Neurobehavioural Functioning
PBL sessions
, Task 1 – A Matter of Definition… and of Assessment
Learning goals
1. What does neurobehavioural functioning entail?
2. What may cause discrepancies in results (methodological, machine, etc.)?
3. What is the classical approach and the continuum approach?
4. What are the pros and cons of both approaches?
5. What is the definition of RDoC and HiTOP?
6. What defines an individual position on the continuum?
7. Can the dimensional approach be informative in terms of diagnosis?
(1) ESTERBERG: THE PSYCHOSIS CONTINUUM AND CATEGORICAL VERSUS
DIMENSIONAL DIAGNOSIS
This paper discusses the dimensional approach to understanding psychotic experiences. The current
system for diagnosing mental disorders is the DSM-IV-TR, which adopts a categorical approach. This
has evolved from Emil Kraepelin, who coined the ‘Kraepelinean dichtomy’. This approach to the
diagnosis of schizophrenia has continued to guide psychiatric classification systems. However, this
categorical approach has been criticised. Psychotic symptoms occur among a much broader segment
of the population than just those with traditionally defined psychotic disorders.
EVIDENCE FOR A CONTINUUM OF PSYCHOSIS
Self-reported psychotic symptoms in the general population:
There is a higher prevalence of reported psychotic experiences (e.g. paranoid ideation) than
diagnosable psychotic illness in the general population. In the Netherlands:
o The prevalence of delusions + hallucinations = between 8.7% and 6.2%.
o Among those with any type of psychosis rating only 2.1% was diagnosed with a
non-affective psychotic disorder.
BUT There is an association between self-reported psychotic symptoms and stressful life
events or perceived stress, depression, and impulsivity. Psychotic symptoms may also reduce
quality of life.
THEREFORE It is beneficial to clarify which features of psychotic symptoms (e.g.
frequency, degree of conviction, preoccupation, influence on behaviour) distinguish
(relatively) normal experiences from more disabling ones.
o Example = research suggests that specific dimensions of delusions may be relevant in
distinguishing relatively normal experiences from more disabling ones.
Schizotypal traits
Schizotypy = describes a range of psychosis-related experiences representing a portion
of the schizophrenia spectrum
Thus, schizotypy encompasses a continuum of traits ranging from
psychotic-like experiences that occur in the general population to more
severe symptoms that lead to a schizotypal personality disorder (SPD)
or indicate the onset of a psychotic disorder.
Meehl described schizotypy as a clinical manifestation of schizotaxia, but
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, later noted that not all individuals with schizotaxia develop schizotypal
features, SPD, or schizophrenia.
Schizotaxia = refers to the genetic liability for schizophrenia (however not only for
schizophrenia, also broader biologic liability).
Largely unexpressed
The genetic liability can be high but you don’t necessarily develop
schizotypal features/SPD/schizophrenia.
It is not only a genetic liability for schizophrenia, but also for a broader
biologic liability. Many researchers have come to consider schizotaxia as
a significant clinical condition characterised by subtle neuropsychological
deficits + negative schizophrenic symptoms.
Note: some researchers consider schizotaxia + schizotypy to be the same.
Schizotypal P.D. = a nonpsychotic syndrome related to schizophrenia.
(SPD)
Factors underlying SPD = cognitive-perceptual deficits, interpersonal
difficulties, disorganisation + paranoia.
NOTE: most do not become psychotic.
Schizotypy was introduced in the DSM-4-TR s SPD to help distinguish
people with relatively normal variations in schizotypy from those who
manifest clinically relevant levels of schizotypy traits.
The DSM-5-TR classifies it as the Axis II disorder, which is a pervasive
pattern of social + interpersonal deficits marked by acute discomfort
with, +reduced capacity for, close relationships as well as by cognitive or
perceptual distortions + eccentricities of behaviour, beginning by early
adulthood and present in a variety of contexts.
Diagnosis requires 5/9 SPD features.
Debate = should SPD be diagnosed categorically or dimensionally?
Research suggests that schizotypy + SPD = multidimensional + fam
members of schizophrenic patient differ from nonrelatives based on the
type + severity of schizotypal features.
HENCE = are there different schizotypal disorders? Would SPD be best
captured by a dimensional diagnostic approach given its heterogeneity?
Psychosis and Psychotic Disorder
Some of the previously mentioned manifestations of the psychosis continuum may remain
relatively unobserved by mental health professionals. That is, while symptomatology in the
broader population generally exists as a continuum of severity, in clinical practice, disease is
often (perhaps mistakenly) seen as an all-or-nothing phenomenon.
In a dimensional approach, primary psychotic disorders (e.g. schizophrenia) is at the most
severe end of the continuum + least prevalent among manifestation of psychotic experience.
Substantial psychosocial disability demarcates the boundary of psychotic disorders long the
psychosis continuum.
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, CATEGORICAL VS DIMENSIONAL APPROACHES TO THE DIAGNOSIS OF PSYCHOSIS
Pros of Categorical Approach Pros of Dimensional Approach
It facilitates the decision making process. Higher validity It reflects the true
The presence of a diagnosis necessitates continuum of psychosis in the population +
treatment, while the lack of a diagnosis captures its high degree of heterogeneity +
negates the need of treatment. The variation.
diagnostic system provides a frame of It removes the loss of information that
reference for treating patients. occurs when continuous-level data are
Pro for research there is consistency organised + greater statistical power.
across studies (e.g. cut-off criteria), cost- It explains comorbidity + symptom overlap
effectiveness (costly and high-risk likely due to shared susceptibilities.
treatments are kept for those who cross Higher predictive power for clinical
thresholds), + it allows comparison of symptoms, treatment response and
studies resulting in more information. outcomes.
Improves diagnostic reliability There is
more agreement, consistency, and stability.
Improves communication among clinicians,
researchers and the lay community. It is a
good method for understanding a particular
syndrome.
(2) FRIED: MENTAL DISORDERS AS NETWORK OF PROBLEMS – REVIEW OF
RECENT INSIGHTS
This paper provides a review of all network studies published between 2010 and 2016 and discusses
them according to three main themes: comorbidity, prediction, and clinical intervention.
Pertaining to comorbidity, the network approach provides a powerful new framework to explain
why certain disorders may co-occur more often than others. According to this approach, a mental
disorder can be viewed as a system of interacting symptoms. It is easy to envision causal
relationships between these symptoms.
Example = MDD symptoms are fatigue insomnia concentration problems sadness,
anhedonia and suicidal ideation.
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