Original Paper Psychopathology 2007;40:147–152 DOI: 10.1159/000100003
Received: May 2, 2005 Accepted after revision: February 2, 2006 Published online: February 22, 2007
Changes in Autobiographical Memory Specificity following Cognitive Behavior Therapy and Pharmacotherapy for Major Depression Carolina McBride a Zindel Segal a Sidney Kennedy b Michael Gemar a a
Centre for Addiction and Mental Health, and b University Health Network, University of Toronto, Toronto, Ont., Canada
Key Words Autobiographical memory Overgeneral memory Cognitive behavioral therapy Pharmacotherapy
Abstract Background: An important cognitive marker of clinical depression is a reduced ability to be specific in recalling personal memories, a phenomenon coined ‘overgeneral memory’. Overgeneral memory is considered as a stable cognitive trait that is intrinsically linked with depression and independent of mood state. Previous studies show that autobiographical memory is modifiable. Sampling and Methods: This study investigated whether autobiographical memory is differentially affected by treatment type. Depressed patients were randomly assigned to receive either cognitive behavior therapy (CBT) for depression or pharmacotherapy (PHT). Results: The proportion of categoric memories decreased and the proportion of specific memories increased following both types of treatments, adding support to the view that overgeneral memory is modifiable. CBT also had a greater impact on reducing extended overgeneral memories compared to PHT. Conclusions: The results from the current study are important in that they show that overgeneral memory can be targeted and modified through brief treatment. The clinical significance of the finding that there was a greater decrease in extended memories in the CBT group is unclear. Copyright © 2007 S. Karger AG, Basel
© 2007 S. Karger AG, Basel 0254–4962/07/0403–0147$23.50/0 Fax +41 61 306 12 34 E-Mail
[email protected] www.karger.com
Accessible online at: www.karger.com/psp
Introduction
Depressed individuals tend to generate more general memories of their past than nondepressed individuals. For example, in response to a word cue such as ‘sad’, a depressed person may respond, ‘every Christmas’ whereas an individual who is not depressed may respond, ‘The day I discovered that my mother was diagnosed with cancer’. This phenomenon has been described as ‘overgeneral memory’ [1, 2]. More recently, within overgeneral autobiographical memory, Williams [2] has introduced an important distinction between two types of retrieval errors that can lead to overgeneral memory: categoric errors, which refer to summaries of memories (e.g., ‘every time I go to the gym’), and extended errors, which refer to memories where the event remembered lasts longer than the time interval of one day (e.g., ‘during the winter months’). Categoric and extended errors in memory are regarded as functionally independent of each other [3], and research suggests that overgenerality in depressed individuals is wholly attributable to an excess of categoric errors [2]. Overgeneral memory has been conceptualized as a cognitive trait that reflects vulnerability towards clinical depression [2]. In other words, overgeneral memory is considered as an enduring feature that is intrinsically linked with clinical depression, the current state of mood being of little influence [2]. Several attempts have been made to answer the question of stability in overgeneral recall.
