Scoping the evidence for learning theories on PTSD in veterans

Abstract

Background: About 5–13% of Dutch veterans experience PTSD after being deployed (Eekhout et al. 2016). Although effective treatments for PTSD are available, response rates are lower amongst veterans (Watts et al., 2013). Learning theories have been postulated to underlie PTSD (Lissek and van Meurs, 2015). Here, we investigate the empirical evidence from veterans with PTSD for these theories. If we reveal which learning mechanisms are specifically altered in veterans with PTSD, feasible lab-models can be studied and future clinical decision making can be directed accordingly. Objective: Creating a systematic overview of empirical (clinical) evidence for learning models for PTSD in veterans. Method: A systematic search was performed in PubMed. Original studies written in English were included investigating veterans with PTSD and a learning theory. Articles were screened by AF and AK independently. Results: In total, 2167 articles were screened and 101 met our inclusion on the following theories: Amygdala Kindling (n = 30), Reduced Fear Inhibition (n = 17), Resistance to Extinction (n = 15), Stress Sensitization (n = 11), Overgeneralization (n = 7), Failure to Habituate (n = 5), Hyper-Conditionability (n = 3), Associative Learning Deficits (n = 3), Incubation (n = 1), TwoStage Learning (n = 1) and Failure to Inhibit Fear in the presence of safety cues (n = 0). Conclusions: Our systematic search shows evidence for Amygdala Kindling, Reduced Fear Inhibition, and Resistance to Extinction for veterans with PTSD. Other theories are less frequently investigated, revealing a research gap. The evidence supports that these mechanisms can be investigated in lab-models to develop interventions.