did psychiatry work backwards from its drugs?

in most of medicine the order is: find what is broken, then build something to fix it. in psychiatry the two most famous theories ran the other way. a drug did something, and the theory of the illness was built from what the drug did. this page shows that order in the researchers’ own words, then shows what the later evidence found, which is more interesting than either side’s slogan.

read this first if you take one of these drugs. nothing here says your illness is not real or that your medication does not help you. whether a theory is right and whether a drug works for you are two different questions. this page is about the first one. it is not a reason to start, stop or change anything; that conversation belongs with your prescriber.

the dopamine theory came from the drugs

the first antipsychotic reached psychiatric wards in 1952 (the story is on our how the drug was found page). nobody knew how it worked. the theory of schizophrenia that still frames the field was built afterwards, from the drugs. in the words of a 2009 review by two of the field’s leading dopamine researchers, the first version of the dopamine hypothesis “emerged from the discovery of antipsychotic drugs,” and “it was not until the 1970s, however, that the dopamine hypothesis was finally crystallized with the finding that the clinical effectiveness of antipsychotic drugs was directly related to their affinity for dopamine receptors.”^[1]

read the logic in that sentence. the drugs calmed psychosis; the drugs blocked dopamine receptors; so psychosis must be too much dopamine at those receptors. that is reasoning from the treatment back to the disease. it is not illegitimate, and it has produced real findings, but it is the opposite of how cardiology or oncology usually works.

and the drugs never left that receptor. the 2009 review: “at clinical doses all currently licensed antipsychotic drugs block striatal D2 receptors.”^[1] a 2012 meta-analysis from the same group opens with the sentence this page is named for: “despite 5 decades of drug discovery, all of the treatments rely on the same mechanism: dopamine D(2) receptor blockade.”^[2]

then they measured, and the problem was somewhere else

once brain imaging could look at dopamine in living patients, researchers could test the theory instead of inferring it. the 2012 meta-analysis pooled 44 imaging studies, 618 patients and 606 controls. it found “a highly significant elevation … in presynaptic dopaminergic function in schizophrenia with a large effect size (Cohen d=0.79).” the receptors the drugs block showed only a small elevation, “not evident in drug-naive patients.”^[2]

so the theory was partly right: dopamine is involved, and strongly. but the largest abnormality is upstream, in how much dopamine is made and released, not at the receptor the drugs were designed around. the authors say it plainly: “current drug treatments, which primarily act at D(2/3) receptors, fail to target these abnormalities,” and the 2009 review: “current treatments are acting downstream of the critical neurotransmitter abnormality.”^[1][2]

the serotonin theory: the same order

a link between low serotonin and depression “was first suggested in the 1960s,” after the first antidepressants had already been found. a 2022 umbrella review names the working-backwards step directly: “it is often assumed that the effects of antidepressants demonstrate that depression must be at least partially caused by a brain-based chemical abnormality.”^[3] it then reviewed 17 systematic reviews, meta-analyses and large studies, and concluded that “the main areas of serotonin research provide no consistent evidence of there being an association between serotonin and depression.”^[3]

that review has critics, and they are not fringe. thirty-five researchers replied in the same journal that its conclusion is “overstated,” citing “methodological weaknesses,” “selective reporting of data” and errors in reading the tryptophan-depletion and imaging studies.^[4] both sides declared interests: one author of the review co-founded a company that helps people stop antidepressants; authors of the reply have received industry honoraria. we print both and take neither side’s word for the other.^[3][4]

the strongest case the other way

• schizophrenia “has a heritability of 60-80%.” a 2022 study of 76,755 people with schizophrenia and 243,649 without found 287 distinct genetic loci, concentrated in genes expressed in neurons.^[5] there is biology here. it was found decades after the drugs and it does not point at one receptor.
• the imaging finding above is itself a real, large, replicated abnormality.^[2] “working backwards” describes where the theory started, not a claim that nothing is there.
• a drug can work without its theory being right. antidepressants beat placebo across 522 trials and 116,477 people.^[7] whether they work, and how much, is a separate question from why.
• “few,” not “none”: a 2012 paper co-written by the director of the national institute of mental health says patients “show many biological abnormalities,” but “few of these have led to tests with clinical utility.”^[6] the gap is between findings and tests.

what it adds up to

three things hold at once. psychiatric illness has biology, and the genetics and imaging keep finding more of it. the two theories most people were taught were fitted to drug effects rather than discovered in patients, and one has not held up well. and the drugs are still built around the old target, which is part of why, after fifty years, the new antipsychotics mostly differ in side effects rather than in how they work.^[2]

if a field reasons from its drugs to its diseases, the next drug tends to look like the last one. the upstream findings are where the authors of the imaging work say new treatments should aim.^[1][2] until then, no major psychiatric diagnosis has a lab test,^[8] and a theory you heard in a clinic is worth asking about.

