Djebbara, Z., Jelic, A. and Fich, L. B. (2022) ‘Tying architecture and homeostasis using affordances: An approach to well-being in the built environment’, in Structures and Architecture. A Viable Urban Perspective?: Proceedings of the Fifth International Conference on Structures and Architecture (ICSA 2022), July 6-8, 2022, Aalborg, Denmark. CRC Press, p. 353.
Link to the proceedings right here!
Abstract
In framing human well-being in the built environment as the support of the emotional, mental and physical health of the users, an approach that addresses that particular interface is principal. For the built environment to support well-being, this human-centered approach must integrate an understanding of the interplay between architectural space and the physiological and psychological processes that underly behavioral, mental, and cognitive functions. In this contribution, we draw a qualified approach by bridging brain, body, environment through ‘affordances’, namely the fit between the physical structure of the body and the potential possibilities for movement and interaction with the environment. Starting in homeostasis, we link affordances with sensorimotor brain dynamics, on which cognitive processes are based, to propose a biologically plausible view on human well-being through the design of the built environment.
Introduction
Understanding how the built environment affects human well-being using a combination of neuroimaging, physiological measures, and systematic architectural variation is still in its early stages. The recent empirical results display a wide field of interest, including aesthetic experiences (Vartanian et al., 2013, 2015), the role of the body (Vecchiato et al., 2015; Banaei et al., 2017), of action (Djebbara et al., 2019; Djebbara, Fich and Gramann, 2021), of affective processes (Fich et al., 2014; Shemesh et al., 2017), and of atmospheres (Canepa et al., 2019)—all of which have a human-centered approach. Collectively, these studies demonstrate how features of the environment have an implicit impact on our decisions and physiological processes, which together constitute a major part of our well-being. This is particularly important to better our comprehension as the built environment continues to affect us in unbeknownst positive or negative ways.
In this paper, we propose a psychobiological framework for well-being in the built environment with the starting point in the biology of human beings and argue for the importance of the dynamics between sensation and action in the psychological measures of well-being. The motivation for proposing such a framework is twofold. First, to contribute to the advancement of this very young field, the following aims to suggest a way of linking the built environment with the mental and physical health, which we associate with the general well-being of human beings, by using the emerging dynamics between brain, body, and environment as the common denominator. Second, as we unpack our framework, we discover that in our psychobiological approach to well-being, the preconceived distinction between mental and physical is indeed difficult, if not impossible, to defend. Instead, they form a unity where mental and physical parameters are inherently related to the forming of well-being in a circular fashion. We argue that these types of well-being all emerge from the very same dynamics found between brain, body, and environment and are thus considered coherent and inseparable. This naturally implicates that the study of physical well-being is thus also subject to mental parameters, and vice versa.
In applying this framework we review major depressive disorder as a case study because it applies to well-being. By focusing on the role of the built environment, we suggest how changes in everyday affordances can alter how we understand our relation to the world, essentially causing a shift in perspective that is known to have a positive impact on depressive patients. The relationship is bidirectional, so to change how we act is also to change the trajectory of thoughts and eventually a change of the mind, and vice versa. How did the built environment become this important to human beings?
Homeostasis and prediction
By first introducing the biological history of human beings, we provide a proper grip of the very nature of how remaining alive and making sense of the environment are related. This argument builds around the conception that as life evolved, certain interactive capacities co-evolved with increasingly sophisticated biological structures that eventually paved the way for the human capacities we know today. Due to the continuous phylogenic process, we have many features in common with primitive creatures—in particular, that of staying alive (see e.g. Godfrey-Smith, 2020).
In the biological realm, the relationship between a cell and its environment is manifested in the various parallel processes unfolding to ensure its survival. Biochemical processes releasing chemicals to counterbalance the constant fluctuations generated by the environment are constantly taking place. The emerging balance aims to withhold the physiological processes of the organism within a narrow acceptable interval—this process is referred to as the homeostatic balance and is a basic process in all living cells (Damasio, 2010). If, for instance, the environment is sensed to be too cold, the organism must avoid homeostatic imbalance by accounting for the error (cold) by either moving to a warmer place or by generating heat through shaking and thereby regaining balance. Besides that some environments are more suitable for some organisms while potentially lethal to others, it is important to notice that survival chances are contingent on the interactive capacities of the majority of organisms. As we will elaborate, the interactive fit between an agent and its environment can be described by the affordances of the organism inherent to the physical structure of the organism and its potential for action (Gibson, 1986; Clark, 1999). However, for now, it is important to emphasize the importance of the environment for physiological changes in the body.
