The journal Behavioral and Brain Sciences features several prominent researchers in its latest issue debunking the notion that mental health concerns are “brain disorders.” It begins with a paper by researchers in the Netherlands arguing that neurobiology will never convincingly explain any mental health concerns. The rest of the issue includes dozens of commentaries by influential researchers, some supporting the initial premise, and others attempting to argue against it. In response, the initial study authors point out that none of the responses can provide any convincing evidence that neurobiological reductionism has succeeded in a meaningful way.
The lead article and response to the commentaries were written by Denny Borsboom at the University of Amsterdam, Angélique Cramer at Tilburg University, and Annemarie Kalis, at Utrecht University, all in the Netherlands.
“None of the commentators appears able to point to convincing evidence that, generically speaking, mental disorders are brain disorders,” they write, “in fact, it seems that most commentators do not even bother. This brings us to the first important conclusion of this response to commentaries: The thesis that mental disorders are brain disorders enjoys no appreciable support.”
The researchers present a thought experiment that ably delineates just how poorly the idea of brain disorders has fared: Imagine a world in which biological reductionism had succeeded. The neurobiology of mental disorders is understood, and treatments are tailored to that biology and have a high success rate. And now imagine that in this world researchers write a peer-reviewed article in a high-profile journal arguing that brain disorders do not exist.
In that world, we can only imagine that researchers would muster piles of scientific evidence to show that brain changes are responsible for mental health concerns. Every commentary would simply point to numerous studies demonstrating that point. There would be no debate. Instead, in response to this argument, no commentator is able to point to such evidence, and “most do not even bother” to try to produce such evidence.
“The reductionist position on mental disorders as brain disorders does not represent a scientifically justified conclusion, as is often supposed in the popular and scientific literatures, but instead is a hypothesis.”
Borsboom and colleagues argue, in a high-profile journal, that the hypothesis of biological reductionism does not sufficiently explain the human experience. Instead, a variety of other explanations work just as well, if not better.
Borsboom and his co-authors suggest that psychiatry should focus on intentionality—the meaning of experiences—as it is the unique defining feature of all human explanation of mental and emotional problems. Focusing on neurobiology has been, according to the researchers, a failure, which ignores the phenomenological aspects of the human experience and, thus, essentially misses the point of mental health concerns.
According to Borsboom, Cramer, and Kalis:
“It is highly unlikely that the symptomatology associated with psychopathology can ever be conclusively explained in terms of neurobiology. Therefore, sticking to the idea that mental disorders are brain disorders may be counterproductive and can lead to a myopic research program.”
The researchers argue that simple explanations are never going to be found to reduce mental states to biological differences, for several reasons. Mental health diagnoses are based on clusters of “symptoms,” which are culture-bound and change over time (as with each new edition of the DSM, the “bible” of psychiatry) which makes it impossible to assume that we would find a biological correlate to an arbitrary list of very different symptoms. For instance, depression may include weight gain, weight loss, insomnia, fatigue, oversleeping, as well as a number of emotional states that may or may not be present. To assume that all these contradictory features could be due to the same biological substrates is flawed.
Additionally, because correlation cannot prove causation, it is just as likely that any neurobiological changes detected are the result of a mental state, rather than the cause. That is, changes in a person’s neurotransmitter levels would actually be expected after drastic changes in sleep, eating, and mood states—biological changes could be caused by routine changes such as this, or they could both be part of some other process.
Further, the researchers argue that identifying the “symptoms” of psychiatric diagnoses requires attention to the environmental context and the person’s experience. That is, symptoms are described in the DSM using contextual, experiential language, rather than objective language. For instance, the criteria for depression “feelings of excessive or inappropriate guilt” requires the clinician to contextually examine the source of guilt and decide whether it is inappropriate given the content of the guilty feelings.
Influential Stanford scientist John Ioannidis wrote one of the commentaries published with this article. Ioannidis discusses how research on mental health concerns should proceed, given what he calls the “dead end” of the neurobiological research agenda.
He suggests that mental health interventions should focus on environmental changes, rather than the neurobiological correlates of mental health. That is, the context of a person’s life has much more impact on their mental health than does their neurobiology. According to Ioannidis:
“Our societies may need to consider more seriously the potential impact on mental health outcomes when making labor, education, financial and other social/political decisions at the workplace, state, country, and global levels.”
Borsboom and his co-authors go even farther:
“In the current scheme of things, explanatory reductionism is a remote possibility, not a realistic research target. We do not have biomarkers that are sufficiently reliable and predictive for diagnostic use. We have not identified genes that are specific to disorders and explain an appreciable amount of variance. We have not obtained insight into pathogenetic pathways in the brain that are sufficiently secure to inform treatment. If anything, we should wonder why the massive investments in research, that should have uncovered these factors, have not pushed back the prevalence of common mental disorders by a single percentage point.”
They write that the reductionistic biological explanations of mental health “should not be understood as science but as science fiction.”
Borsboom, D., Cramer, A. O. J., Kalis, A. (2019) Brain disorders? Not really: Why network structures block reductionism in psychopathology research. Behavioral and Brain Sciences, 42(e2), 1–11. doi:10.1017/ S0140525X17002266
Ioannidis, J. P. A. (2019). Therapy and prevention for mental health: What if mental diseases are mostly not brain disorders? Behavioral and Brain Sciences, 42(e13), 23-24. doi:10.1017/S0140525X1800105X
Borsboom, D., Cramer, A. O. J., Kalis, A. (2019) Author’s response: Reductionism in retreat. Behavioral and Brain Sciences, 42(e32), 44–63. doi:10.1017/S0140525X18002091.