Similar studies

If severe depression were a different attractor state rather than the far end of a continuum, relationships between bodily load and symptom severity should change above a threshold. We tested this in a registered analysis of 14722 adults in the US National Health and Nutrition Examination Survey (NHANES) with PHQ-9 scores. Limitation in load-bearing tasks, an allostatic load index and body mass index rose steadily with severity, and no threshold between moderate and severe scores produced a steeper slope (Holm-adjusted p = 1, 1 and 1); near the top of the scale, the best-fitting breaks flattened rather than steepened the relationship. Height, a negative control, showed no break. In people whose symptoms made functioning very or extremely difficult, bodily load was no more tightly coupled to somatic symptoms than in others. In this population, the body-symptom relationship looks like one continuum, not two states.

• Published, Reproduced, Reviewed.Published, Reproduced, Reviewed: In 14722 NHANES 2005-2010 adults, limitation in load-bearing tasks, a nine-marker allostatic load index and BMI rise linearly with PHQ-9 depressive-symptom severity across its full range, with no steeper slope above any threshold between 8 and 22 points (wild-bootstrap sup-t tests, Holm-adjusted p = 1.0, 1.0 and 1.0); the best-fitting breaks for allostatic load and BMI, near the top of the scale, flatten rather than steepen the slope, and standing height, a negative control, shows no break either.
• Published, Reproduced, Reviewed.Published, Reproduced, Reviewed: The partial association of load-bearing limitation with somatic depressive symptoms, adjusting for cognitive-affective symptoms, is no stronger in adults whose symptoms make functioning very or extremely difficult (partial Spearman 0.1607, n = 454) than in other adults with symptoms (0.1746; difference -0.0139, 95% CI -0.1036 to 0.0773).

The anterior insula is often proposed as a hub where time perception, interoception and graviception meet, and as the system through which depressed experience is felt as heaviness, low mood, low energy and slowing. Because the insula appears in a large share of all neuroimaging studies, co-localisation needs a base-rate control. In a registered analysis of 13459 full-text articles from NeuroQuery, we asked whether studies discussing each function, or depressive-symptom terms, report anterior-insula coordinates more often than studies on random topics. Interoception studies did (association z 10.259), but equally in the posterior insula; time perception (z {{R1.terms.time perception.anterior_insula.z}}) and vestibular studies (z -0.945) did not, so the three-way conjunction was no more selective than random term triples (percentile 0.5456). Symptom terms were not selective either (percentile 0.7064). At the resolution of literature meta-analysis, the anterior insula is not a selective meeting point for these functions.

• Published, Reproduced, Reviewed.Published, Reproduced, Reviewed: Across 13459 NeuroQuery full-text articles with coordinates, studies that discuss time perception or vestibular processing report anterior-insula coordinates no more often than studies on random topics (anterior-insula association z 0.424 and -0.945; percentiles 0.4959 and 0.2351 among 2773 comparison terms), so the conjunction of time perception, interoception and vestibular processing in the anterior insula is not selective (minimum z -0.945, percentile 0.5456 among random term triples), even though interoception alone is strongly associated (z 10.259).