Therefore, organisms that remain to exist owe it to their capacity to self-organize homeostasis and reproduction while optimizing their respective strategies of these processes of life (Maturana and Varela, 1992). An important strategy is the ability to anticipate the error using cues in the environment, which essentially allowed initiating changes before the potentially lethal error could take place, e.g. putting on a jacket before getting a cold (Sterling, 2004). For an organism to remain alive, the most basic requirement is to implicitly engage in this error-correcting mechanism contingent on the numerous surprising observations one can sense about the environment. This process of instinctive prediction is entirely automatic. The objective is then to predict changes using the network of neurons in the brain before errors happen and avoid repulsive encounters by either (i) initiating internal physiological changes or (ii) initiating actions that cause the environment to change (Friston, 2010). Certain encounters emphasize the internal physiological changes reflected as emotions, while other encounters emphasize the movement—however, both processes are constantly unfolding. We will focus here on the possibilities for movement afforded by the environment given the human physical structure.
With increasingly complex and sophisticated organisms comes also more sophisticated capacities and functions such as complex movements, the extension of memory, capacities for planning, and abstractions. In other words, the cells have used their inherited prior experiences to develop highly qualified and temporally extended predictions about the environment given specific contextual cues. For instance, knowing it is winter season, you would have a specific expectation about the weather and thus type of clothes to wear, which words to use, what city decorations to see, and how to spend the evenings, as compared to the summer season. Essentially, our framework suggests that there is a bidirectional hierarchy to our predictions so that we can both infer from sensations (bottom-up) and from situations (top-down). The hierarchy is bidirectional so that it is both made of numerous small predictive processes that gradually form bigger contextual predictions[1], as well as bigger predictive processes that shape the smaller processes[2]. These contextual predictions are precisely what directs our emotions and actions so that contextual cues, e.g. being in a church, are continuously picked up and used to guide behavior, e.g. being silent.
According to this view, the homeostasis and the predictive nature of our biology account for a major part of our biological processes. Moving from broad strokes in biology to more concrete human beings, we want to briefly discuss the nature of acting and perceiving under the conviction that we have a predictive nature.
Sensorimotor dynamics
The term ‘dynamic’ refers to the pattern of change as the “[…] phenomena that produce time-changing patterns, the characteristics of the pattern at one time being interrelated with those at other times” (Luenberger, 1979, p. 1). At any moment, the sensation we have is interrelated with that which just has immediately passed and that which is immediately incoming. The ecological psychologist James J. Gibson emphasizes this particular point by indicating that discrete, individual stimuli cannot exist (Gibson, 1950). To Gibson, the prescriptive use of the concepts stimulus and response are problematic as they presume that both stimulus and response are temporally and spatially distinguishable from the incoming and outflowing array of sensory information and response. When analyzed from a temporal perspective, this view assumes that there is an instantaneous transition from one stimulus and response to another.
However, as an ecological alternative, stimuli are instead considered an array of energy with overlapping stimulus and responses occluding one another, which means that at any moment, any stimulus, as it were, cannot be considered in isolation as it is never detached from neither its prior nor incoming stimulus and response (Gibson, 1977; Spivey, 2008). Sensations and responses endure and are continuous while contingent on the dynamics of the brain, body, and environment—they co-exist through co-conditional sensory and motor dynamics. From this continuous view on cognition as process-oriented instead of substance-oriented (Rescher, 2000; Heraclitus, 2003; Nicholson and Dupré, 2018), it follows that there are no sudden changes or jumps neither in sensory flow nor in human experience. Rather, there is a flowing trajectory reflecting our behavior partially as a consequence of the environmental instances constituted by events, objects, and other human beings. It is in this sense that sensations and the processing thereof are directly related to our actions and the potential for action.
