by Rebecca Webb, Centre for Maternal & Child Health Research, City University London
While birth can be a positive experience for many women, up to one third of women describe their birth as traumatic (Olde et al, 2006). The role of cognitive processes and biases in postpartum PTSD is unclear. Ehlers and Clark (2000) suggest that PTSD develops through an interaction between previous experiences, beliefs and coping strategies and the actual event itself. This interaction influences the ongoing appraisal of the event, which creates and maintains the PTSD symptoms. There is some support for this theory in postpartum PTSD (Ford et al 2010).
One of the cognitive processes thought to influence the development of PTSD is selective attention towards threatening stimuli. This phenomenon can be measured in a number of ways but is commonly assessed using an emotional Stroop task. In the classic Stroop task, participants name the colour of words presented to them. Some of the words are consistent with their colour e.g. ‘Blue’, whilst others are not (‘Blue’). Participants are slower to name the inconsistent words. This paradigm has subsequently been used to compare response times to colour-naming of emotional words compared to neutral words, with emotional words exhibiting slower response times. Cisler et al., (2011) conducted a meta-analysis of the emotional Stroop paradigm undertaken with participants with PTSD. They found that people with PTSD were slower to name the colour of trauma related words, which is thought to represent captured attention, i.e. the trauma related word held the attention of the participant, slowing them down. The results from these studies suggest PTSD is associated with hyper-vigilance towards threat-relevant information. This, however, may lead to the person avoiding threat, which can maintain anxiety as the individual never gains counter information about the threat.
It is not clear whether this attentional bias is the same in birth-related PTSD. Only one study has used an emotional Stroop paradigm to investigate whether women with birth-related PTSD have similar attentional biases to threat related stimuli as those with PTSD arising from non-childbirth-related events. Dale-Hewitt et al, (2012) conducted a labour related emotional Stroop task with women who were either categorised as having PTSD, or having experienced their birth as traumatic on one of three dimensions of PTSD (avoidance, intrusion, hyper-vigilance). Contrary to the evidence from non-birth-related PTSD, women who scored high on avoidance and intrusion, but not hyper-vigilance, were faster at performing the emotional Stroop task. The authors argue that the mechanisms in birth-related PTSD may differ from non-birth-related PTSD because the baby is constantly there in the form of a reminder. Therefore, rather than avoiding the trauma, as in other event related PTSD, labour related words may be continuously activated in memory (Foa et al, 1989), meaning the mothers need less time to identify these words as threatening and can apply ignoring strategies more quickly.
Dale-Hewitt et al’s findings suggest that attentional biases in birth-related PTSD and other event related PTSD may differ in terms of causal and maintaining factors. However, the lack of birth-related PTSD Stroop data makes it hard to draw any conclusions since it is impossible to generalise from a single study. Furthermore, the use of the Stroop paradigm to measure attentional biases in PTSD has been widely questioned. Kimble et al. (2004) found that only 44% of all studies (including unpublished dissertations) identified a Stroop effect for trauma related words in people with PTSD.
Despite the difficulty in drawing a conclusion from these results, one thing is clear; the cognitive processes behind birth-related PTSD need to be examined further. This may provide key clues to the aetiology and maintaining factors, which could therefore lead to more effective treatments in the future.