Dr. Carolina McBride Interpersonal Psychotherapy Clinic, Centre for Addiction and Mental Health Clarke Site, 250 College Street, Toronto, Ontario, M5T 1R8 (Canada) Tel. +1 416 535 8501/ext. 6130, Fax +1 416 979 6815 E-Mail
[email protected]
In support of the view that overgeneral memory is independent of mood state, Williams and Dritschel [3] found that previously suicidal patients who had recovered from clinical depression remained significantly more overgeneral in their memories compared to nondepressed controls. However, the argument for stability of autobiographical memory was mitigated by the fact that the mood state of recovered patients was not different from a third group of individuals who had very recently taken an overdose. In another attempt at answering the question of stability, Brittlebank et al. [4] found that depressed individuals continued to show overgenerality in recalling personal memories during the course of recovery from depression. However, analysis of change in autobiographical memory test (AMT) scores was limited to a small number of patients. More recently, Peeters et al. [5] found that autobiographical memory was stable over time despite clinical improvement in mood in a sample of depressed patients. Nadrino et al. [6] found that overgeneral memory remains stable during treatment in patients with more than three prior episodes of depression but not in patients with lower numbers of prior episodes. A final study comparing two groups of nondepressed individuals – one with a lifetime prevalence of major depression and one without – found that women without a lifetime prevalence of depression retrieved significantly more specific memories and significantly less categoric memories than women in remission from major depression, [7]. This difference was only found for negative cues. There is also evidence to suggest that overgeneral autobiographical memory is modifiable. Kuyken and Dalgleish [8] compared previously depressed to never-depressed individuals and found no difference between groups in their tendency to retrieve general memories, suggesting a return to autobiographical memory specificity upon recovery from an episode of depression. More recently, Watkin et al. [9] showed that cognitive manipulation influences the recall of categorical memories in dysphoric patients. More specifically, a distraction manipulation produced significantly greater decreases in the proportion of memories retrieved that were categorical than a rumination manipulation. In another study investigating the modifiability of overgeneral memory, Williams et al. [10] showed that overgenerality in memory could be reduced by treatment. Depressed patients in remission were randomly allocated to receive either treatment-asusual or a program of treatment designed to reduce risk of relapse (mindfulness-based cognitive therapy, MBCT). Results demonstrated that patients in the MBCT group had an increased specificity of memory and a significant 148
Psychopathology 2007;40:147–152
reduction in the number of categoric memories compared to patients in the treatment-as-usual group. Finding that overgeneral memory is modifiable, however, does not necessarily refute the view that this phenomenon is a stable cognitive trait. Indeed, cognitive vulnerability markers of depression may be stable traits, yet the expression of these dysfunctional processes may be dependent on the state of mood [11, 12]. A consensus is emerging among researchers that some cognitive vulnerability factors can be modified [11–16]. In line with this, Williams et al. [10] argued that the memory changes they observed in the MBCT group were not mood driven and therefore were not state dependent. The results of Williams et al. [10] are exciting in that specificity of autobiographical memory was differentially modified according to type of treatment offered, with cognitive interventions having a greater influence on changes in autobiographical memory specificity than non-cognitive interventions. These results are promising because they suggest that different interventions can have a differential influence on autobiographical memory recall. If autobiographical memory is indeed a cognitive marker of depression as accumulating evidence seems to suggest [7, 17–20], finding a differential change in autobiographical memory specificity according to treatment type is important as it shows that this cognitive vulnerability can be targeted through specific intervention. Successful treatment of depression not only requires a successful resolution of depressed symptoms but, more importantly, change in the underlying, stable vulnerability aspects that increase susceptibility for repeated episodes [13, 21, 22]. The purpose of the research reported here is to investigate the effect of two empirically validated and distinct treatments for depression on autobiographical memory recall. Depressed patients were randomly assigned to either cognitive behavior therapy (CBT) or pharmacotherapy (PHT), and autobiographical memory was tested before and after treatment. While both CBT and PHT treatment produce equivalent treatment outcomes, the mechanisms of change likely differ. In CBT, symptom reduction is thought to occur through change in cognition [16], whereas the interventions in PHT are neurobiological and depend only minimally on cognitive restructuring. The expectation, therefore, was that autobiographical memory would become less overgeneral following CBT treatment compared to PHT treatment. More specifically, a greater reduction in categoric memories and a greater increase in specific memories were expected following CBT treatment compared to PHT treatment. McBride /Segal /Kennedy /Gemar
Participants and Methods Participants The sample was derived from a larger database of outpatients who participated in a randomized clinical treatment trial, and consisted of 42 patients (13 men, 29 women) diagnosed with unipolar, non-psychotic major depression. The sample was derived from all the participants in the larger database who completed the AMT before and after treatment. Stratified random sampling was employed with participants matched for gender and number of previous episodes of depression. Twenty-one patients were randomly assigned to the CBT group and 21 to the PHT group. The mean age of the sample was 40.71 years (SD = 10.79). Most of the sample (95.2%) had completed high school. In terms of number of previous episodes of depression, 61.9% of the sample had 63 past episodes, and 38.1% had ^2 past episodes. There were no differences between the groups in terms of age, education, or number of previous episodes of depression. The local research ethics board stipulated that research participants were not obligated to disclose racial and ethnic information; however, the general impression was that the sample was predominantly Caucasian. These patients were recruited through newspaper advertisements for a study on depression and relapse. To be included in the treatment trial the patients had to (1) meet the DSM-IV criteria [23] for non-psychotic, major depression based on the Structured Interview for DSM-IV, Axis-I Disorders (SCID-I/P) [24], (2) be between the ages of 18 and 60, (3) be medication-free (i.e., of antidepressants) for a minimum of 2 weeks prior to treatment, (4) have minimum eight grade education and fluency in reading English and (5) have the ability to give informed consent and complete assessment instruments unassisted. Patients were excluded if they met DSM-IV criteria for bipolar disorder (past or present), psychotic disorders, substance abuse or dependence disorders (current or within the past 6 months), borderline or antisocial personality disorder, or organic brain syndrome. Patients were also excluded if they had received electroconvulsive therapy within the past 6 months or had a concurrent active medical illness. Measures Beck Depression Inventory-II (BDI-II). The BDI-II [25] is a widely used 21-item self-report measure of severity of depression. The BDI-II is scored by summing the ratings for the 21 items, with the maximum score being 63. Higher scores indicate higher levels of depressive symptoms. The BDI-II has good internal consistency, retest reliability, and concurrent and construct validity [25]. AMT. The emotional cue words were those used by Williams and Broadbent [1]. There were five positive words (happy, safe, interested, successful and surprised), and five negative words (sorry, angry, clumsy, hurt and lonely). Instead of the words being read to the participants as in the Williams and Broadbent [1] paradigm, they were presented on a two-sided sheet of paper, alternating between positive and negative cue word, with two cue words per page. Participants were required to provide a written report of their memory for each cue word; they were not given a time limit to complete the task. Memories were categorized according to the following criteria: (1) specific memories: a memory was deemed specific if the participant recalled an event referring to one particular day. (2) Extended general memories. A memory was classified as extended if
Changes in Autobiographical Memory Specificity
Table 1. Means and standard deviations for BDI-II Scores at time 1 and time 2 for CBT and PHT groups
Time 1 Time 2
CBT group (n = 21)
PHT group (n = 21)
30.6788.78 12.62810.82
31.67810.15 10.0088.63
it referred to an event that lasted more than 1 day. (3) Categoric general memories: a memory was classified as categoric if it referred to a series of repeated events. (4) Nonautobiographical: a memory was classified as nonautobiographical if it did not correspond to an actual memory and appeared to be a word association. (5) Omission: an omission was coded if the participant left the response area blank. Nonautobiographical memories and omissions were excluded from the analyses. Each memory was rated independently by two raters who were blind to the treatment condition. The raters were trained by the principal author using responses to the AMT from an unpublished study. Inter-rater agreement for the 10 pre- and post-treatment cue words ranged between 80 and 100%. Disagreements between ratings were resolved with the principal author. Procedure Those who responded to the advertisement underwent a telephone screen and, if eligible, were invited to an assessment interview. Those who were eligible for the study were invited to participate and asked to complete assessment measures. Patients were then randomly assigned to 16 weekly sessions of CBT or 16 weeks of PHT treatment for depression. Autobiographical memory was tested on two occasions, once before randomization to CBT or PHT (time 1), and again after the termination of treatment (time 2). Four months elapsed between time 1 and time 2 and, therefore, the authors were confident that a repetition effect for the cue words would not occur.
