Posttraumatic stress disorder (PTSD) is 3-5 times more prevalent in individuals with bulimia nervosa (BN) than those without (Dansky et al., 1997). However, the relationship between PTSD and BN–in particular, how PTSD might affect or moderate bulimic symptoms–remains largely unexplored. In a recent study, Trisha Karr and colleagues followed 119 women (20 with PTSD and BN, and 99 with BN only) for a 2 week period to investigate whether participants with comorbid PTSD + BN differed from those with BN only on the:
- Levels of negative affect (negative emotional state/mood) and affect variability (fluctuation between negative and positive states)
- Frequency of bulimic behaviours
- Relationship between emotional states (negative or positive affect) and bulimic behaviours
They used the ecological momentary assessment (EMA) tool to track behaviours and emotional states close to when they occur. I’ve blogged about a study using EMA before (‘What’s The Point of Bingeing/Purging? And Why Can’t You Just Stop?’), but briefly,
EMA techniques provide methods by which a research participant can report on symptoms, affect, behaviour and cognitions close in time to experience, and these reports are obtained many times over the course of a study.
Participants were prompted to recording their mood and behaviour(s) at 6 semi-random times each day, over a two-week period. The authors then looked at the mood (negative and positive affect) before and after bingeing and/or purging behaviours. (See figures in this post to see what I mean.)
- Mean age: 29 for PTSD + BN group, 24 for BN only
- No differences on education level or BMI
- PTSD + BN group was more likely to be married
Prevalence of other psychiatric disorders:
- Mood disorders: 70% for PTSD + BN, 52% for BN only
- Substance use disorders: 15% for PTSD + BN, 16.5% for BN only
- Anxiety disorders: 70% for PTSD + BN, 40% for BN only (statistically significant)
In their analyses, the authors controlled for the other comorbid conditions (mood disorders, substance use, other anxiety disorders). I’ve summarized the main findings of the study below:
SUMMARY OF MAIN RESULTS
- Individuals in the PTSD + BN group reported higher levels of negative affect than those with BN only.
- The authors hypothesize that this might be due to increased “sensitivity to stimuli involving perceptions of threat, rejection, or criticism.”
- Individuals in the PTSD + BN group reported higher frequencies of binge eating and purging behaviours than those in the BN only group. This is similar to other studies comparing BN women with and without a history of childhood sexual abuse, although there have been studies which found no association between trauma or abuse history and frequency of eating disorder behaviours.
- The authors hypothesize that “Perhaps the presence of diagnosable PTSD, examined in the present study, is a more potent predictor of bulimic severity than a history of child trauma and reflects the affective dysregulation that accompanies PTSD but does not always accompany the experience of trauma or abuse.
- Negative affect increased and positive affect decreased prior to binge eating for both the PTSD + BN and BN only groups. Conversely, negative affect decreased and positive affect increased after binge eating for both groups. There were no differences between groups when it came to the relationship between affect and binge eating. These findings are similar to the ones I’ve blogged about previously.
- Interestingly, there was a difference when it came to purging. Just like for binge eating, negative affect increased and positive affect decreased prior to purging. Following purging, negative affect decreased and positive affect increased. But, negative affect increased at a faster rate before purging and decreased at a faster rate after purging for the PTSD + BN group versus the BN only group. The same pattern of a faster decrease and increase was observed for positive affect as well.
- These findings suggest that PTSD modifies the relationship between negative and positive emotional states and purging in women with bulimia nervosa.
What do these findings, particularly the latter, mean? Well, it is hard to say. All that we know is that in this sample, women with BN and PTSD experienced more rapid increases in negative emotional states prior to purging and more rapid decreases following purging (and opposite pattern for positive states). It is interesting that this did not hold up for binge eating episodes, though.
Are these findings generalize? Again, it is hard to say. The PTSD + BN group, with only 20 participants, was 5 times smaller than the BN only group. That’s a small sample, and it is hard to say whether in a similar study with 10 times the numbers, the differences will become more significant or less.
Unfortunately, the authors did not go into detail discussing the possible implications of the findings with respect to the third question. I do not have much background in PTSD, so it is difficult for me to comment, but my first thought is that this might suggest that purging is more negative reinforcing for individuals with comorbid PTSD than those with BN only. (Negative reinforcement is the removal of an aversive stimulus.)
Taken as a whole, these data suggest that individuals with comorbid PTSD and BN experience more negative emotional states (higher daily level of negative affect) and exhibit a greater frequency of bulimic behaviours than their BN only counterparts. In addition, purging may be regulating emotions differently (or perhaps more strongly?) in individuals with comorbid PTSD + BN than BN only.
If these findings do hold up, I wonder what implications they might have for treatment of patients with comorbid PTSD and BN.
Readers, if you have experienced comorbid PTSD and BN (or any other ED), how did the PTSD affect your ED or ED recovery? Were (or are) there things that help one (PTSD or BN) at the expense of the other, or does improving PTSD symptoms concurrently improves BN symptoms, too?
Karr, T., Crosby, R., Cao, L., Engel, S., Mitchell, J., Simonich, H., & Wonderlich, S. (2013). Posttraumatic stress disorder as a moderator of the association between negative affect and bulimic symptoms: an ecological momentary assessment study Comprehensive Psychiatry, 54 (1), 61-69 DOI: 10.1016/j.comppsych.2012.05.011