Fitting the body
By integrating the body and environment with the brain in understanding our well-being, we inevitably buy into an embodied view of cognition (Beer, 2008; Varela, Thompson and Rosch, 2016). Central to this view is the fit between the physical structure of the body and the potential possibilities for movement and interaction with the environment. This particular fit describes the relationship between an agent and its environment, typically referred to as the agent-environment system (Beer, 1995). As mentioned, this fit is described by the relational entity ‘affordances’, which essentially describes the relation, in terms of acting and perceiving, between an agent and its environment. Notice here that ‘perception’ requires a specific relational attitude towards the environment to make the leap from mere ‘sensation’ to understanding the environment. In other words, affordances reflect embodied predictions related to possible actions and desired external sensations and internal changes (Pezzulo, Rigoli and Friston, 2015; Friston et al., 2017). For instance, when feeling cold and one observes a spot of sunshine, that spot has better affordances (it affords to not be cold, which is desired and thus better) than remaining in the shadow.
Now, if our account is correct, then the sensory systems depend on the same underlying process as for acting, meaning their sensorimotor dynamics can reveal a great deal about the affordances of the users. In other words, the intimate relation between affordances and sensorimotor dynamics suggests that the state of the body and brain highly depends on the encounters with the environment. From an architectural point of view, this means that built architectural spaces constitute the affordances the users encounter in the designed office, living room, bedroom, city square, metro station, airport, classroom, etc. The built environment is difficult, if not impossible, to escape.
Some evidence is starting to surface for the importance of affordances on well-being. The impact of architectural affordances on the human stress system was investigated by Fich et al. (2014). Based on the literature on the fight-or-flight mechanism, they designed a social stress test experiment where cortisol levels would reflect the activity of stress levels. By conducting the social stress test in an open space, where one affords to leave the room, and a closed space, where one does not afford to leave, they showed that cortisol levels were significantly lower in spaces that afford to escape. By appealing to the hormonal system, the responses are slow and thus reflect internal and external changes at a temporal scale of minutes. Faster systems, such as the central nervous system, are reflected in the synaptic activity in the brain that another study attempted to record while varying the affordances of the built environment.
This study was conducted by Djebbara et al. (2019) using a mobile electroencephalogram (EEG) and Virtual Reality to measure the sensorimotor activity of the participants while crossing from one space into another one with varying widths of doors. Of three possible doors, the participants would not be able to pass one of them—the door did not afford to pass. As predicted according to the introduced framework, the dynamics of the sensorimotor brain region reflected the affordances of the doors. There was a significant and systematic change the followed the pattern of affordances of the doors so that the two passable doors did not significantly differ whereas this was the case for the impassable door compared to the others. This holds for both the initial perception of the doors and the continuous process while approaching the doors (Djebbara, Fich and Gramann, 2021).
Interestingly, these studies show that affordances of space affect the hormonal system and the coupling in the sensorimotor system, which according to our view of well-being appears to be critical systems. They thus serve as shreds of evidence that architectural affordances, through the lens of psychobiology, can affect mental, emotional, and physical well-being. The question remains whether there are any examples to demonstrate how this may be applied to encourage and in favor of well-being.
A case in psychopathology
We touch briefly on the major depressive disorder as it serves as an example of the absence of mental, and/or physical well-being. Following the report by American Psychiatric Association on Major Depressive Disorder (MDD)[3] (Gelenberg et al., 2010), common features in MDD include disturbed sleep pattern, appetite, or sexual desire, cognitive dysfunctions where slowed thoughts, poor concentration, distractibility, and reduced capacity to process information were common traits reported by patients. Moreover, diminished attention to self-care and their environment is also displayed by the patients (Belmaker and Agam, 2008; Gelenberg et al., 2010, pp. 60–61). With a massive loss of vitality and ability to enjoy life, the disorder affects the way one feels, thinks, and behaves—these are thus precisely also where the symptoms show.
Particularly stress in the form of cortisol is hypothesized to be involved in depression (Belmaker and Agam, 2008). Without unpacking the anatomical details, it suffices here to know that changing the affordances of the environment also had an impact on the cortisol levels of the users of the space. To be sure, we are not suggesting to perform some reverse inference to conclude that experiencing architecture and having a depression share the same underlying neural mechanisms. Instead, we suggest that designing spaces carefully customized to the affordances of the depressive patients could function like a system of scaffolds towards better concentration, less distractibility, better memory, and so forth.
