Posttraumatic stress disorder (PTSD) is a disabling mental illness and substantial public health burden: 6.8% of American adults will be diagnosed with PTSD in their lifetimes (Kessler et al. 2005
). PTSD is characterized by symptoms of re-experiencing, avoidance and emotional numbing, hyperarousal, and significant functional impairment (criteria B–D, F); these symptoms last at least 1 month (criterion E) and are causally linked to the experience of a traumatic stressor (American Psychiatric Association 1994
). The Diagnostic and Statistical Manual of Mental Disorders IV
(DSM-IV) defines a traumatic stressor as any event directly experienced, witnessed, or confronted by an individual that involves serious threat or injury to the individual or others (criterion A1), and this event elicits intense fear, helplessness, or horror (criterion A2) (American Psychiatric Association 1994
). Although 90% of individuals may experience a potentially traumatic event in their lifetimes, only 13.0% of women and 6.2% of men exposed to these events subsequently develop PTSD (Breslau et al. 1998
). Research demonstrates that the conditional risk for PTSD following severe traumas, such as rape (49.0%) and assaultive violence (20.9%), is higher than for events that are more widely prevalent in the population but do not generally provoke such intense emotional reactions. For example, the conditional risk for PTSD after learning about a traumatic event experienced by a loved one is only 3.6% (Breslau et al. 1998
A large body of research demonstrates that both trauma and PTSD are positively associated with affective, anxiety, and substance abuse disorders (Kessler et al. 1995
; Pietrzak et al. 2011
). However, there has been little research examining the comorbid relationship between PTSD and premenstrual dysphoric disorder (PMDD), a disorder prevalent among 3–8% of American women (Halbreich et al. 2003
). Although existing literature suggests that trauma and PTSD are correlated with PMDD, it is unclear whether this relationship is driven by the trauma that may lead to PTSD or if PTSD is uniquely associated with PMDD. Thus, a closer examination of the independent associations between trauma and PTSD and PMDD is warranted.
Premenstrual symptoms occur cyclically in the week prior to the onset of menses and encompass both affective and somatic changes. Premenstrual symptoms cause only minor to moderate impairment, whereas symptoms of PMDD are of such intensity that a woman’s ability to function normally at work, in the home, and in interpersonal interactions is disrupted (American Psychiatric Association 2000
). Using Census 2000 data, Halbreich and colleagues estimated the disability adjusted life years (DALYs) attributable to PMDD in the USA to be 14.5 million (Halbreich, et al. 2003
). To put this figure into context, the Global Burden of Disease study estimated the DALYs associated with all neuropsychiatric conditions in the USA (calculation excludes PMDD) was 4.8 million in 2004 (WHO 2009
The psychophysiological mechanisms linking PMDD and PTSD have not been investigated. However, a number of studies have found evidence of autonomic nervous system dysregulation in both patients with PMDD and patients with PTSD. For example, both PTSD and PMDD have been associated with low levels of baseline high-frequency heart rate variability, an indication of resting hyperarousal (Landén et al. 2004
; Matsumoto et al. 2007
; Pole 2007
). However, it is unclear whether the autonomic nervous system dysregulation characteristic of PTSD is a risk factor for PMDD, if PMDD is a risk factor for development of PTSD after a traumatic event, or if the dysregulation of the autonomic nervous system reflects a shared vulnerability to PTSD and PMDD. It is beyond the scope of the present study to fully investigate these potential pathways. However, these findings provide a psychophysiological basis for further epidemiological investigation of the relationship between trauma, PTSD, and PMDD and premenstrual symptoms.
Although PTSD and trauma exposure have been linked to premenstrual symptoms in a number of studies (Golding et al. 2000
; Koci and Strickland 2007
), only three studies have explicitly examined the association between PTSD and PMDD. All three studies utilized data from a cohort of 1,251 German women (age 14–24 at baseline) who were evaluated prospectively from 1995 to 1999. With these data, investigators demonstrated that baseline PTSD was significantly associated with incident PMDD, independently of age (Perkonigg et al. 2004
; Wittchen et al. 2002
). Although the results are provocative, several methodological limitations weaken the results’ generalizability and necessitate further research. First, cohort members were relatively homogenous in terms of age, race, marital status, and socioeconomic status. Consequently, the findings from these studies may not apply to more diverse populations. Second, the results of these studies may be dated and not applicable to the current population of women, as the incidence of trauma and women’s awareness of PMDD may have changed since these data were collected. A third limitation was the restricted age range of the study cohort, which did not adequately represent the population of women at risk for PMDD (all women of childbearing age). Importantly, PMDD does not typically develop until women reach their mid-20s, and it becomes increasingly prevalent and more severe with age (Stein et al. 2006
). Given the young age of the cohort and the brief period of follow-up, the researchers’ ability to capture later-onset cases was substantially reduced among this cohort. Similarly, exposure to potentially traumatic events was lower in this young cohort (only 8.2% baseline prevalence) (Perkonigg et al. 2004
) than would be observed in the general population of women. For instance, the prevalence of potentially traumatic events among American women aged 20–59 in a nationally representative survey was 80.32% (Grant 2005
A fourth limitation of prior work was the analytic approach, in which investigators failed to present the unique effects of trauma and PTSD on PMDD. In two of the three studies, investigators included PTSD in a multivariate model but did not limit their sample to women exposed to potentially traumatic events (Wittchen et al. 2002
). Thus, the true association between PTSD (as a phenomenon distinct from trauma) and PMDD was likely underestimated in this analysis. In the third study, investigators included indicator variables for PTSD status and trauma history in a multivariate model (Perkonigg et al. 2004
). This approach is problematic because trauma exposure is a necessary (but not sufficient) cause of PTSD, and thus, these factors are not truly independent. Consequently, PTSD and trauma should not enter a multivariable model as two separate indicator variables. To more accurately determine the independent effects of potentially traumatic events and PTSD, researchers have most often characterized exposure as a three-level categorical variable: exposure to trauma without PTSD, exposure to trauma with PTSD, and no exposure to trauma (Löwe et al. 2010
; Sledjeski et al. 2008
). Investigators have also addressed this issue by restricting their sample to survivors of trauma and including an indicator of PTSD status in their multivariate model (Lawler et al. 2005
). We utilized both approaches in the current study.
It was also unclear in these studies whether the effect of PTSD would remain significantly associated with PMDD among trauma survivors if there was adequate statistical control for characteristics of participants’ trauma history. Since evidence demonstrates that persons with more numerous and severe experiences of trauma are more likely to develop PTSD (Breslau et al. 1999
; Kilpatrick and Saunders 1999
; Resnick et al. 1993
), trauma characteristics may partially or fully explain the observed association between PTSD and PMDD among trauma survivors.
In the single study of the German cohort that featured simultaneous control for PTSD and trauma exposure, the trauma variable indicated the presence of a history of trauma exposure, rather than the number or severity of exposures (Perkonigg et al. 2004
). Nevertheless, while PTSD was significantly associated with PMDD in age-adjusted analysis, the addition of trauma exposure and other covariates (subthreshold PMDD, psychiatric comorbidity, life stress, and self-competence) rendered this relationship non-significant. Since this was not a stepwise analysis (nor was the population limited to survivors of trauma only), the authors could not determine whether it was the effect of trauma exposure or the effects of other model covariates that attenuated the previously significant association between baseline PTSD and incident PMDD. Thus, additional, more nuanced research is needed to determine whether PTSD remains significantly associated with PMDD following statistical control for trauma severity.
The goal of the current study was to untangle the relationship between trauma, PTSD, and PMDD among a larger and more diverse sample of American women, thereby extending the findings of prior studies of PMDD. We included a three-level categorical variable to characterize exposure to trauma and PTSD and investigated the number and severity of traumatic events as possible explanatory factors in the relationship between PTSD and PMDD. Finally, we examined these exposures in relation to the prevalence of premenstrual symptoms, in addition to PMDD.
We predicted that there would be a graded relationship between trauma, PTSD, and PMDD status, with trauma survivors and persons who develop PTSD in the aftermath of trauma having elevated odds for PMDD and premenstrual symptoms compared to the reference group (no trauma exposure). In a second analysis restricted to survivors of trauma, we explored whether the effect of PTSD remained significantly associated with PMDD and premenstrual symptoms after controlling for the severity and number of traumatic experiences reported by participants. On the basis of prior literature demonstrating that PTSD is strongly associated with chronic illness (Schnurr et al. 2007
) and psychopathology (Brady, et al. 2000
) independently of exposure to trauma, we hypothesized that PTSD would remain significantly associated with PMDD after trauma characteristics were included in our multivariate model. The effect of PTSD would be attenuated, however, suggesting that trauma characteristics partially explained the association between PTSD and PMDD. Because prior evidence has linked trauma exposure to premenstrual symptoms, we hypothesized that if a significant association between PTSD and premenstrual symptoms were observed, it would be fully accounted for by characteristics of trauma.