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Naturalizing psychopathology—towards a quantitative real-
world psychiatry
Juha M. Lahnakoski
1,2
✉, Simon B. Eickhoff
1,2
, Juergen Dukart
1,2,5
and Leonhard Schilbach
3,4,5
© The Author(s) 2021
Molecular Psychiatry; https://doi.org/10.1038/s41380-021-01322-8
Psychiatric disorders continue to be on the rise around the globe.
Meanwhile, efforts and investments directed to early diagnosis
and appropriate interventions for mental health problems are
lagging resulting in ‘substantial loss of human capabilities and
avoidable suffering’[1]. A major component of our inability to
address mental health problems resides in the persistent lack of
objective measures for evaluating such difficulties in the daily life
of individuals, complicating the detection of clinically relevant
changes in the patients’well-being [2]. Similarly, most studies into
the neurobiology of psychiatric disorders lack a detailed descrip-
tion of individual functioning despite influential calls for
quantitative approaches to psychopathology.
Psychiatric conditions are often particularly reflected through,
and exacerbated by, difficulties in social functioning in everyday
life [3]. Yet, current diagnostic evaluations primarily take the form
of limited interactions in artificial clinical settings. While these
types of diagnostic procedures have clear clinical value, they are
often subjective and qualitative in nature. Reports provided by the
patient may suffer from memory biases and can also depend on
the rapport and trust between the patient and the clinician.
Concurrently, standardized questionnaires probe a limited set of
functional impairments and are administered only infrequently
during clinical consultations. With the slow onset and the non-
specific and transient nature of functional impairments in
psychiatric conditions, these limitations may prevent a more
comprehensive description and early detection of psychopathol-
ogy [1].
We argue that a thorough understanding of the real-world
manifestations and implicationsofpsychiatricdisordersisthe
key for the field to move towards the development of more
effective personalized assessments and interventions. To
address this, we outline a general multilevel framework for
deep behavioural phenotyping to guide the scientificinquiry
into the behavioural and neural mechanisms of psychopathol-
ogy and to delineate specific therapeutic interventions (Fig. 1).
This approach emphasises an objective and continuous evalua-
tion of psychopathology in everyday life and naturalistic social
interactions (green box, top left) to guide clinical practice and
scientific research.
The most debilitating symptoms of psychiatric disorders may
only manifest in everyday life, where patients must cope with
multiple aspects of life simultaneously (illustrated by the red scale
at the bottom of Fig. 1). Current technologies can enable detailed
and objective monitoring of the impact of mental health problems
on everyday life of the patient based on their natural behavioural
patterns. One way to achieve this is by measuring daily behaviour
using personal smart devices, often referred to as “digital
phenotyping”[4]. Using these devices, everyday life behaviour
can be assessed passively, for example by objectively measuring
the amount of physical activity or phone-based social interaction.
Moreover, temporal patterns of user interface inputs may provide
valuable insights into psychomotor symptoms such as agitation or
retardation.
Importantly, these passive measures of daily behaviour can be
complemented by subjective ecological momentary assess-
ments providing real-time self-reported measures of patients’
well-being. Such subjective momentary evaluations may prove
crucial to understanding changes in passively monitored
behavioural patterns. For example, while single passive mea-
sures may not be sufficiently discriminative, negative mood
evaluations in combination with reductions in locomotive
activity, social application usage and speed of typing may
represent early signs of a depressive episode. Detecting such
patterns offers a chance for early intervention to avoid
hospitalization (arrow 1. In Fig. 1).
While such digital phenotyping can address macroscopic
aspects of social and motor functioning, it lacks specificity for
assessing how these problems relate to difficulties the patients
face during real-life social interactions. To address this, recent
studies have started to objectively measure behaviour during
social interactions using motion tracking techniques to detect e.g.
individual differences related to interaction success [5] and
behavioural predictors for psychiatric disorders and therapeutic
outcomes [6]. Such tracking techniques can be used to evaluate
psychomotor symptoms in more detail based on face and whole-
body movements. Moreover, some of the symptoms or beha-
vioural tendencies of a person may manifest more strongly during
a dyadic real-time interaction rather than during interaction with a
digital user interface. In a clinical setting, such fine-grained
characterization of behaviour during dyadic interactions may
assist a clinician to reveal subtle early signs for interpersonal
difficulties before symptoms develop into a fully-fledged psychia-
tric disorder. Such behavioural measures can also be extremely
beneficial for elucidating the neurobiological underpinnings of
psychiatric disorders and the behavioural and neural mechanisms
of psychotherapeutic interventions (arrow 2. In Fig. 1). Moreover,
Received: 28 May 2021 Revised: 8 September 2021 Accepted: 24 September 2021
1
Institute of Neuroscience and Medicine, Brain & Behaviour (INM-7), Research Centre Jülich, Jülich, Germany.
