On the Spectrum

General discussion
CLINICAL IMPLICATIONS
In this thesis, we studied the neurobiology of alternative conceptualizations of child psychiatry,
beyond the traditional DSM-framework. Traditional dichotomous categorizations do not do
justice to intermediate phenotypes. Imposing a cut-off always leads to the exclusion of a
group of sub-threshold-level affected children and may lead to misclassification. However,
the clinician, in order to make clinical decisions, often needs a categorical answer. Perversely,
the financial support for any psychiatric treatment may depend on it (Coghill and Sonuga-
Barke 2012). To the patient, the doctor and to society, the notion of a continuous structure
of autistic impairment comes with conceptual consequences. Kendell and Jablensky argued
that diagnostic categories are valid only if they can be viewed as truly discrete entities with
natural boundaries (Kendell and Jablensky 2003). With the phenotypical and neurobiological
boundaries of autism blurring, the question arises whether this is the case for ASD, and
whether we can define a meaningful cut-off. A commonly heard phrase nowadays describes
people as “on the spectrum”. However, in the context of a truly continuous distribution,
it becomes hard to define where this “spectrum” begins. Importantly, categorical and
dimensional approaches do not have to be mutually exclusive, as inclusive approaches can
take the best of both worlds. For instance, a recent study showed the existence of meaningful
sub-dimensions, within a continuously defined autistic phenotype (Grove et al. 2013). Personcentered
statistical identification of latent subgroups, where children are categorized based
on their overall, dimensional pattern of problem scores rather than severity of symptoms in
a single domain, can be useful method for neuroscientific research, as we showed in chapter
6 and 7. In the context of phenotypic heterogeneity, it may facilitate identification of more
specific correlates. However, it cannot be translated to clinical practice, as the application of
these methods requires statistical manipulation of data that is not feasible in clinical settings.
To the clinician, child psychiatry will always have to be dichotomous to some extent, as
many treatment decisions require a dichotomous answer. Severity cut-offs present the most
practical solution to obtain that. Accordingly, Kendell and Jablensky suggest that diagnoses
that do technically not have “validity” can still have “utility”. However, clinicians can also
benefit from embracing a continuous approach in child psychiatry, in better understanding
the full complexity of the clinical presentation of a child. Of note, subclinical symptoms may
cause disability and warrant treatment. Subclinical symptoms may also interact with other
diagnoses and affect the prognosis. In addition, continuous symptom severity measures can
help to monitor treatment effects.
In chapters 6 and 7, we searched for distinct cognitive correlates of internalizing and
externalizing correlates of behavior. This information facilitates a better understanding
of the underlying etiology. Considering our findings, internalizing symptoms may share
neurobiological pathways with language and memory impairments, while externalizing
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