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<p>Major depressive disorder (MDD) and risk for its development are characterized by
reduced reactivity and flexibility to environmental demands. Frontal alpha asymmetry (FAA),
heart rate variability (HRV), and salivary cortisol reactivity are each well-established indicators of
regulation across neural, autonomic, and hypothalamic-pituitary-adrenal (HPA) physiological
systems, respectively. Growing literature suggests that each of these processes is dysregulated in
individuals with a history of MDD. However, patterns of dysregulation across these physiological
systems and relative MDD risk are unknown. Moreover, these physiological regulatory patterns
may extent beyond markers of MDD risk in adulthood to also capture the transmission of risk for
MDD from parent to offspring. The following series of five studies investigated the
pathophysiology of MDD and the permeability of risk across the lifespan. First, the pattern of
dysregulation across physiological indices—representing neural, autonomic, and HPA
functioning—in adults was examined with regard to depressive symptoms. Second, the
associations amongst infant FAA, HRV, and cortisol reactivity and maternal depressive symptoms
were assessed as potential early markers of depression risk. Third, mother-infant associations
across physiological indices were investigated to assess direct intergenerational transmission of
depression risk. Studies 4 and 5 further investigated pathophysiological functioning in mothers
and infants within the context of comorbid anxiety and current depressive symptomatology versus
lifetime MDD illness. Mothers and their 12-month-old infants (n = 35 dyads) completed resting-
state and stressor tasks to assess regulatory patterns across neural, autonomic, and HPA systems,
associations with MDD, and intergenerational transmission. In adults, results suggest that lifetime
history of MDD is significantly associated with blunted cortisol reactivity; FAA and high-
frequency HRV also demonstrated the same direction of associations. In infants, results
demonstrated that maternal depressive symptoms, particularly current symptoms, relate to blunted
physiological regulation in infants specifically for FAA and HRV indices. For mothers and infants,
there was support for the direct intergenerational transmission of FAA and HRV indices. These
intergenerational associations did not fully account for intergenerational risk of depression, as
maternal physiological regulation and maternal depression were found to each significantly predict
infant regulation as simultaneous predictors. Accounting for comorbid anxiety and examining
current symptoms versus lifetime illness were essential to investigating associations amongst physiological functioning and depression. These patterns in conjunction with the literature suggest
a developmental model to MDD pathophysiology that encompasses multiple theoretical
frameworks. Future research is necessary to clarify regulatory patterns across physiological
systems within individuals and across time with regard to MDD risk, onset, and course.</p></div></div></div>
| Identifer | oai:union.ndltd.org:purdue.edu/oai:figshare.com:article/12711878 |
| Date | 29 July 2020 |
| Creators | Kaylin E Hill (9167717) |
| Source Sets | Purdue University |
| Detected Language | English |
| Type | Text, Thesis |
| Rights | CC BY 4.0 |
| Relation | https://figshare.com/articles/thesis/Identifying_the_pathophysiology_of_depression_and_its_permeability_across_the_lifespan/12711878 |
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