A short paper I wrote for a class on clinical psychopathology.
Mental health has long been considered as a separate entity from mental illness. Indeed, in many ways the field of psychopathology seems built on the assumption that “normal” behaviors are discontinuous with “abnormal” ones – and that the line dividing them acts as a strict and impenetrable barrier. But failures to capture the nuances of mental disorder in clinical practice have awakened resistance to this assumption. We have instead begun to wonder, as developmental psychopathologist Dante Cicchetti (1993) proposed, whether “the mechanisms responsible for abnormal behavior may be only quantitatively, not qualitatively, different from those that cause normal variability.”
So far, we have conducted little systematic research testing the hypothesis that abnormality represents the extreme of a continuum of normal variability in behavior (Rutter & Sroufe, 2000). But our attempts to respond to this idea probe deeply into philosophical questions about the very nature of mental health. And our conclusions will shape decisions about nosology, diagnosis, and treatment, while shedding light on such persistent problems as the “medicalization of normality” (Craighead, Miklowitz, & Craighead, 2017). The implications – for society, research, and clinical care – cannot be overstated.
In this paper, we will briefly review the history of dichotomous, discontinuous thinking about psychopathology and then describe its gradual evolution to a more continuous, dimensional approach. We will also contemplate the structural and subjective implications of this change as our field moves forward.
The old dichotomies
The history of psychology is littered with dichotomies. In 1840, a crude attempt at classifying mental disorders in the U.S. used a single category – “idiocy/insanity” – implying that people were either sane or not (Krieger, 2019). The present-day authority on psychological classification, the Diagnostic and Statistical Manual of Mental Disorders (DSM–5), has obviously expanded the number of possible diagnoses and employed more sensitive language, but it remains rooted in dichotomous thinking. The DSM is routinely criticized for its arbitrary cut-offs and categorical definitions (Kotov et al., 2017; Krueger & Markon, 2006; Widiger et al., 2019). It perpetuates a narrative of “sick” versus “healthy” and “abnormal” versus “normal,” echoing scenes from an earlier time, when state hospitalizations prevailed and the mentally ill were closeted away from the rest of society. Per DSM thinking, a person is “disordered” or not, and never the twain shall meet.
Perhaps discontinuities in our nosology reflect deeper discontinuities in our research. For decades (or even centuries), the mantra of “nature versus nurture” governed our ideas about etiology. It was thought that biology and environment had competing and orthogonal roles to play in determining behavior; causes were black-and-white, not shades of gray. Biological determinists and social constructionists stood helplessly on opposite sides of the aisle (compare, for instance, Szasz [1960] and Kendell [1975]). The demarcation line remained, as always, strict and impenetrable.
A cracked foundation
But the foundation of our old dichotomies has begun to crack. Evidence is mounting that the traditional way of thinking about mental health and illness – as discontinuous entities – fails to capture reality in truthful ways.
We see the failure of existing models in two related clinical phenomena: the comorbidity crisis (the observation that mental disorders co-exist at frequencies far exceeding expected base rates) and the overreliance of clinicians on “Not Otherwise Specified” diagnoses (Hyman, 2010; Kruger & Markon, 2006). These phenomena point to inadequacies in the DSM, as the manual fails to provide both non-redundant and comprehensive pictures of mental disorder. Some authors propose that comorbidity is artifactual, derived from mistaken concepts and boundaries (Rutter & Sroufe, 2000). Since disorders co-occur more often than expected, we observe meaningful degrees of overlap, which in turn suggests that a continuous, rather than discontinuous, set of underlying mechanisms may be at work.
Another threat to prevailing dichotomies comes in the downfall of “nature versus nurture.” Scientists have by and large abandoned this simplistic line of thinking, turning their attention to more complex concepts like gene-environment interplay (Jaffee, Price, & Reyes, 2013; Rutter & Sroufe, 2000) and interacting risk and protective factors (Cicchetti, 1993). It is clear that the development of a mental disorder runs a complicated course, straddling experiences of stress and resilience in sometimes unpredictable ways (Masten, 2006).
Researchers have started to embrace transdiagnostic models as a way of capturing these complex interactions (Nolen-Hoeksema & Watkins, 2011). Meanwhile, new findings in the field of molecular and behavioral genetics may help us parse complicated linkages and determine whether differences between extremes and normal variation are statistically significant (Rhee, Feigon, Bar, Hadesishi, & Waldman, 2002). As quantitative and conceptual modeling evolve, we see a gradual shift occurring toward a more dimensional approach to mental health and disorder.
Moving toward a dimensional approach
Developmental psychopathology has been a forerunner in integrative, whole-systems thinking. One of the principles on which the discipline rests is the “mutually informative principle” – that is, the belief that studying abnormal development tells us something important about normal development, and vice versa (Masten 2006). This principle suggests that an essential connection exists between maladaptivity and adaptivity, and that these states cannot be understood apart from each other.
Other disciplines intuit the importance of this connection, too. Scientists in the field of personality and temperament research, for example, have established a well-respected dimensional model of classifying personality disorders (Clark, 2005). In this model, a person can possess various levels of a characteristic and disorders are classified according to which characteristics are expressed at which levels. At their extremes, innate temperament dimensions become risk factors for psychopathology, especially under stressful conditions. Binary thinking gives way to dimensional thinking; levels, rather than absolutes, become our guideposts.
Harkness, Reynolds, and Lilienfeld (2014) also nod to the continuities between “normality” and “abnormality” in their Review of Systems (ROS) model. They propose that psychology should comprise the study of “underlying mental operations that serve adaptive purposes,” and they describe five major adaptive systems (like reality modeling for action and short-term danger detection) that appear to be universally enduring among human beings. Stable individual differences in these adaptive systems, according to the ROS, manifest themselves as personality and its disorders. In this way, universal evolutionary processes serve as a template for understanding variations and deviations in human behavior.
Implications for the future of psychology
The movement toward a more dimensional understanding of mental health and disorder brings complex questions to light. In the first place, it prompts us to ask: how will we update our structural systems to view abnormal behaviors as continuous rather than discontinuous with “normality”? Existing paradigms like the DSM do not give us the flexibility in thinking about health and disorder that incoming evidence demands. New research frameworks like the Research Domain Criteria (RDoC) project may break us free from old, constrictive ways of thinking (Sanislow et al., 2010). While not aspiring to diagnostic purposes per se, RDoC promotes commitment to systems-wide research and bottom-up processing across the range of human functioning. Given the dearth of large-scale studies on the continuities and discontinuities of behavioral variation, RDoC (alongside complex models like the ROS) may fill an important gap.
Meanwhile, our ability to understand mental disorder concurrently with mental health suggests broad changes to our view of the human condition. Many have noted the disturbing problem, insidious in psychology, of pathologizing or medicalizing normality. We recall, for instance, the controversial decision to permit diagnosis of major depression as soon as two weeks following the death of a loved one (Craighead et al., 2017). If we retain categorical ways of thinking, we risk turning something like grief into a discrete disorder, rather than a normal experience of suffering embedded in the act of living.
Finally, we anticipate changes in the way society at large thinks about mental illness. If we come to see disordered behavior as an extension of normal behavior, and not as a foreign entity, we may reduce the stigma that has long plagued our field. As a result, we pave the way for greater help-seeking and increased accessibility of psychological services. Moreover, we begin to balance our focus on pathology with an emphasis on vitality, understanding that health and illness, resilience and distress, are deeply interwoven and mutually informative states of being.
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