A clinically useful model of psychopathology must account for interpersonal dynamics

A useful taxonomy of psychopathology should not only describe variations in mental disorder, but also explain how they occur and point to therapeutic solutions. Contemporary diagnostic models based on a system of polythetic disorder categories do not validly capture the covariation of disorders and symptoms across people, introducing both disorder comorbidity and het­erogeneity. As a result, significant advances in explaining dis­crete categories of psychopathology or deriving disorder‐specific therapeutic solutions have not been forthcoming.

These failures have led to new approaches to psychiatric taxonomy, such as the Research Domain Criteria (RDoC) ¹ and the Hierarchical Taxonomy of Psychopathology (HiTOP) ² . Both of these systems conceptualize symptoms and disorders as dimensions that can be arranged hierarchically, with narrow symptoms being related to one another because of their mutual associations with broader domains. By reconfiguring mental health variables, HiTOP and RDoC provide evidence‐based models of how people differ from one another on average and enable more reliable predictions about what kinds of dysfunctions people are likely to experience.

However, these models are missing two elements that are crit­ical for explaining mental health problems and generating treatments. First, whereas HiTOP and RDoC account for psychopathology solely in terms of elevated levels of certain signs and symptoms within the person, psychopathology manifests as a pattern of dynamic transactions between people and their environments ³ . Persons with psychotic symptoms misperceive information about the world around them; persons with anxious symptoms experience benign situations as threatening; persons with antisocial features experience dangerous situations as exciting, often increas­ing risks to self and others.

Second, neither RDoC nor HiTOP conceptualize how people move dynamically through their lives. Mental health problems and associated dysfunction are generally not constant. They are more often evoked and manifest in certain situational contexts. The psychotic person misperceives certain kinds of things, the anxious person usually worries about certain kinds of problems, and the antisocial person seeks certain kinds of thrills. HiTOP and RDoC can make predictions about which people are more or less likely to experience mental health problems in the abstract, but not when, where, and how these problems will manifest in the situations people encounter in their lives.

Contemporary integrative interpersonal theory (CIIT) is a mod­el of personality and psychopathology built on 70 years of evidence regarding how people differ from one another (what people are like) and how they function in environmental contexts (what people do) ⁴ . Like HiTOP and RDoC, it provides a taxonomic model and suite of well‐validated tools for assessing individual differences in personality and psychopathology ⁵ . However, in contrast to HiTOP and RDoC, CIIT is fundamentally concerned with how people function in the context in which they live. The model has two key features that complement new approaches to diagnosis.

First, CIIT is essentially relational. The transition from understanding individuals in a vacuum to understanding people in context has been a stepping stone across scholarly pursuits. Philosophy became intersubjective when the existentialists understood that Descartes had to be thinking about something. The periodic table was derived from the principle that electrons serve the function of connecting elements with one another. Nuclear power was enabled by Einstein's insight about the connection between energy and time. Major models of psychopathology still operate on the assumption that mental disorder can be understood as something that occurs in a vacuum. In contrast, the first assumption of CIIT is that fundamentally important functional expressions of personality and psychopathology occur in interpersonal situations ⁶ .

In CIIT, the interpersonal situation – encompassing direct in‐person interactions with objects in the environment, most centrally other people, as well as mental representations of interactions, both recollected and imagined – is considered the basic unit of personality and psychopathology ⁵ . In the interpersonal situation, self and other interact through four interpenetrating systems that account for the important features of socio‐affective function and dysfunction. Each system is represented by two‐dimensional circular (circumplex) planes reflecting the major empirically supported dimensions of interpersonal functioning or emotion. The self system is structured by the individual's agentic and communal motives. The affect system is organized around the person's level of emotional arousal and valence. The behavior system includes each person's behavioral dominance and warmth. The perception system reflects each person's perceptions of agency and communion in themselves and the other. The interactions among these systems mark key components of dyadic processes that drive an interpersonal situation, as self and other dynamically cycle through continuous transaction.

Second, CIIT is fundamentally dynamic. It is assumed that the satisfaction of motives for agency (power, status) and communion (connection, love) drive interpersonal behavior. This leads to specific, probabilistic predictions about how people will tend to transact with others via affective, behavioral and perceptual processes, and how that can go wrong. Adaptive functioning is not defined by dispositional levels per se: rather, it is defined by the ability to stably yet flexibly coordinate and satisfy self and others’ motives within the contexts of developmental, socio‐cultural and situational demands. Accordingly, dysfunction reflects sustained breakdown in any of the processes that support and maintain the flexible, stable and effective regulation of self, affect and/or interpersonal behavior.

Circumplex measurement tools have been developed to capture variation in the self, affect and behavior system, and multi‐perspective assessments can be used to capture variations in perception. Such tools include self‐ and informant‐report questionnaires and rating scales, experience sampling via mobile devices, and computer‐facilitated continuous observational assessment methods ⁷ . The dimensions of CIIT and its associated assessment methods can be used to distinguish people from one another, on average, as in HiTOP or RDoC, but they can also be used to describe how people vary from themselves across time and situations. These methods allow for empirical tests of hypotheses about dynamics in group‐based research and in individual clinical cases. Parameters from validated dynamic interpersonal assessment measures have been empirically related to dysfunction ⁸ and psychotherapeutic processes ⁹ .

CIIT moves beyond models that describe how people differ from one another on average, and how those differences pose risk for symptoms, to also account for the context in which those symptoms manifest, and what kinds of environmental transactions can exacerbate or alleviate them. By marrying a structural model of individual differences with a functional model of person‐environment transactions, CIIT supports a fuller understand­ing of personality, psychopathology and intervention, and pro­vid­es a relational and dynamic complement to individual‐based models such as HiTOP and RDoC.