Results
Alpha was set at 0.05 for all analyses. Mood Means and standard deviations for time 1 and time 2 BDI-II scores are shown in table 1. One-way ANOVAs revealed that there were no differences between the groups on BDI-II scores at time 1 or at time 2. In order to examine if there was a differential change in mood by treatment, a 2 (time: 1, 2) ! 2 (group: CBT, PHT) mixed ANOVA was carried out for BDI-II scores. We found a significant main effect for time for the BDI-II scores: F (1, 40) = 116.31, MSE = 71.20, p ! 0.001. The main effect for group and the time-group interaction were not signifiPsychopathology 2007;40:147–152
149
Table 2. Proportion of specific, categoric,
and extended memories at times 1 and 2 for CBT and PHT groups
CBT group (n = 21)
PHT group (n = 21)
Memories
time 1
time 2
time 1
time 2
Specific positive Specific negative Extended positive Extended negative Categoric positive Categoric negative
0.6580.20 0.5280.32 0.1980.17 0.1080.12 0.1680.16 0.3880.33
0.7480.29 0.6780.33 0.1280.15 0.0480.10 0.1480.21 0.2980.32
0.6780.22 0.4980.33 0.1080.13 0.1280.17 0.2380.25 0.3980.38
0.7380.25 0.5280.28 0.1380.17 0.1680.19 0.1480.26 0.3280.28
cant, indicating that both treatments were equally effective in decreasing symptoms of depression. AMT To test the hypothesis that autobiographical memory would become less overgeneral following CBT treatment compared to PHT treatment, we analyzed the data for the proportion of memory responses that were of each memory type (specific, categoric, extended) with a separate 2 (group: CBT, PHT) ! 2 (time: 1, 2) ! 2 (valence: positive, negative) mixed analysis of covariance, covarying out BDI-II scores at time 2. Means and standard deviations are shown in table 2. A 2 ! 2 ! 3 analysis of covariance showed no significant main effects or interactions for omissions and non-autobiographical memories and, therefore, these types of memories will not be discussed further. Proportion of Specific Memories. There was a main effect of time: F (1, 39) = 4.38, MSE = 0.28, p ! 0.05, and valence: F (1, 39) = 5.39, MSE = 0.31, p ! 0.05. The proportion of specific memories increased at post treatment, and there was a greater proportion of positive specific memories recalled compared to negative specific memories. There was no significant main effect for group and no significant interactions. Proportion of Categoric Memories. There was a main effect of time: F (1, 39) = 5.66, MSE = 0.33, p ! 0.05, and a main effect of valence: F (1, 39) = 14.71, MSE = 0.56, p ! 0.01. The proportion of categoric memories decreased at post treatment, and there was a greater proportion of negative categoric memories recalled compared to positive categoric memories. There was no significant main effect for group and no significant interactions. Proportion of Extended Memories. The time-group interaction was significant: F (1, 39) = 4.71, MSE = 0.10, p ! 0.05. This interaction was due to a greater decrease in extended memories in the CBT group compared to in the PHT group. There was also a significant valence-treat150
Psychopathology 2007;40:147–152
ment condition interaction: F (1, 39) = 4.58, MSE = 0.14, p ! 0.05, with the PHT group producing more negative extended memories compared to the CBT group at time 2. The main effect of group, time, and valence were not significant.
