خاطرات مزاحم و افسردگی در بیماران مبتلا به سرطان

Abstract Matched samples of depressed and nondepressed cancer patients were interviewed about past life events, particularly experiences of death and illness. They identified and described any spontaneous intrusive visual memories they had experienced in the past week corresponding to these events. About one quarter reported such memories and, as predicted, the majority of intrusive memories concerned illness, injury and death. The mean levels of intrusion and avoidance were equivalent to patients with post-traumatic stress disorder. Consistent with prediction, depressed patients reported significantly more intrusive memories than controls, and described the memories as typically beginning with or being exacerbated by the onset of depression. Greater numbers of intrusive memories were associated with more maladaptive coping, and greater avoidance with deficits in autobiographical memory functioning.

Introduction Recent research has found that depressed patients, like patients with post-traumatic stress disorder, report high levels of intrusive visual memories of stressful life events. These intrusive memories may involve incidents of childhood abuse (Kuyken and Brewin, 1994a) and of more recent stressors such as the death of loved ones (Brewin et al., 1996c). Moreover, within depressed samples, increased levels of intrusive memories are associated with increased levels of depressive cognition (Kuyken and Brewin, 1995Kuyken and Brewin, in press). However, it is not known whether these repetitive memories are present at an equally high frequency before an individual becomes depressed, or whether the onset of depression is associated with an increase in their frequency. None of the studies so far carried out have included nondepressed controls, so it is also possible that intrusive memories are temporarily triggered by concurrent stimuli such as life stresses and not by depression itself. In this investigation we therefore compared intrusive memories in matched samples of depressed and nondepressed individuals with the common stressor of a cancer diagnosis. We also sought to replicate our previous finding that the avoidance of repetitive intrusive memories is associated with problems in autobiographical memory functioning that are a characteristic feature of depressive thinking (Kuyken and Brewin, 1995). Beck's (Beck et al., 1979) cognitive theory of depression proposed that negative life events activate latent schemes in memory that represent an accumulation of relevant past experience. The activation of schemes containing negative information about the self and the world, Beck suggested, influences the style and content of depressive thinking, leading to more severe and prolonged depression. Research in social cognition has emphasized, however, that representations of the self in memory include specific autobiographical episodes as well as global trait judgements (Smith, 1990; Klein and Loftus, 1993). Studies of anxious and dysphoric individuals have confirmed that self-concept discrepancies are linked to autobiographical episodes. Thus, priming these individuals with trait words relevant to areas in which they feel deficient enhances the accessibility of specific negative memories (Strauman, 1992). Empirical confirmation that depression is associated, not only with the activation of generalized negative beliefs, but also with the intrusion of highly specific autobiographical memories, is consistent with laboratory research and promises to yield important insights into the origins and formation of depressive thinking. Our previous work indicated that the avoidance of intrusive memories of childhood abuse episodes by depressed patients is related to a more global difficulty in retrieving specific autobiographical memories to positive and negative cues (Kuyken and Brewin, 1995). This problem of overgeneral recall is frequently found in depressed and suicidal patients and may influence the course of depression via its impact on problem-solving (Williams and Broadbent, 1986; Williams and Scott, 1988; Williams, 1992). The present study provided an opportunity to test whether intrusive memories related to different kinds of event might predict autobiographical memory functioning in depressed patients. We also found that higher levels of intrusive memories of childhood abuse were related to depressive cognitions such as a more negative attributional style and lower self-esteem, and to a more avoidant coping style (Kuyken and Brewin, in press). This latter association is of interest in light of a recent theory concerning the processing of traumatic memories. Brewin et al. (1996b)suggested that, following a trauma, memories of the experience may eventually cease to intrude either because they have been successfully processed, or because they have been prematurely inhibited. Premature inhibition, brought about perhaps as a result of cognitive avoidance, would leave the memories vulnerable to reactivation at a future time. Brewin et al. further proposed that an episode of depression might be a factor leading to the reactivation of traumatic memories that had been incompletely processed. In depressed patients, levels of intrusion and avoidance of these memories, as measured with standardized instruments such as the Impact of Event Scale (Horowitz et al., 1979) were equivalent to those found in patients with post-traumatic stress disorder (Kuyken and Brewin, 1994a; Brewin et al., 1996c). This permits an inference that the intrusive memories of our depressed samples were at an abnormal level, but without the proper control group this conclusion remains weak. A relatively stringent test of the hypothesis that depression is