ریشه های فکر مکرر در نشخوار فکری: تفکیک سبک شناختی از اختلالات در کنترل بازدارندگی بر حافظه

Background and objectives Rumination is a major contributor to the maintenance of affective disorders and has been linked to memory control deficits. However, ruminators often report intentionally engaging in repetitive thought due to its perceived benefits. Deliberate re-processing may lead to the appearance of a memory control deficit that is better explained as a difference in cognitive style. Methods Ninety-six undergraduate students volunteered to take part in a direct-suppression variant of the Think/No-Think paradigm after which they completed self-report measures of rumination and the degree to which they deliberately re-processed the to-be-suppressed items. Results We demonstrate a relation between rumination and impaired suppression-induced forgetting. This relation is robust even when controlling for deliberate re-processing of the to-be-suppressed items, a behavior itself related to both rumination and suppression. Therefore, whereas conscious fixation on to-be-suppressed items reduced memory suppression, it did not fully account for the relation between rumination and memory suppression. Limitations The current experiment employed a retrospective measure of deliberate re-processing in the context of an unscreened university sample; future research might therefore generalize our findings using an online measure of deliberate re-processing or within a clinical population. Conclusions We provide evidence that deliberate re-processing accounts for some – but not all – of the relation between rumination and suppression-induced forgetting. The present findings, observed in a paradigm known to engage top-down inhibitory modulation of mnemonic processing, provide the most theoretically focused evidence to date for the existence of a memory control deficit in rumination.

Cognitive control plays an important role in maintaining good mental health. For example, it allows us to direct attention away from thoughts that might otherwise upset us, and focus instead on more productive activities. However, when such control fails, we may instead find ourselves doing the opposite: Dwelling on negative thoughts, sometimes with dire consequences (although, see Andrews & Thompson, 2009).1 The tendency to perseverate on past negative experiences has been termed ‘depressive rumination’ (Nolen-Hoeksema, 1991 and Nolen-Hoeksema, 2000) and has been found to predict the development of affective symptomatology such as suicidal ideation (e.g., Surrence, Miranda, Marroquin, & Chan, 2009). More recently, rumination has been recognized as a transdiagnostic process that is present in many anxiety and affective disorders (Ehring et al., 2011 and McLaughlin and Nolen-Hoeksema, 2011), and appears to have a causal impact on the development of intrusive memories (Ball & Brewin, 2012). For this reason, it is perhaps no surprise that there has been growing interest in the cognitive and biological factors that predispose certain individuals towards rumination (for reviews, see Joormann, 2010 and Whitmer and Gotlib, 2013). In recent years, rumination has been linked to meta-cognitive beliefs concerning the utility and uncontrollability of repetitive thought (Papageorgiou & Wells, 2003). Whereas the belief that rumination is an adaptive cognitive strategy predicts the onset of rumination, the belief that rumination is uncontrollable or related to poor interpersonal or social outcomes has been found to mediate the relationship between rumination and depressive symptomatology. Perhaps lending credibility to beliefs concerning its uncontrollability, rumination has also been associated with executive dysfunction across a range of cognitive tasks, even after controlling for depression (e.g., De Lissnyder et al., 2011, Joormann, 2005, Nolen-Hoeksema et al., 2008 and Whitmer and Banich, 2007). For example, rumination has been found to predict impairments in the ability to disengage attention in an antisaccade task (De Lissnyder et al., 2011) and also in the ability to inhibit previous task sets in a task-switching paradigm using either emotional or non-emotional materials (De Lissnyder et al., 2010 and Whitmer and Banich, 2007). Such dysfunction has been shown to precede (as opposed to follow) the onset of rumination, suggesting a critical role in the emergence of this behaviour (De Lissnyder et al., 2012 and Whitmer and Gotlib, 2012). In fact, some theorists have argued that it is a general impairment in the ability to disengage attention from distracting or unwanted information that predisposes certain individuals towards ruminating in the first place (Koster, De Lissnyder, Derakshan, & De Raedt, 2011). Accordingly, the ability to focus on relevant information and suppress irrelevant information – either internally or externally – is critical in avoiding repetitive thought cycles, and “… individuals who are characterized by a difficulty to exercise attentional control in response to negative thoughts are likely to experience persistent rumination” (p. 139, Koster et al., 2011). Despite some accounts (e.g., Joormann, 2010), these impairments do not appear to be limited to emotional material – at least in the absence of depression (Whitmer & Gotlib, 2013).

The present findings provide some of the strongest evidence to date that rumination is associated with diminished inhibitory control over memory and that this impairment could underlie the core deficit. Our findings are particularly diagnostic because they are the first to control for differences in cognitive style between ruminators and non-ruminators, to demonstrate this relation in the context of non-emotional stimuli and to use direct suppression instructions that recent neuroimaging evidence suggests better isolate top-down inhibitory modulation of mnemonic processing (e.g., Benoit & Anderson, 2012). We believe that our findings support a memory control deficit associated with rumination that is dissociable from a general cognitive style that might likewise encourage repetitive thought. An important implication is that clinical interventions applied to ruminative populations should address both the maladaptive beliefs concerning repetitive thought and also the apparent inhibitory deficits that might complicate the suppression of those thoughts once rumination has begun. For example, a recent intervention aimed specifically at rumination in treatment-resistant depression included elements designed to improve attentional control as well as modifying meta-cognitive beliefs (Wells et al., 2012). Other promising approaches that have brought about significant reductions in depressive rumination have sought to modify the intrusion of unwanted memories by having depressed patients vividly imagine positive competitor memories, and if necessary re-scripting negative memories (Brewin et al., 2009 and Ekkers et al., 2011). At present it is not known if these interventions operate by enhancing general inhibitory control. Designing more specific interventions targeted at inhibitory processes, as well as identifying possible genetic contributions to inhibitory control, holds promise for maximizing the effectiveness of therapies for rumination.