As our framework emphasizes the sensorimotor system, we also briefly suggest how architectural affordances relate to MDD here. Studies on MDD patients show a reduced thalamic volume (Bora et al., 2012), while electroconvulsive therapy shows volumetric changes in the thalamus are associated with clinical improvements (Takamiya et al., 2020; Wei et al., 2020; Jehna et al., 2021). This is particularly interesting as all sensory information (except olfaction) about the body itself and the immediate environment is relayed through the thalamus, located in the deep brain structures, to the neocortex, located around the deep brain structures (Buzsáki, 2006, p. 177). Thus, the thalamus becomes a critical gate regarding communication between sensory and motor processes in the central nervous system. Furthermore, a new study demonstrates that sensorimotor information flow reflects the severity of depression serving now as a potential signature for clinical use (Ray et al., 2021). Taken together, these studies suggest that sensorimotor brain dynamics are useful to understand the severity of depression and thus function as a signature. Interestingly, as both architectural affordances and the severity of the depression are reflected in sensorimotor areas of the brain, it implies a possible, but unexplored, relation between the design of the environment and the depressive disorder. To unfold how this relation could be speculatively be related, consider the following simplified example.
Consider rearranging your bedroom and living room by moving around the bed, the dinner table, the office table, the books, and posters, etc. All routine movements can no longer unfold in the newly arranged spaces. Notice here that the interaction with the environment was shown to be reflected in the sensorimotor dynamics—similarly, depression-associated changes are identified in the flow of information in the very same dynamics. For instance, in the study by Ray (2021), it was discovered that signals with roots within the body were augmented, while signals from the environment were depreciated, which is typical of depressive symptomatology. Broadly speaking, changing the habituated environment, could generate a feeling of novelty to the routined user, forcing a new interpretation of their relation to the world and thereby enhancing the signals rooted in the environment. The simple alteration of affordances in the space will, according to our view, affect the relationship between body, brain, and environment—however, whether it is a positive or negative change remains up to the individual interpretation. In other words, a new space could mean ‘a new interpretation of me’. The key here is to create changes in the routine environment to enforce new interpretations of the body’s and brain’s relation to the environment. Rearranging the affordances to rearrange our relation with the world is but one speculative suggestion. In line with this thought, the environment can be changed through traveling as well. We emphasize that these suggestions are meant as supports of an extremely serious disorder. There will be challenges, e.g. making the effort to move things around or book traveling tickets, where affordances may serve in a different way, e.g. accessible office and furniture.
Whatever next?
We have attempted to establish a psychobiological framework that ties architecture, homeostasis, and affordances together to form an approach to understand well-being from the view of the built environment. By basing our argument on homeostasis and the emergent predictive nature, we have both a biological and cognitive fundament that takes the whole psychophysiological view seriously. If we understand emotions as the current physiological outcome of the interplay between brain, body, and environment, then we must necessarily integrate environmental features in our thinking and reasoning about the behavioral, bodily, and cortical states that we typically take to reflect well-being. To emphasize the importance of the body, social and affective neurosciences have claimed that since the human capacities that are important in school environments, e.g. learning, attention, memory, social functioning, and decision making, are deeply affected by emotional processes as these guide judgment and action, then a better understanding of the underlying neurobiology must form a new basis for the designing of learning environments (Immordino-Yang and Damasio, 2007).
The use of affordances has served as an important step from biological and cognitive processes, typically considered to be body and brain-related, towards the built environment. Affordances then serve both to inform us about the cognitive processes and the built environment as this embodied view suggests there is an intimate link. Applying this framework to MDD to demonstrate how one might use the environment to address sensorimotor dynamics have served as a medium to explain how architects can be more cautious about the users and to explain how a human-centered design approach could look like.
From a research perspective, the use of mobile neuroimaging techniques with experimental designs that allows natural behaviors to unfold with architectural variability could lead to discoveries regarding how the affordances of space affect the brain. On one hand, psychopathological groups with known brain lesions can reveal what networks in the brain are affected by the changes in the environment. On the other hand, qualitative interviews and questionnaires can also reveal the impact of architectural alterations on the experience. Neurophenomenology is the combination of both as it is a methodological attempt at coupling neuroimaging with subjective reports that involve deep interviews and fine-grained descriptions of experience. Ties between architecture and neurophenomenology have been suggested before (Jelić et al., 2016; Djebbara, 2021).
Essentially, we do not pretend that this framework is complete, but merely state that we have linked the first puzzles together for the many to come in the future, for instance by trying to understand other psychopathologies, the cultural layer of architecture, the importance of architecture during the developmental phase, and so on. In brief, the spaces we inhabit appear to be a part of us.
