How Does Cognitive Therapy Prevent Relapse in Residual Depression? Evidence From a Controlled Trial John D. Teasdale Cognition and Brain Sciences Unit Medical Research Council Jan Scott Department of Psychiatry University of Glasgow Richard G. Moore Department of Psychiatry University of Cambridge Hazel Hayhurst Department of Psychiatry University of Cambridge Marie Pope Department of Psychiatry University of Newcastle Eugene S. Paykel Department of Psychiatry University of Cambridge ABSTRACT This study examined the cognitive mediation of relapse prevention by cognitive therapy (CT) in a trial of 158 patients with residual depression. Scores based on agreement with item content of 5 questionnaires of depression-related cognition provided no evidence for cognitive mediation. A measure of the form of response to those questionnaires, the number of times patients used extreme response categories ("totally agree" and "totally disagree"), showed significant and substantial prediction of relapse, differential response to CT, and conformity to mediational criteria. CT reduced relapse through reductions in absolutist, dichotomous thinking style. CT may prevent relapse by training patients to change the way that they process depression-related material rather than by changing belief in depressive thought content. There is encouraging evidence that cognitive therapy (CT; Beck, Rush, Shaw, & Emery, 1979 ) reduces relapse and recurrence in depression. Outpatients who recover following treatment of major depression by CT show less subsequent relapse or need for treatment than patients who recover with pharmacotherapy and are then withdrawn from antidepressant medication ( Blackburn, Eunson, & Bishop, 1986 ; Evans et al., 1992 ; Shea et al., 1992 ; Simons, Murphy, Levine, & Wetzel, 1986 ). CT following recovery with pharmacotherapy can also reduce subsequent relapse and recurrence ( Fava, Grandi, Zielezny, Rafanelli, & Canestrari, 1996 ; Fava, Rafanelli, Grandi, Conti, & Belluardo, 1998 ). In patients responding only partially to antidepressant medication, the addition of CT to clinical management and continuing antidepressant medication significantly reduced rates of relapse ( Paykel et al., 1999 ). The processes through which CT reduces depressive relapse are not well understood. