Concerns about medications mediate the association of posttraumatic stress disorder with adherence to medication in stroke survivors

Though posttraumatic stress disorder (PTSD) was originally understood as a disorder primarily associated with combat, PTSD is increasingly recognized as a common psychological consequence of life-threatening medical events such as acute coronary syndrome (ACS), (Edmondson et al., 2012) cancer diagnosis (Andrykowski, Cordova, Studts, & Miller, 1998), and stroke (Kronish, Edmondson, Goldfinger, Fei, & Horowitz, 2012). In a meta-analysis of 24 studies, the prevalence of PTSD due to ACS was estimated at 12% (Edmondson, Richardson, et al., 2012), and research suggests that PTSD due to stroke may be even more common (Kronish, Edmondson, Goldfinger, et al., 2012). In addition to directly causing psychological symptoms, PTSD triggered by medical events may also put patients at increased risk for a worse prognosis from their underlying medical illness. For example, ACS-induced PTSD is associated with a doubling of risk for cardiac event recurrence and mortality up to 3 years after the index event (Edmondson, Richardson, et al., 2012; Edmondson, Rieckmann, et al., 2011; Shemesh et al., 2004; von Kanel et al., 2011). It is not known whether stroke-induced PTSD is associated with adverse medical outcomes. While a number of biological mechanisms, such as increased blood pressure (Muraoka, Carlson, & Chemtob, 1998), endothelial dysfunction (von Kanel et al., 2008) and systemic inflammation (von Kanel et al., 2010) have been proposed to explain the association between PTSD and recurrent cardiovascular events in ACS patients, behavioral mechanisms (Newman et al., 2011) such as medication nonadherence are also possible mechanisms (Rahiman et al., 2008; Shemesh, et al., 2004). In survivors of strokes and transient ischemic attacks (TIAs), adherence to risk-reducing medications, including antiplatelet agents, antihypertensive agents, and statins, is especially important for preventing subsequent strokes (Rothwell, Algra, & Amarenco, 2011). However, in the Adherence eValuation After Ischemic Stroke Longitudinal (AVAIL) registry, a large prospective cohort of stroke survivors, 14% of participants self-reported not adhering to medication regimens (Bushnell et al., 2011). To date, most studies have focused on demographic and system-level predictors of nonadherence, many of which may be intractable (Bushnell et al., 2010; Tuhrim et al., 2008). We previously reported that 40% of our sample of predominantly low-income and minority long-term stroke survivors self-reported poor adherence to medication and that 75% reported at least some PTSD symptoms, with 18% of the participants reporting symptoms above the cutoff point for likely PTSD diagnosis. Furthermore, we found that those with the most severe PTSD symptoms were nearly 3 times as likely as those without PTSD symptoms to be nonadherent to medications (Kronish, Edmondson, Goldfinger, et al., 2012). Social cognitive theories of health behavior such as the health belief model (Rosenstock, 1974) and self-regulation models (Hall & Fong, 2007; Leventhal, Brissette, & Leventhal, 2003; Maes & Gebhardt, 2000) suggest that individuals undertake a cost-benefit analysis when deciding to follow medical treatment; this process involves considering whether the perceived need for treatment outweighs concerns about treatment. Though they did not measure PTSD or other potential influences on concerns about medications, a recent study with 180 stroke survivors found that concerns about medications were among the strongest predictors of stroke survivors’ nonadherence to medications both cross-sectionally and prospectively at 1 year poststroke (O’Carroll et al., 2011). One hypothesis to explain the association between PTSD and nonadherence to medication is that stroke survivors with PTSD have increased concerns about medications, potentially shifting the balance between perceived need and concerns, with the result of decreased adherence. This explanation is plausible, as 2 major categories of PTSD symptoms—hypervigilance and avoidance—may lead those with PTSD as a result of a medical event to perceive their medications as threatening reminders of the event (Shemesh et al., 2001; Shemesh, et al., 2004). While it is possible that other explanations may play a role in the association between PTSD and medication nonadherence, such as altered risk perception in patients with PTSD (Edmondson, Shaffer, Denton, Shimbo, & Clemow, 2012) or general avoidance of threatening health-related stimuli (Newman, et al., 2011), the hypervigilance and avoidance hypothesis is supported by findings on PTSD and medication adherence in HIV patients (Delahanty, Bogart, & Figler, 2004). Catz et al explained the finding that symptoms of HIV-induced PTSD were associated with skipping highly active antiretroviral therapy by noting that the most frequently cited reason for nonadherence to HIV medications was that “medications remind me that I am HIV positive” (Catz, Kelly, Bogart, Benotsch, & McAuliffe, 2000; Chernoff, 2007). Evidence for the hypervigilance and avoidance hypothesis would be a finding that greater concerns about potential threats associated with medications and greater general worry about medications, but not decreased awareness that such medications are medically necessary, mediate the association between PTSD and medication nonadherence. Our aims were to explore the association between beliefs about medications and PTSD in survivors of strokes and TIAs and to determine whether beliefs mediated the association we previously found between PTSD and nonadherence to medication. We hypothesized that greater concerns about medications, but not lower perceptions of the necessity of medications, mediate the association between PTSD symptoms and nonadherence to medication in a large sample of stroke survivors.