ASD and ADHD are highly diverse neurodevelopmental conditions with significant
co-occurrence-some estimates suggest rates as high as 78% (Leitner, 2014). However,
research often excludes neurodiverse children with co-occurring conditions or subclinical
symptoms, making many study populations unrepresentative of real-world scenarios.
Currently, there are no fully safe and effective treatments for ASD or ADHD symptoms
(Groom & Cortese, 2022; Oono et al., 2013; Williams et al., 2010), which leads many
parents to explore complementary treatments, such as omega-3 supplements, among the most
popular options (Green et al., 2006; Sinha & Efron, 2005). Omega-3s, essential for brain
development and function, are often deficient in UK children, particularly those with
behavioral or learning difficulties (Montgomery et al., 2014).
Some clinical trials suggest that omega-3 supplementation, specifically EPA
(eicosapentaenoic acid) and DHA (docosahexaenoic acid), can improve symptoms such as
sleep disturbances, hyperactivity-impulsivity, and inattention in children with ADHD
and/or ASD-like difficulties (Bent et al., 2014; Richardson & Montgomery, 2005). However,
findings across studies have been inconsistent, with systematic reviews and meta-analyses
yielding varied conclusions (Abdullah et al., 2019; Bloch & Qawasmi, 2011; Gillies et
al., 2012). These discrepancies likely arise from variations in study populations,
treatments, outcome measures, and trial designs.
A key limitation is the traditional approach of treating ASD and ADHD as distinct
diagnostic categories, adhering to the "latent variable" model in psychiatry, which
assumes that symptoms reflect an underlying disorder. This approach has two major flaws:
(a) it encourages studying groups presumed homogeneous based on diagnosis, ignoring
within-group variability and symptom overlap across disorders, and (b) it directs
treatment toward presumed underlying diseases rather than focusing on specific symptoms
and their interactions. This "one-size-fits-all" model may contribute to the inconsistent
findings in omega-3 research for neurodevelopmental conditions.
In contrast, network science offers a more dynamic approach, viewing disorders as
networks of interacting symptoms rather than symptoms being caused by a single underlying
disorder. This approach enables visualization of symptom networks, including complex
connections that explain symptom overlap. For instance, "bridge" symptoms link different
disorder domains, while "central" symptoms, which are highly connected, drive other
symptoms and may be ideal treatment targets. Monitoring symptom networks during treatment
can help identify individuals more likely to benefit based on unique symptom profiles
(Bringmann et al., 2022; Bekhuis et al., 2018).
To date, the network approach has not been used to explore how omega-3 supplementation
affects ASD and ADHD symptoms. Our study aims to apply this method to: (a) better
understand the shared features of ADHD and ASD by identifying "bridge symptoms" and
examining whether omega-3 supplementation influences these symptoms; (b) identify
phenotypes that cross diagnostic boundaries and might benefit from omega-3
supplementation; and (c) promote a more inclusive approach to treating ADHD/ASD symptoms
by focusing on symptom profiles rather than diagnostic labels.
We hypothesize that sleep disturbances and emotional dysregulation will act as "bridge
nodes" that connect ADHD and ASD, given their presence across multiple disorders. Based
on prior studies (Montgomery et al., 2014; Richardson, 2006; Richardson & Montgomery,
2005), we also propose that omega-3 supplementation will directly improve a cluster of
symptoms related to sleep, emotional regulation, and hyperactivity-impulsivity. Any
additional benefits are expected to be indirect, resulting from improvements in these key
symptoms.