References
Banaei, M. et al. (2017) ‘Walking through Architectural Spaces: The Impact of Interior Forms on Human Brain Dynamics’, Frontiers in Human Neuroscience, 11(417). doi: 10.3389/fnhum.2017.00477.
Beer, R. D. (1995) ‘A dynamical systems perspective on agent-environment interaction’, Artificial Intelligence, 72(1), pp. 173–215. doi: https://doi.org/10.1016/0004-3702(94)00005-L.
Beer, R. D. (2008) ‘6 – The Dynamics of Brain–Body–Environment Systems: A Status Report’, in Calvo, P. and Gomila, A. B. T.-H. of C. S. (eds) Perspectives on Cognitive Science. San Diego: Elsevier, pp. 99–120. doi: https://doi.org/10.1016/B978-0-08-046616-3.00006-2.
Belmaker, R. H. and Agam, G. (2008) ‘Major Depressive Disorder’, New England Journal of Medicine, 358(1), pp. 55–68. doi: 10.1056/NEJMra073096.
Bora, E. et al. (2012) ‘Meta-analysis of volumetric abnormalities in cortico-striatal-pallidal-thalamic circuits in major depressive disorder’, Psychological medicine, 42(4), pp. 671–681.
Buzsáki, G. (2006) Rhythms of the brain. Oxford: Oxford University Press.
Canepa, E. et al. (2019) ‘Atmospheres: Feeling Architecture by Emotions’, http://journals.openedition.org/ambiances, (5). doi: 10.4000/AMBIANCES.2907.
Clark, A. (1999) ‘An embodied cognitive science?’, Trends in Cognitive Sciences, 3(9), pp. 345–351. doi: 10.1016/S1364-6613(99)01361-3.
Damasio, A. (2010) Self comes to mind. 1. ed. New York: Pantheon Books.
Djebbara, Z. et al. (2019) ‘Sensorimotor brain dynamics reflect architectural affordances.’, Proceedings of the National Academy of Sciences of the United States of America, 116(29), pp. 14769–14778. doi: 10.1073/pnas.1900648116.
Djebbara, Z. (2021) ‘A Neurophenomenology for Architecture: an embodied and enactive inference approach’, in 8th International Conference on Spatial Cognition: Cognition and Action in a Plurality of Spaces.
Djebbara, Z., Fich, L. B. and Gramann, K. (2021) ‘The brain dynamics of architectural affordances during transition’, Scientific Reports, 11(1), p. 2796. doi: 10.1038/s41598-021-82504-w.
Fich, L. B. et al. (2014) ‘Can architectural design alter the physiological reaction to psychosocial stress? A virtual TSST experiment’, Physiology & behavior, 135, pp. 91–97. doi: 10.1016/j.physbeh.2014.05.034.
Friston, K. (2010) ‘The free-energy principle: a unified brain theory?’, Nature Reviews Neuroscience, 11(2), pp. 127–138. doi: 10.1038/nrn2787.
Friston, K. et al. (2017) ‘Active Inference: A Process Theory’, Neural Computation, 29(1), pp. 1–49. doi: 10.1162/NECO_a_00912.
Gelenberg, A. et al. (2010) Practice Guideline for the Treatment of Patients With Major Depressive Disorder. Available at: https://psychiatryonline.org/pb/assets/raw/sitewide/practice_guidelines/guidelines/mdd.pdf.
Gibson, J. (1986) The Ecological Approach to Visual Perception. East Sussex: Psychology Press – Taylor & Francis Group.
Gibson, J. J. (1950) The perception of the visual world., The perception of the visual world. Oxford, England: Houghton Mifflin.
Gibson, J. J. (1977) ‘The Theory of Affordances’, in Shaw, R. and Bransford, J. (eds) Perceiving, Acting, and Knowing: Toward an Ecological Psychology. 1st edn. Hillsdale, NJ: Lawrence Erlbaum.
Godfrey-Smith, P. (2020) Metazoa: Animal Life and the Birth of the Mind. New York, NY, US: Farrar, Straus and Girou.
Heraclitus (2003) Fragments: the collected wisdom of Heraclitus. Edited by B. Haxton. New York: Penguin Books.
