've known a few people who say their mental health providers did a blood panel on them to determine if certain psych meds would work for them, apparently they can actually determine that by some test. Some people's bodies are resistant to the drugs on the market.
Me, I take a couple psych meds, haven't had a dosage change in like a year or two. I guess they work well enough. I've started seeing a counselor again due to my mild to moderate work anxiety.