So my understanding is that schizophrenia occurs when there is high dopamine activity. On the other hand adhd occurs due to low dopamine activity.

So here's my question: if the probability of someone suffering of schizophrenia is p. And the probability of someone suffering from adhd is P. Then naively assuming exclusive events one would expect the probability of having both schizophrenia and adhd to be P times p. But maybe they can interact with each other the probability of suffering from both is different? (Can someone direct me to a study?)

  • $\begingroup$ The mechanisms of neither schizophrenia nor ADHD are fully understood, and it's certainly not possible to reduce either to "high or low (some specific neurotransmitter)", I'm not sure where you got that idea. $\endgroup$
    – Bryan Krause
    Commented Aug 26, 2023 at 18:41
  • $\begingroup$ I agree there are complexities. But I think the correlation with a specific neurotransmitter should tell me if it's possible to think of these of mutually exclusive events $\endgroup$ Commented Aug 26, 2023 at 18:46
  • $\begingroup$ Found it: ncbi.nlm.nih.gov/pmc/articles/PMC6412852/…. $\endgroup$ Commented Aug 26, 2023 at 18:50
  • $\begingroup$ I had seen an answer previously (or so I thought) ..did it get deleted? $\endgroup$ Commented Aug 27, 2023 at 16:42
  • $\begingroup$ Yes, there was, it was automatically generated spam. $\endgroup$
    – Bryan Krause
    Commented Aug 27, 2023 at 17:52

1 Answer 1


There needs to be a lot more changes in the brain than just high dopamine for someone to have schizophrenia. Many people would have elevated dopamine and not be schizophrenics. For example, impulsive and aggressive people have high dopamine but are not schizophrenics. Happy people have high dopamine too!


Moreover, high dopamine in schizophrenia is characterized by it being high in particular areas and particular cells, not the whole brain. Schizophrenia is also categorized by misconnected brain regions, cellular type imbalance (e/i ratio), misregulated synapses, and more! Dopamine alone is not enough to categorize schizophrenia or ADHD!


Because mental illnesses are poorly understood and share a lot of commonalities between them, psychiatrists often diagnose by symptoms and expertise as opposed to biological changes. We do not know enough biology (yet) to look at a brain and say schizophrenia or adhd; we look at a person's behavior and symptoms, etc.

DSM 5 is what psychiatrists use to diagnose: if you look at the section for schizophrenia or adhd, there is not much biology, just behavior.


It is not possible to calculate the probability of ADHD and schizophrenia from dopamine alone because dopamine misregulation in schizophrenia is region-specific and needs a lot more brain changes with it. Also, there is no accepted way of biologically differentiating schizophrenia or ADHD; it is only (right now) by the person's behavior and appearance etc.


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