Amid the vicissitudes of the COVID-pandemic, another disease quietly spread through the American population: depression. A staggering 1 in 3 adults in the United States are now suffering from the affliction, a rapid elevation that shows no sign of reversal. Depression is a uniquely debilitating illness. While perhaps most readily thought of as an intense sadness, a depressive episode touches all of life. It often interferes with basic behaviors like eating and sleeping, drains patients of their energy and interest in daily life, clouds thinking, and puts up barriers to relationships. This intense and isolating experience—which often remains hidden—can even drive some of those who suffer it to take their own lives.
Faced with the scale and severity of this human crisis, scientists have rightly directed tremendous efforts to understanding the biological basis of depression. But the further this research has progressed, the clearer it has become that reductionism is a dead end. Depression is not merely biological, and efforts that ignore this fact are inefficient at best and illusory at worst; to end this crisis, we will need a better account of the human person, a fuller picture of what it means to lead a flourishing life.
The Thomistic view of the human person is such an account. Though long side-lined in clinical and theoretical psychology, the Catholic intellectual tradition is uniquely able to account for the nature of depression and to animate the journey to healing.
The Neuroscientific Study of Depression
The current approach to depression in scientific research is strongly reductionist. This was not always the case: the study of mental illness was once strongly rooted in descriptive accounts of the subjective experience of patients. But after decades of failure to translate findings from research into effective treatments in clinical practice, the field decided to narrow its gaze. From now on, neuroscientists Thomas Insel and Remi Quirion proclaimed in 2005, “mental disorders [should] be understood and treated as brain disorders.” Depression should be seen as a biological state, the result of—and perhaps nothing other than—aberrant neural structure and function.
At the time, Insel was the head of the National Institute of Mental Health, which funds a great proportion of psychiatric research throughout the world. Insel was therefore able to enact his reductionist manifesto from the top down. In 2009, the NIMH introduced a new framework to guide the allocation of research funding, encouraging scientists to seek to “identify molecular or neural mechanisms . . . rather than creating models of [mental] diseases.”
The field listened. In the years that followed, neuroscientists discovered a vast range of biological differences present in depressed patients. These include inherited differences in various genes, including those that regulate brain growth; altered levels of some neurotransmitters, the chemical messengers of the brain; disorganization of hormonal systems, such as an excessive response to stress; and changes in the nervous system, including a slowdown in the birth of new neurons.
But a coherent biological account of depression remains elusive. In the first place, it is not clear which of the observed changes precede the onset of depression, and even then, whether they are causal or merely correlative. Complicating the picture, not all the changes associated with depression are present in every patient, which is inconsistent with the view of depression as a single physical phenomenon or condition. Furthermore, when scientists trigger these neurobiological changes in animals like mice or monkeys, the animals do not always develop symptoms of depression. Thus, as the field itself acknowledges, “it is not clear whether many of these biological factors cause depression, or whether they are actually biological consequences of the condition.”
Nevertheless, psychiatric efforts to heal depressed patients usually begin on the level of biology, typically through prescribing a medication that changes levels of neurotransmitters. Most of these antidepressants fail to perform better than a placebo—a harmless sham treatment like a sugar pill.
The few that are successful tend to work in a small subset of patients, and even in those cases, their mechanism of action in the brain remains enigmatic. While some newer experimental methods are showing promise, most neural differences in depression are untreated or unsuccessfully treated. In the bleak assessment of eminent psychiatrist Allen Frances, while the search for the neurobiology of mental illness may have been “an exciting intellectual adventure . . . it hasn’t helped a single patient.”
Moving Beyond Reductionism
Psychiatrists and physicians have the task of healing persons. So if researchers are to facilitate their work, they too should acknowledge that depression afflicts persons, not merely their nervous systems.
What would it look like for modern scientific research to move beyond the narrow limits of biological reductionism? This would entail a change in methodology. Perhaps it could draw on complexity science, which can accommodate non-linear interactions and multiple levels of explanation. Or, perhaps it would prioritize the triangulation of findings with diverse approaches and theories? But whatever methodological adjustments are made, such a science would also require a stronger foundation, a better understanding of the human person. In other words, the field needs a working anthropology that is more robust and reasonable than a reduction to biology.
The shadow of such an anthropology already lurks in scientific and clinical observations of depression. The first evidence is the simple fact of subjectivity. Empirical measures are not enough to establish the presence of depression, which takes place in the interior experience of the patient and which he or she must freely choose to understand and share with others. The most successful treatments for depression, such as Cognitive Behavioral Therapy, work by purifying this internal experience of what is disordered and aligning thoughts and beliefs with the truth of reality.