associated with an increase in the accessibility of specific autobiographical memories would involve comparing depressed and nondepressed samples who had both been exposed to similar types and degree of stress, so that the effects on memory of current environmental circumstances were matched as closely as possible. Two other methodological controls would give greater confidence in these findings. First, patients with comorbid post-traumatic stress disorder, an alternative source of intrusive memories, should be excluded from the depressed sample. Second, it would be necessary to ask the depressed group whether the onset of depression was associated with the start or with an exacerbation of intrusive memories, to guard against the possibility that they had always had high levels of such memories, even before they became depressed. Cancer patients appeared to be a particularly suitable group to study for a number of reasons. First, a cancer diagnosis is well known to be associated with depression (Spiegel, 1996). Also, since cancer is a major cause of mortality, many individuals will have relevant past experiences of the illness or death of close relatives or friends. Finally, cancer treatment is complicated, demanding, and time-consuming, providing many opportunities for cueing recall of autobiographical memories. It would be of considerable interest to know if depressed cancer patients are repeatedly exposed to memories of specific prior experiences involving cancer. Access to information in memory involving pain, illness and death of their loved ones might, for example, contribute to negative expectations concerning their current treatment and quality of life, exacerbating helplessness and hopelessness, and leading to more anxious preoccupation with their illness, and more avoidance coping. Similarly, constantly replaying their own experiences of cancer diagnosis and treatment might in some instances worsen depression. Intrusive memories are not exclusively associated with depression, but may occur in nonclinical samples (Brewin et al., 1996a). Thus we expected a certain number of nondepressed cancer patients to report intrusive memories. However, the major prediction of this study was that depressed patients would report significantly more intrusive memories than controls, even when differences in cancer variables, other unrelated life events and childhood adversity were controlled. Patients were expected to report that onset of depression had been associated with an onset of intrusive memories or with an exacerbation of existing intrusive memories. Following cognitive theory (Beck et al., 1979), it was further expected that the majority of these intrusive memories would be related to relevant past experiences, such as witnessing illness and death. Following previous work (Watson et al., 1994; Kuyken and Brewin, in press), intrusive memories were expected to be associated with poor coping, specifically anxious preoccupation, and helpless and hopelessness. Since depression has been found to be associated with avoidance coping in depressed psychiatric patients (Kuyken and Brewin, 1994b) but not in depressed cancer patients (Watson et al., 1994), no specific predictions were made concerning this variable. It was further predicted that, in line with the findings from studies of autobiographical memory in depressed psychiatric patients, overgeneral memories would be more common among depressed cancer patients, and that overgeneral memories would be associated with more attempts to avoid intrusive memories of upsetting events.

. Results 3.1. Characteristics of the groups Of the depressed sample, only 28 met DSM-IV criteria for a major depressive episode. It was therefore decided to compare the nondepressed controls both with this group (the severely depressed) and with patients scoring more than 8 on the HAD depression scale but not meeting DSM-IV criteria (the mildly depressed). Prior to any analysis six patients who met diagnostic criteria for post-traumatic stress disorder were excluded from the sample (5 severely depressed and 1 control patient). The three groups did not differ significantly in sex (χ2(2)<1), age (F(2,121)<1), time since diagnosis (F(2,120)<1), stage of illness (F(2,121)=1.13, p>0.10), or type of cancer (χ2(8)<1). Nor did the groups differ in number of deaths experienced (F(2,121)=1.86, p>0.10), number of other life events experienced (F(2,121)=1.74, p>0.10), or experience of any childhood adversity (F(2,121)<1). The groups did differ on HAD depression (control x̄=1.81, mildly depressed x̄=9.84, severely depressed x̄=10.70, F(2,121)=357.4, p<0.001). Post hoc tests (least significant difference) indicated that the controls differed from both depressed groups (p<0.05), who did not differ from each other. The groups did not differ on number of previous episodes of depression (F(2,93)=1.62, p>0.10), and the two depressed groups did not differ on the length of the current depressive episode (F(1,34)<1. The groups did differ on age at leaving full-time education (control x̄=15.7, mildly depressed x̄=16.3, severely depressed x̄=17.6, F(2,109)=3.58, p<0.05. Post hoc tests indicated that the severely depressed differed from the controls (p<0.05). However, owing to historical changes in the school leaving age, age at leaving full-time education is confounded with patient age, with a significant negative correlation of r(112)=−0.36, p<0.001. All the variables on which groups were to be compared were therefore checked for possibly confounding associations with age at leaving full-time education (excluding the separate effect of age). No such confounding associations were evident. 