Immordino-Yang, M. H. and Damasio, A. (2007) ‘We Feel, Therefore We Learn: The Relevance of Affective and Social Neuroscience to Education’, Mind, Brain, and Education, 1(1), pp. 3–10. doi: https://doi.org/10.1111/j.1751-228X.2007.00004.x.
Jehna, M. et al. (2021) ‘Do increases in deep grey matter volumes after electroconvulsive therapy persist in patients with major depression? A longitudinal MRI-study’, Journal of Affective Disorders, 281, pp. 908–917.
Jelić, A. et al. (2016) ‘The Enactive Approach to Architectural Experience: A Neurophysiological Perspective on Embodiment, Motivation, and Affordances’, Frontiers in psychology, 7, p. 481. doi: 10.3389/fpsyg.2016.00481.
Luenberger, D. G. (1979) Introduction to dynamic systems: theory, models, and applications. 1st ed. United States: John Wiley & Sons, Ltd.
Maturana, H. R. and Varela, F. J. (1992) The tree of knowledge: the biological roots of human understanding. 1st ed. Boston: Shambhala.
Nicholson, D. J. and Dupré, J. (2018) Everything flows: towards a processual philosophy of biology. Oxford University Press.
Pezzulo, G., Rigoli, F. and Friston, K. (2015) ‘Active Inference, homeostatic regulation and adaptive behavioural control’, Progress in Neurobiology. Elsevier Ltd, pp. 17–35. doi: 10.1016/j.pneurobio.2015.09.001.
Ray, D. et al. (2021) ‘Altered effective connectivity in sensorimotor cortices is a signature of severity and clinical course in depression’, Proceedings of the National Academy of Sciences, 118(40). doi: 10.1073/PNAS.2105730118.
Rescher, N. (2000) Process Philosophy: A survey of basic issues. 1st ed. United States of America: University of Pittsburgh Press.
Shemesh, A. et al. (2017) ‘Affective response to architecture – investigating human reaction to spaces with different geometry’, Architectural Science Review, 60(2), pp. 110–116. doi: 10.1080/00038628.2016.1266597.
Spivey, M. (2008) The continuity of mind. Oxford University Press.
Sterling, P. (2004) ‘Principles of Allostasis: Optimal Design, Predictive Regulation, Pathophysiology, and Rational Therapeuticss’, in Schulkin, J. (ed.) Allostasis, homeostasis and the costs of physiological adaptation. 1st ed. Cambridge: Cambridge University Press, p. 372.
Takamiya, A. et al. (2020) ‘Neuronal network mechanisms associated with depressive symptom improvement following electroconvulsive therapy’, Psychological Medicine, pp. 1–8.
Varela, F. J., Thompson, E. and Rosch, E. (2016) The embodied mind: cognitive science and human experience. Revised ed. London, England: MIT Press.
Vartanian, O. et al. (2013) ‘Impact of contour on aesthetic judgments and approach-avoidance decisions in architecture’, Proceedings of the National Academy of Sciences of the United States of America, 110, pp. 10446–10453. doi: 10.1073/pnas.1301227110.
Vartanian, O. et al. (2015) ‘Architectural design and the brain: Effects of ceiling height and perceived enclosure on beauty judgments and approach-avoidance decisions’, Journal of Environmental Psychology, 41, pp. 10–18. doi: 10.1016/j.jenvp.2014.11.006.
Vecchiato, G. et al. (2015) ‘Electroencephalographic Correlates of Sensorimotor Integration and Embodiment during the Appreciation of Virtual Architectural Environments’, Frontiers in psychology, 6, p. 1944. doi: 10.3389/fpsyg.2015.01944.
Wei, Q. et al. (2020) ‘Thalamocortical connectivity in electroconvulsive therapy for major depressive disorder’, Journal of affective disorders, 264, pp. 163–171.
[1] For instance, seeing a person on the roof that is dressed in red and white with a bag over the shoulders climbing down someone’s chimney and then inferring it must be burglars.
[2] For instance, inferring that it cannot be burglars and must be Santa Claus as it is in fact Christmas.
[3] MDD is an extremely complicated and serious disorder that goes beyond the scope of this relative short paper. We will, however, include that as comorbidity is not atypical in MDD, it is difficult to uncover the traits and features of exclusively MDD. The influence of dysthymic disorder, anxiety disorder, dementia, personality disorder, and so forth, complicates both treatment and the identification of MDD, and it is thus more complicated than we portray it in the paper.
Zak's Blog 