A second indicator is the inherently relational nature of the human person. Time and again, studies point to enduring and secure relationships as strong sources of protection against depression. Loneliness and social difficulties, on the other hand, are powerful risk factors for depressive episodes—which can in turn impair social abilities and alienate one from others.
A third element is spirituality. While a sense of meaninglessness can fuel the onset of depression, religious experiences and beliefs demonstrably accelerate recovery and protect against the risk of developing depression in the first place.
Of course, as the human mind and soul are not a “ghost in the machine” but embodied realities, these facts do not negate the relevance of the brain. But they do identify the higher levels of the human person as being inescapable aspects of depression.
As scientific researchers seek to move beyond a reductionist view of depression, they would do well to turn back to the authority of philosophical and religious traditions, which contain a wealth of rich anthropological insights. Among them, the Thomistic tradition is set apart by its internal coherence and expanse. Its view of the human being as a composite of a body and rational soul, which possesses the powers of intellect and will, offers a fruitful ground for a non-reductive consideration of depression.
The Thomistic Account of the Human Person
Nowhere is the expanse of this anthropology clearer than in the magnum opus of St. Thomas Aquinas, the Summa Theologiae. Through this work, he systematically explains Catholic teaching, and his account of the human person as a body-soul composite lays the groundwork for much of his explanation.
The distinction between what falls under the “body” and what falls under the “soul” is not as straightforward as one might think. The body is, in short, what neuroscience and medicine can address; this includes sensory input, sensory understanding, and emotions. It includes the aspects of the person that we share with other living things. For example, dogs can experience and understand sensations, and, as anyone who has observed a dog can tell you, they clearly have emotions—though those emotions may differ in nature from our own.
The body is concerned with physical and emotional interactions with the surrounding world, and therefore primarily, in the view of Aquinas, with beauty. Without the sensory input and understanding that are concomitants of our corporeality, we would be incapable of experiencing the beauty of creation or of feeling the emotional responses that accompany these experiences.
For a body to be a human body, however, it must be animated by a soul that is spiritual. Aquinas explains the spirituality of the human soul in terms of the intellect and the will. The intellect accounts for our ability to create abstract ideas from our sensory experience and to achieve rational—rather than merely sensory—understanding. It also makes it possible for us to discuss, analyze, set goals, and plan on the basis of that abstract thinking and rational understanding. The will, for its part, accounts for our desires and our ability to freely act on what the intellect knows and understands. In short, while the body deals with beauty, the intellect deals with truth, and the will deals with goodness.
The Intellect and the Will in Depression
Reductionist research has exclusively focused on the manifestation of depression in the body. But what might occur in the spiritual soul in the circumstance of depression? A closer examination of the nature of the intellect and will can shed light on this question.
As we have seen, Aquinas relates the intellect to the rational nature of the human person, by which he or she “advances from one understood thing to another” (ST I, q.79, a.2). The intellect can therefore guide our desires for and inclination toward things; it can inform the will. The will itself has no role in judging what is good, but rather is inclined toward an “end that is a good or an apparent good” as judged by the intellect.
The will can then be resolved further into what Aquinas calls the “immediate act” and the “act commanded.” The immediate act is the desire to act in a certain way toward a certain end or goal, while the act commanded is the interaction of the will with what is exterior to the person, putting the immediate act into execution. When the will is thwarted or incapacitated in some way (“suffers violence”, in Aquinas’s terminology) it is the “act commanded” that is affected, preventing the outward act that puts into effect the “immediate act.”
The immediate act cannot “suffer violence,” as it arises naturally from the influence of the intellect. Therefore, a flaw in the immediate act—an incorrect desire—points to a flaw in the intellect, whereas a flaw in the act commanded—the actual deed—reflects a flaw in the will (ST II-I, q. 8, a. 1). A consideration of two of the behavioral symptoms of clinical depression illustrates that it involves an attack on these powers of the spiritual soul.
One of the most recognizable symptoms of depression is anhedonia, or the loss of enjoyment in previously enjoyable tasks. We would argue that this is a manifestation of a flaw in the will, specifically in the act commanded. Anhedonia does not mean that the person does not want to perform the task; rather, it means that they are incapable of experiencing the previous pleasure that the task brought about, and consequently lack the motivation to perform it. This indicates that the immediate act (the desire) is untouched, while the act commanded (the capacity to perform the action) is under attack. This behavior is a demonstration of the type of “violence” against the will that Aquinas in the Summa says is possible (ST II-I, q. 6, a. 4).