questions people ask

sources

1. Howes OD, Kapur S. The dopamine hypothesis of schizophrenia: version III, the final common pathway. Schizophrenia Bulletin 2009;35(3):549-562. PMC2669582. Read in full text 2026-09-29. Version I “emerged from the discovery of antipsychotic drugs”; “It was not until the 1970s, however, that the dopamine hypothesis was finally crystallized with the finding that the clinical effectiveness of antipsychotic drugs was directly related to their affinity for dopamine receptors” (citing Seeman et al., Nature 1976, and Creese et al., Science 1976); “at clinical doses all currently licensed antipsychotic drugs block striatal D2 receptors”; “Current treatments are acting downstream of the critical neurotransmitter abnormality.” https://pmc.ncbi.nlm.nih.gov/articles/PMC2669582/
2. Howes OD, Kambeitz J, Kim E, et al. The nature of dopamine dysfunction in schizophrenia and what this means for treatment. Archives of General Psychiatry 2012;69(8):776-786. Meta-analysis of 44 PET and SPECT studies, 618 patients and 606 controls. “despite 5 decades of drug discovery, all of the treatments rely on the same mechanism: dopamine D(2) receptor blockade”; “a highly significant elevation (P<.001) in presynaptic dopaminergic function in schizophrenia with a large effect size (Cohen d=0.79)”; “There was no evidence of alterations in dopamine transporter availability”; a small D2/3 elevation (d=0.26) “was not evident in drug-naive patients”; “Current drug treatments, which primarily act at D(2/3) receptors, fail to target these abnormalities.” PMID 22474070, PMC3730746. https://pubmed.ncbi.nlm.nih.gov/22474070/
3. Moncrieff J, Cooper RE, Stockmann T, Amendola S, Hengartner MP, Horowitz MA. The serotonin theory of depression: a systematic umbrella review of the evidence. Molecular Psychiatry 2023;28(8):3243-3256 (online 20 July 2022). PMC10618090. Read in full text 2026-09-29. Introduction: “A link between lowered serotonin and depression was first suggested in the 1960s”; “It is often assumed that the effects of antidepressants demonstrate that depression must be at least partially caused by a brain-based chemical abnormality.” 17 studies included. Conclusion: “The main areas of serotonin research provide no consistent evidence of there being an association between serotonin and depression, and no support for the hypothesis that depression is caused by lowered serotonin activity or concentrations.” Declared interests include one author co-founding, in April 2022, a company aiming to help people stop antidepressants. https://pmc.ncbi.nlm.nih.gov/articles/PMC10618090/
4. Jauhar S, Arnone D, Baldwin DS, et al. (35 authors). A leaky umbrella has little value: evidence clearly indicates the serotonin system is implicated in depression. Molecular Psychiatry 2023;28(8):3149-3152. The umbrella review’s conclusion is “overstated”, citing “methodological weaknesses in the review process, selective reporting of data, over-simplification, and errors in the interpretation of neuropsychopharmacological findings”, with tryptophan depletion and serotonergic molecular imaging as the examples. Declared interests include industry honoraria for educational talks on antipsychotics. PMID 37322065. https://pubmed.ncbi.nlm.nih.gov/37322065/
5. Trubetskoy V, Pardiñas AF, Qi T, et al. Mapping genomic loci implicates genes and synaptic biology in schizophrenia. Nature 2022;604:502-508. “Schizophrenia has a heritability of 60-80%”; a genome-wide study “of up to 76,755 individuals with schizophrenia and 243,649 control individuals” reports “common variant associations at 287 distinct genomic loci”, concentrated in genes expressed in neurons. PMID 35396580. https://pubmed.ncbi.nlm.nih.gov/35396580/
6. Kapur S, Phillips AG, Insel TR. Why has it taken so long for biological psychiatry to develop clinical tests and what to do about it? Molecular Psychiatry 2012;17(12):1174-1179. From the abstract: “Patients with mental disorders show many biological abnormalities which distinguish them from normal volunteers; however, few of these have led to tests with clinical utility.” PMID 22869033. https://pubmed.ncbi.nlm.nih.gov/22869033/
7. Cipriani A, Furukawa TA, Salanti G, et al. Comparative efficacy and acceptability of 21 antidepressant drugs for the acute treatment of adults with major depressive disorder. Lancet 2018;391:1357-1366. 522 trials, 116,477 participants: “All antidepressants were more effective than placebo.” Cited for the other direction: a drug can outperform placebo whether or not the theory attached to it is right. https://doi.org/10.1016/S0140-6736(17)32802-7
8. The DSM, on this site: no DSM diagnosis of a major mental disorder is confirmable by a laboratory test, with the NIMH director’s 2013 statement and its limits. https://www.veisund.com/topics/the-dsm

related: the DSM: why no diagnosis in it has a lab test · how each drug was found

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