Discussion
The aim of the present study was to examine if two well-known and empirically validated treatments for depression, CBT and PHT, would have an impact on autobiographical memory recall. The results suggest that overgeneral memory is in fact modifiable and can be reduced by treatment. The changes in memory observed occurred after controlling for depression scores after treatment, which is consistent with earlier studies [7, 10, 17] showing that memory changes are not mood driven. The hypothesis that CBT would have a greater influence on the recall of overgeneral memories than PHT was not supported by the results. Both treatments were equally effective in decreasing the proportion of overgeneral memories retrieved. The results from the current study are consistent with previous research[10] suggesting that treatment has a specific effect on categoric and specific autobiographical memories. In both the CBT and the PHT groups, the proportion of categoric memories decreased and the proportion of specific memories increased after treatment. Changes were not observed for memories classified as extended. Although there was no significant main effect of time for extended memories, the group-time interaction was significant due to a greater decrease in extended memories in the CBT group compared to the PHT group. Furthermore, the results showed that the CBT group produced a lesser proportion of negative extended memories than the PHT group at time 2. These results are interestMcBride /Segal /Kennedy /Gemar
ing in that they suggest that an intervention that specifically targets the cognitive system exerts a greater change in one type of overgeneral memory than an intervention that does not specifically target the cognitive system. However, research indicates that categoric memory is the pathological form of overgeneral memory, not extended memory and, therefore, it is unclear whether these results are of clinical significance. On the other hand, the occurrence rates for extended memories are generally very low and this may contribute to the finding that they do not distinguish clinical from non-clinical groups. Extended memories might be an indicator not necessarily of psychopathology, but of the efficient use of cognitive resources that can be modified during the treatment process. Replication of our findings and future research would be helpful to determine the clinical significance of extended memories. The current study elicited some interesting results with respect to valence. In particular, there were a greater proportion of positive specific memories recalled in both treatment groups compared to negative specific memories. These results are not consistent with those reported in previous research [3, 26, 27], where increased specificity has been found for negative cues. Why there are differences between our results and those of previous research is not clear, although there are inconsistent results with respect to valence in the literature, with some studies finding a valence effect [e.g., 1, 3, 7, 27] while others did not [e.g., 4, 10]. One limitation of the study is that the same cue words were used both before and after treatment, increasing the
possibility of a repetition memory effect. However, there was a 4-month time period between pre- and post-treatment testing periods, which minimizes the chances that practice and familiarity influenced autobiographical memory recall at time 2. The fact that there was a difference in the direction of the changes observed between specific, categoric and extended memories also minimizes the chances that a repetition memory effect was at play. Another limitation of the study is that participants were required to provide a written report of their memory for each cue word instead of an oral report, as in the Williams and Broadbent [1] paradigm. It is possible that, under these circumstances, the task was slightly less sensitive to detecting subtle differences that might occur between the treatments. Williams [2] has argued that overgeneral memory and, more specifically, categoric overgeneral memory represents a stable cognitive marker that increases an individual’s vulnerability to depression, and there is accumulating evidence to support his claim. The results from the current study are clinically important in that they show that categoric memory can be modified through two brief treatments for depression. This suggests that, in the short term, both treatments are equally effective at targeting and changing a relatively stable cognitive vulnerability factor of depression, which could translate into a reduced probability of recurrence of the disorder. The question remains how long-lasting these changes in memory are, how they relate to relapse, and whether the changes are differentially maintained across CBT and PHT.
References 1 Williams JMG, Broadbent K: Autobiographical memory in suicide attempters. J Abnorm Psychol 1986;95:144–149. 2 Williams JMG: Depression and the specificity of autobiographical memory; in Rubin DC (ed): Remembering Our Past: Studies in Autobiographical Memory. Cambridge, Cambridge University Press, 1996, pp 244–267. 3 Williams JMG, Dritschel BH: Emotional disturbance and the specificity of autobiographical memory. Cogn Emotion 1988; 2:221–234. 4 Brittlebank AD, Scott J, Williams JM, Ferrier IN: Autobiographical memory in depression: state or trait marker? Br J Psychiatry 1993;162: 118–121.
Changes in Autobiographical Memory Specificity
5 Peeters F, Wessel I, Merckelbach H, BoonVermeeren M: Autobiographical memory specificity and the course of major depressive disorder. Compr Psychiatry 2002; 43: 344– 350. 6 Nadino JL, Pezard L, Posté A, Réveillère C, Beaune D: Autobiographical memory in major depression: a comparison between firstepisode and recurrent patients. Psychopathology 2002;35:335–340. 7 Mackinger HF, Pachinger MM, Leibetseder MM, Fartacek RR: Autobiographical memories in women remitted from major depression. J Abnorm Psychol 2000;109:331–334. 8 Kuyken W, Dalgleish T: Autobiographical memory and depression. Br J Clin Psychol 1995;34:89–92.