2
Institute of Systems Neuroscience, Medical Faculty, Heinrich Heine
University Düsseldorf, Düsseldorf, Germany.
3
LVR-Klinikum Düsseldorf, Düsseldorf, Germany.
4
Medical Faculty, Ludwig-Maximilians-Universität, München, Germany.
5
These
authors contributed equally: Juergen Dukart, Leonhard Schilbach. ✉email: j.lahnakoski@fz-juelich.de
www.nature.com/mp
Molecular Psychiatry
combining behavioural and physiological measurements during
immersive virtual reality may expand the behaviours that can be
evaluated, and have shown promise as generalizable predictors of
individual susceptibility to stress, which is an important contribut-
ing factor to psychiatric disorders [7].
To date, most studies focusing on the neural bases of
psychiatric disorders performed categorical comparisons of
psychiatric disorders while overlooking the extensive variability
in how the disorders manifest in individual patients. Whilst
replicable brain-based group differences appear to exist [8],
group-level effect sizes are often small and the measures may be
more indicative of the general level of psychopathology across
multiple disorders [9]. Progress in machine learning techniques
may improve the specificity of imaging-based biomarkers in the
future. However, it is also increasingly recognized that neurobio-
logical changes might be more strongly associated with
combinations of dimensions of psychopathology than general
clinical labels. Comprehensive behavioural phenotyping may help
uncover clinically relevant behavioural patterns and provide a
window into individual, rather than group-based, neurobiological
underpinnings of psychiatric disorders.
Several approaches could be used to measure the neurobiolo-
gical and physiological correlates of psychiatric disorders from
stable anatomical properties to short-term functional changes
during naturalistic experimental conditions (we illustrate some
options in Fig. 1). Behavioural symptoms are likely not equally
reflected at all levels of this continuum. For example, transient and
context-specific difficulties in social life may not be reflected as
anatomical differences at scales visible in standard anatomical MRI
images. By contrast, exposure to disorder-relevant stimuli may
elicit readily detectable activity differences. Conversely, these
differences may reflect the effect of the conditions while the
causes may lie in pathophysiological alterations at a different
scale. Thus, it is important to critically evaluate which measures
are most reflective of, and contributing to, psychopathology.
Such insights from combining behavioural and neuroimaging
markers of psychopathology may be key for detecting clinically
applicable biomarkers for psychiatric disorders that can feed back
into clinical practice (grey arrow in Fig. 1) and enable novel
insights into the brain mechanisms underlying individual psycho-
pathology [10].
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Fig. 1 Graphical summary of a framework for multiscale assessment of psychopathology. Our framework emphasizes deep behavioural
phenotyping in natural conditions of everyday life and minimally constrained interactions (green box, top left). These approaches can (1)
provide objective measures of daily functioning that can directly guide early detection and individual intervention strategies in the clinic, thus
helping with the limitations of in-clinic evaluations. Additionally, (2), the individual measures of daily functioning may help to uncover
neurobiological markers of the symptom dimensions without relying on heterogeneous disease labels. These findings may then feed back to
clinical practice.
J.M. Lahnakoski et al.
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Molecular Psychiatry
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AUTHOR CONTRIBUTIONS
JML: Conceptualization, writing—original draft preparation, visualization. SBE:
Conceptualization, writing—review & editing. JD and LS: Contributed equally,
conceptualization, writing—review & editing, supervision.
FINANCIAL DISCLOSURES
Work was supported by a grant from the Max Planck Society for an Independent Max
Planck Research Group awarded to LS. SBE acknowledges support by the Helmholtz
Portfolio Theme “Supercomputing and Modeling for the Human Brain,”and the
European Union’s Horizon 2020 Research and Innovation Programme (Grant Nos.
785907 [HBP SGA2] and 945539 [HBP SGA3]). Open Access funding enabled and
organized by Projekt DEAL.
COMPETING INTERESTS
The authors declare no competing interests.
ADDITIONAL INFORMATION
Correspondence and requests for materials should be addressed to Juha M.
Lahnakoski.
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© The Author(s) 2021
J.M. Lahnakoski et al.
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Molecular Psychiatry