Epilogue: continuing points of contention in the recovered memory debate

Successfully controlling intrusive memories is harder when control must be sustained

After unpleasant events, people often experience intrusive memories that undermine their peace of mind. In response, they often suppress these unwanted memories from awareness. Such efforts may fail, however, when inhibitory control demands are high due to the need to sustain control, or when fatigue compromises inhibitory capacity. Here we examined how sustained inhibitory demand affected intrusive memories in the Think/No-Think paradigm. To isolate intrusions, participants reported, trial-by-trial, whether their preceding attempt to suppress retrieval had triggered retrieval of the memory they intended to suppress. Such counter-intentional retrievals provide a laboratory model of the sort of involuntary retrieval that may underlie intrusive memories. Using this method, we found that longer duration trials increased the probability of an intrusion. Moreover, on later No-Think trials, control over intrusions suddenly declined, with longer trial durations triggering more relapses of items that had been previously been purged. Thus, the challenges of controlling retrieval appear to cause a decline in control over time, due to a change in state, such as fatigue. These findings raise the possibility that characteristics often true of people with psychiatric disorders - such as compromised sleep, and increased demand on control - may contribute to difficulties in suppressing intrusive memories.

Onset of common mental disorders and suicidal behavior following women's first exposure to gender based violence: a retrospective, population-based study

BACKGROUND

Women exposed to gender-based violence (GBV) experience a high rate of common mental disorders and suicidal behaviour ("mental disturbance"). Little is known however about the timing of onset of mental disturbance following first exposure to GBV amongst women with no prior mental disorder.

METHODS

The analysis was undertaken on the Australian National Mental Health and Wellbeing Survey dataset (N = 8841). We assessed lifetime prevalence and first onset of common mental disorder and suicidal behaviour (mental disturbance) and exposure to GBV and its first occurrence based on the Composite International Diagnostic Interview Version 3 (WMH-CIDI 3.0). We used the Kaplan-Meier method to derive cumulative incident curves for first onset mental disturbance. The two derived subgroups were women who experienced GBV without prior mental disturbance; and women never exposed to GBV stratified to match the former group on age and socio-economic status.

RESULTS

For women with no prior mental disorder, the cumulative incidence curves showed a high incidence of all mental disturbances following first GBV, compared to women without exposure to GBV (all log rank tests <0.0001). Nearly two fifths (37%) of any lifetime mental disturbance had onset in the year following first GBV in women exposed to abuse. For these women, over half (57%) of cases of lifetime PTSD had onset in the same time interval. For GBV exposed women, half of all cases of mental disturbance (54%) and two thirds of cases of PTSD (66.9%) had onset in the five years following first abuse. In contrast, there was a low prevalence of onset of mental disturbance in the comparable imputed time to event period for women never exposed to GBV (for any mental disturbance, 1% in the first year, 12% in five years; for PTSD 3% in the first year, 7% in five years).

CONCLUSIONS

Amongst women without prior mental disturbance, common mental disorders and suicidal behaviour have a high rate of onset in the one and five year intervals following exposure to GBV. There is a particularly high incidence of PTSD in the first year following GBV.

Emotional and non-emotional memories are suppressible under direct suppression instructions

Research on retrieval suppression has produced varying results concerning whether negatively valenced memories are more or less suppressible than neutral memories. This variability may arise if, across studies, participants adopt different approaches to memory control. Cognitive and neurobiological research points to two mechanisms that achieve retrieval suppression: thought-substitution and direct suppression (Benoit & Anderson, 2012; Bergström, de Fockert, & Richardson-Klavehn, 2009). Using the Think/No-think paradigm, this study examined whether participants can inhibit neutral and negatively valenced memories, using a uniform direct suppression strategy. Importantly, when strategy was controlled, negative and neutral items were comparably inhibited. Participants reported high compliance with direct suppression instructions, and success at controlling awareness predicted forgetting. These findings provide the first evidence that direct suppression can impair negatively valenced events, and suggest that variability in forgetting negative memories in prior studies is unlikely to arise from difficulty using direct suppression to control emotionally negative experiences.