9 Watkins E, Teasdale JD, Williams RM: Decentering and distraction reduce overgeneral autobiographical memory in depression. Psychol Med 2000;30:911–920. 10 Williams JMG, Teasdale JD, Segal ZV, Soulsby J: Mindfulness-based cognitive therapy reduces overgeneral autobiographical memory in formerly depressed individuals. J Abnorm Psychol 2000;109:150–155. 11 Miranda J, Persons JB: Dysfunctional attitudes are mood-state dependent. J Abnorm Psychol 1988;97:76–79. 12 Miranda J, Gross JJ, Persons JB, Hahn J: Mood matters: negative mood induction activates dysfunctional attitudes in women vulnerable to depression. Cogn Ther Res 1998; 22: 363– 376.
Psychopathology 2007;40:147–152
151
13 Ingram RE, Miranda J, Segal ZV: Cognitive Vulnerability to Depression. New York, Guilford Press, 1998. 14 Gemar MC, Segal ZV, Sagrati S, Kennedy SJ: Mood-induced changes on the Implicit Association Test in recovered depressed patients. J Abnorm Psychol 2001;110:282–289. 15 Segal ZV, Gemar M, Williams S: Differential cognitive response to a mood challenge following successful cognitive therapy of pharmacoptherapy for unipolar depression. J Abnorm Psychol 1999;108:3–10. 16 Beck AT: Cognitive models of depression; in Leahy RL, Dowd TE (eds): Clinical Advances in Cognitive Psychotherapy: Theory and Application. Progr Cogn Dev Res. New York, Springer, 2002, vol 14, pp 29–61. 17 Dalgleish T, Spinks H, Yiend J, Kuyken W: Autobiographical memory style in seasonal affective disorder and its relationship to future symptom remission. J Abnorm Psychol 2001; 110:335–340.
152
18 Kuyken W, Brewin CR: Autobiographical memory functioning in depression and reports of early abuse. J Abnorm Psychol 1995; 4:585–591. 19 McNally RJ, Lasko NB, Macklin ML, Pitman RK: Autobiographical memory in combat-related post-traumatic stress disorder. Behav Res Ther 1995;33:619–630. 20 McNally RJ, Litz BT, Prassas A, Shin LM, Weathers FW: Emotional priming and autobiographical memory in posttraumatic stress disorder. Cogn Emotion 1994;8:351–368. 21 Fava GA, Rafanelli C, Grandi S, Conti S, Belluardo P: Prevention of recurrent depression with cognitive behavioral therapy: preliminary findings. Arch Gen Psychiatry 1998; 55: 816–820.
Psychopathology 2007;40:147–152
22 Hollon SD, Shelton RC, Davis DD: Cognitive therapy for depression: conceptual issues and clinical efficacy. J Consult Clin Psychol 1993; 61:270–275. 23 American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders, ed 4. Washington, American Psychiatric Press, 1994. 24 First MB, Spitzer RL, Gibbon M, Williams JBW: Structured Clinical Interview for DSMIV Axis-I Disorders, Clinician Version (SCIDCV). Washington, American Psychiatric Press, 1996. 25 Beck AT, Steer RA, Brown GK: Manual for Beck Depression Inventory-II, ed 2. San Antonio, Psychological Corporation, 1996. 26 Puffet A, Jehin-Marchot D, Timsit-Berthier M, Timsit M: Autobiographical memory and major depressive states. Eur Psychiatry 1991; 6:141–145. 27 Williams JMG, Scott J: Autobiographical memory in depression. Psychol Med 1988;18: 689–695.
McBride /Segal /Kennedy /Gemar
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
