Temporal and population dynamics of depressive symptoms : empirical and modeling approaches
Year: 2013
Type: dissertation
Abstract: Depression has been estimated to be the second largest cause of years lived with a disability, and much research on depressive symptoms exists. Despite this, basic research has not found natural taxa that would correspond to clinical diagnoses for depression. It is often assumed that a one-dimensional latent continuum underlies depressive symptoms, but empirical evidence does not support this idea either. Therefore, it has been suggested that depressive symptoms are part of a complex causal network that has not yet been adequately understood. This thesis aims to understand statistical variation and joint variation of individual depressive symptoms over time, the causal relationships between these symptoms, and their potentially adaptive evolutionary origins. The research material consists of the prospective Young Finns study that began in 1980 and included 3596 participants, the 10317-participant Wisconsin Longitudinal study, and mathematical models for the evolution of cooperation. First, temporal trajectories of a depressive-symptom sum was modeled with a stochastic differential equation model which results in a more empirically justified approach than typical latent-trait models, allowing causal roles for individual symptoms rather than viewing them as passive reflections. Regarding individual symptoms, it was shown that body-image dissatisfaction was the most temporally stable symptom, and strongly associated with chronically elevated dysphoria over a 16 year follow-up. In contrast, symptoms related to sleep and tiredness were the least stable, and novel methods based on non-Gaussian distributions suggested that sleep problems cause other depressive symptoms. Finally, combining the bargaining models of depression with mathematical models for the evolution of cooperation showed that, in theory, evolution should favor the emergence of depressive symptoms in natural populations, as they promote fitness-enhancing cooperation by rendering defection from joint enterprises less tempting. Overall, instead of a single disorder, depressive symptoms may reflect multiple processes, some of them being adaptive instead of dysfunctional.
Source: Työväentutkimus Vuosikirja
Author: Tom Rosenström
Language: English
Subfield: Experimental and Cognitive Psychology
Field: Psychology
Domain: Social Sciences
Open Access status: green
OpenAlex ID: W2726340041