ADHD involves physiological differences in the prefrontal cortex that impact how dopamine signaling operates, among other things, which leads to the psychological symptoms. Saying “everyone is a little ADHD” is incredibly inaccurate and it’s frequently used as a form of ablism. It’s not a spectrum in that way. It’s like saying “everyone is a bit schizophrenic” to someone who feels compelled to do things by perceived “demons” in their brain.
Yes, some mental illnesses are common to all humans, like MDD but some, like ADHD and ASD result from physiological differences when compared to neurotypical brains.
All “abnormal psychology” has differing physiological differences when compared to a “neurotypical” brain. Those definitions are super shakey though. Neurotypical, as you say, is a super fuzzy definition and has really changed drastically in modern history.
And there are a shitload of people “a little bit schizophrenic”. You wouldn’t be able to tell though because the intensity, frequency, or persistence is not severe enough to affect thier life in an overwhelming manor. They have jobs, relationships, and can function in society.
Some people are a little bit “whatever” with different mental disorders. Believing mental health issues are binary, either they have a “disorder” or are healthy is no longer part of modern abnormal phycology. They are now thought of as spectrums where people can fall onto that spectrum in very very different severities. That is why people use the word spectrum.