3.2. Number and characteristics of intrusive memories Twenty-nine patients (23%) reported an intrusive memory, of whom 12 reported at least one additional memory. In 8 of these 12 cases, the second memory was related to the same incident as the first memory, and in the remaining 4 cases the second memory referred to a completely separate incident. Detailed information was collected on a total of 41 memories. The duration of the memories was as follows: 3/35 lasted seconds, 18/35 lasted minutes, 7/35 lasted up to an hour, 6/35 lasted several hours, and 1/35 was constantly present (6 patients were unable to answer or were not asked the question). 27/41 memories intruded once a week or less, and 14/41 intruded several times a week or more. Overwhelmingly the memories were vivid (38/41) rather than unclear or with some detail only (3/41 for these combined categories). 17/40 memories were accompanied by physical sensations (one patient was not asked the question). Patients experienced themselves as reliving 17/41 memories, and as looking back at the remaining 24/41 memories in the past. The mean level of distress was 6.72 (SD 2.7). The mean IES score of all intrusive memories was 42.03 (range 18–67). 3.3. Content of intrusive memories Twenty-four of the memories (59%) referred to the illness, injury, or death of a relative or friend. Of these 24, 11 (46%) referred to an episode involving death from cancer. This proportion approximated patients' experience of deaths from cancer among their relatives and friends expressed as a proportion of all deaths they had experienced (50%). A further 7 (17%) intrusive memories involved the patient's own experiences of having cancer, such as being given the diagnosis. Thus 76% of the intrusive memories were clearly related to illness, injury and death, and 44% specifically to cancer. 3.4. Intrusive memories and coping with cancer Table 1 shows the correlations between mean scores on the 5 subscales of the Mini-Mac measure and the total number of intrusive memories patients reported. Intrusive memories were significantly positively associated with anxious preoccupation and helplessness/hopelessness, and showed marginally significant associations with cognitive avoidance and fatalism. Table 1 also shows that these associations were still significant or increased in significance after controlling for levels of depression. Table 1. Correlations between intrusive memories and coping with cancer Mini-MAC subscales Number of intrusive memories Number of intrusive memories (controlling for depression) Anxious preoccupation 0.22∗ 0.23∗ Cognitive avoidance 0.19 0.24∗ Fatalism 0.21 0.23∗ Fighting spirit 0.00 0.07 Helplessness and hopelessness 0.34∗∗ 0.24∗ ∗∗ p<0.01; ∗p<0.05 (1-tailed). Table options 3.5. Intrusive memories and depression As predicted, despite the similarities in deaths experienced, other life events, and childhood adversity, the three groups differed markedly in the likelihood of reporting intrusive memories. Seven controls (11%), 12 mildly depressed (32%), and 10 severely depressed (43%) reported at least one intrusive memory. There was a highly significant group difference in the mean number of memories reported (control x̄=0.23, mildly depressed x̄=0.54, severely depressed x̄=0.78, F(2,121)=5.57, p<0.01). Post hoc tests indicated that the controls differed significantly from the other two groups (p<0.05), who did not differ from each other. Participants in the depressed groups were more likely to report that their first intrusive memory had begun with or been exacerbated by the onset of depression (13/20 instances) than that the memory had stayed the same (5/20 instances) or lessened in intensity with the onset of depression (2/20 instances). This distribution differed significantly from chance, χ2(2)=9.71, p<0.01. 3.6. Depression and autobiographical memory The three groups were compared on indices of autobiographical memory functioning, as shown in Table 2. The groups did not differ on latency to retrieve either positive memories (F(2,112)=1.44, p>0.10) or negative memories (F(2,112)=1.52, p>0.10). When the latency data were reanalyzed excluding trials on which no specific memory had been retrieved, these nonsignificant findings remained essentially unchanged. Table 2. Autobiographical memory functioning and depression Latency to specific memory Number of general first memories Group n M SD M SD Positive cue Controls 62 29.5 11.5 1.37 1.23 Mildly depressed 32 34.1 14.3 1.71 1.24 Severely depressed 21 30.9 11.3 1.86 1.42 Negative cue Controls 62 32.2 11.6 1.50 1.25 Mildly depressed 32 36.1 10.3 1.94 1.03 Severely depressed 21 34.9 10.4 2.33 1.20 Table options Table 2 also shows the mean number of general memories retrieved to each kind of cue. There was a significant group difference in the total number of overgeneral memories (F(2,111)=3.85, p<0.05), post hoc tests showing the severely depressed to have more overgeneral memories than the controls (p<0.05). The groups did not differ significantly in their response to positive cues (F(2,111)=1.47, p>0.10), although the means were in the expected direction. There was however a significant group effect for negative cues (F(2,111)=4.28, p<0.02). Post hoc tests once again showed that the severely depressed retrieved significantly more overgeneral memories than the controls (p<0.05). Finally, within the sample of patients with intrusive memories, the number of overgeneral memories produced by each patient was correlated with their IES scores for the first memory. Overgeneral memories were correlated r(24)=0.05, 0.46, and 0.35 with intrusion, avoidance, and total IES score respectively. Avoidance was still significantly associated with number of overgeneral memories after controlling for HAD depression scores, partial r=0.47, p<0.05 (2-tailed).