Another clinical symptom of depression can be suicidal ideation. This symptom arises as a violence to the intellect. It is a philosophical axiom that it is always better to exist than not to exist. For this reason, suicide cannot be a good, as its goal is non-existence. Because the will always tends toward a good or apparent good, suicidal ideation must be a result of a flaw in the intellect, which leads the will to perceive this objective evil as an apparent good.
If depression is not only a bodily ailment, what kind of attack might it inflict on the soul? We argue that depression acts similarly to how Aquinas describes despair in the Summa and that recovery from depression therefore requires the cultivation of hope.
Despair and Hope
Aquinas describes despair as a type of desire. Namely, it is a desire for something that is inherently difficult to attain, accompanied by the belief that attaining it must be impossible (ST I-II, q. 40, a. 1). Despair can arise in numerous ways, such as past experiences of fruitless desires. This can easily be compared to one of the primary theories of depression: learned helplessness.
In this model, tested primarily with rats, the animal is consistently prevented from escaping an unpleasant stimulus, such as pain or fear. Eventually, these animals stop trying to escape, even once conditions are changed to make an escape easily available. Learned helplessness also occurs in human experiences of depression, where it contributes to the perpetuation of the affliction by favoring withdrawal and passivity.
Conversely, the path to human flourishing is fed by hope. Aquinas states that hope, though not the same thing as desire, is also a specific type of desire (ST I-II, q. 40, a. 1). It is a desire for something that is inherently difficult, but nonetheless believed to be possible. Here, it is important to note that Aquinas discusses hope in two senses: as an emotion and as a virtue.
Hope as a mere emotion is the generic desire, held in the intellect, for something difficult but possible. For hope to be raised to a virtue, the principal object of that desire must be eternal happiness (ST II-II, q. 17, a. 2). When it is eternal happiness that we see as difficult to obtain, but still possible, and we direct our lives toward that desire, hope becomes a virtue held in the will (ST II-II, q. 18, a. 1).
The journey of recovery from depression is often cyclical, with seasons of relapse and acute suffering. Only certainty of the possibility of an experience of the goodness of life—whether during life on earth or for eternity as well—can sustain the soul on this path. As such, the cultivation of hope in the intellect and will is a critical aid to psychological health—a fact discernable even on the level of epidemiology.
How might a person grow in hope? In Aquinas’s view, hope as a theological virtue surpasses human nature: its object is God, and it is infused in the soul by God alone (ST II-II, q. 62, a. 1). However, human agency remains, for this gift must be embraced in freedom if it is to bear fruit. Furthermore, as God acts through secondary causes, the cultivation of hope in a soul can take place through the implicit experiences of receiving the love of a community and acting in accordance with its end (1 John 3:21–23).
The Path Ahead
The Thomistic view of the human person can inform scientific research on depression in numerous ways.
One starting point would be to build on existing psychological traditions and therapies that resist reductionism. One example is Cognitive Behavioral Therapy (CBT), one of the most effective treatments for depression. CBT works to realign thoughts and behaviors with the truth and goodness of reality.
For instance, CBT may help patients un-learn learned helplessness by teaching them to try to reach the good, even though their attempts may have been fruitless in the past. In Thomistic terms, CBT takes into account how the intellect directs the will, and specifically, the act commanded. Because it educates the soul in this way, CBT can lead patients back from despair to hope. Integration with research on the body would be a promising step toward an integrated understanding of depression.
Another fruitful starting point for scientific research would be to develop new therapies through interdisciplinary collaborations with philosophers or theologians—perhaps especially those formed in Thomistic thought. The groundwork for such an endeavor has been laid by scholars at Divine Mercy University, who recently published a comprehensive framework for mental health care rooted in philosophy and Catholic theology.
Yet another could be a phenomenological approach that begins in listening to the lived reality of those who are experiencing depression. Indeed, patients already report close interpersonal relationships and spiritual and religious experiences to be critical factors in their mental health. While this comes as no surprise to one who knows the origins of the virtue of hope, researchers would be wise to attend to these data.
Regardless of the specific point of departure, research on depression must consider the whole person, and not just the body. While a reductionist approach to mental health follows logically from the leading contemporary anthropology, its failure to effectively understand and treat depression is undeniable and comes at a devastating human cost.
Research into the biology of mental illness certainly has the potential to contribute insights that advance human flourishing. But only by entering into dialogue with a more robust working anthropology can this potential become a reality for vast number of people suffering the scourge of depression.
EDITORIAL NOTE: This article is part of a collaboration with the Society of Catholic Scientists (click here to read about becoming a member). A version of this article with foonotes is available here.