The title invokes a phrase of the great German-Jewish Frankfurt School psychiatrist Erich Fromm. Having fled Germany during the Nazi ascendancy for the United States, Fromm dissected the psychosocial conditions that had fostered Nazism and the tactics that individuals and cultures used to evade the burden of freedom. A decade after the war, his book The Sane Society (1955) further explored the idea of collective insanity, addressing a challenge thrown down earlier by Sigmund Freud. In Civilization and its Discontents (1930), Freud had asked if psychoanalytic theory did not indicate that civilisations or epochs, even the whole human species, might be suffering from deep and old neuroses. At this level, there was and could be no control to indicate, even theoretically, what the absence of neurosis might look like.

The Sane Society took up what Freud could or would not, mapping the contours of a society that meets human needs not as they are felt but ‘objectively, as they can be ascertained by the study of man’. Multitudes could arrive at deranged ideas; just as there is a ‘folie à deu’, wrote Fromm, there is a ‘folie à millions’, a collective psychosis. It is a stance adopted by critics of ‘nuclear madness’ and experimented with more recently in The Great Derangement (2016) by Amitav Ghosh. The idea contravened the relativism already prominent in the postwar years, pointing to a set of ‘universal criteria for mental health’, which obtained across all humanity, and an underlying ‘normative humanism’. The project, for Fromm, was to ‘ascertain what is the nature of man, and what are the needs which stem from this nature’.

But how? Beyond these theoretical explorations, any progress towards universal mental health criteria would require a common psychiatric vocabulary. But as Erwin Stengel, who had also fled Nazism (from Vienna to London), argued, the twenty-eight competing classification systems in use by the 1950s showed serious discrepancies in psychiatric diagnoses. Researchers at the US National Institute of Mental Health and the Maudsley Hospital in London therefore began a study of the differential in diagnoses of schizophrenia and depression. After watching a series of videotaped interviews and to make diagnoses, London psychiatrists proved twice as likely to diagnose the same patients with depression as their counterparts in New York, who were twice as likely to diagnose schizophrenia. London and New York were hardly worlds apart culturally – what of Taipei and Buenos Aires?

Stengel suggested that this chaos might be corrected by the careful analysis of diagnostic surveys. Mad by the Millions is the history of the quest for a standard international classification of mental disorders through such surveys, seminars, and videography, which produced data for the questions and contentions of Freud and Fromm. The roots of this bureaucratic exercise lay deep in the despair and hope of the postwar years; it was a means of establishing the human universalism, or world citizenship, seen as the only hope of insuring against the return of the violence of what Eric Hobsbawm would modestly call the ‘age of extremes’. Global peace was to be underpinned partly by the pursuit of global health, as well as by scientific evidence of universal human nature.

Thirty years of violence and despair had elicited a new joint venture between psychiatry and social science. Social psychiatry focused on the social and cultural determinants of mental illness: poverty, inequality, social conflict. Its proponents – including Fromm – saw individual cases of mental illness in diseased cultural configurations or toxic social environments, and melded psychiatric knowledge with public health. They preferred prevention to treatment, seeking controls that would produce saner, better-balanced societies.

Epidemiological reasoning facilitated these aims and, for WHO administrators looking to promote world mental health, was a necessary step in determining priorities. Psychiatric diagnoses had always been fraught, and while a comparative epidemiological exercise threatened to further expose the profession to the critiques of anthropologists and sociologists, psychiatry offered a glimpse of salvation. The field’s evidentiary problems might be solved by the light epidemiological findings would shine on the aetiology of mental disorders.

Wu shows how the idealism of the immediate postwar years quickly dwindled in the face of Cold War geopolitics and other kinds of political, economic, and biographical realities. In its execution, the ISPP was less a product of psychiatric dreamscapes of modernity, or a trading zone in which partners exchanged expertise and knowledge according to their relative competitive advantages, than an exercise in original equipment manufacturing, in which a company arranges to have patented designs built offshore. Far from imperialistic in its first impulse, the ISPP acquired a functional imperialism (even in places drawing on colonial datasets and classifications), primarily for pragmatic and budgetary reasons. The project’s democratic ambitions were sacrificed, Wu argues, to the desire for a world standard for mental disorders – to the vision of human universalism.

Committed as they were to the idea of human universalism – to the possibility of a scaled-up sane society – psychiatrists at the WHO sought to understand the roots of diagnostic variation between cultures. A fascinating page is devoted to back-trans-lations of a diagnostic question about the automaton. For Fromm, an automaton was one who ‘never experiences anything which is really his; who experiences himself entirely as the person he thinks he is supposed to be’, but other languages threw up a wealth of adjacent figures: marionette, fairy, zombie, doll. Wu shows how, for all the investment in standardisation, and for all the technologies applied to neutral description and the analysis of enormous amounts of data, the ISPP invariably produced evidence of the deep imbrication of culture, language, and mental disorder.

The epilogue tells how the 1980 publication of the third revision of the rival US diagnostic system – DSM-III – signalled the ascendancy of biological psychiatry and pharmaceutical solutions. Carried in their wake was a profound psychiatric individualism that ran counter to the ambitions of social psychiatry. Mad by the Millions is therefore a fascinating study of the faltering of these psychiatric dreams in their encounter with the exigencies of international organisation and the gamut of human experience.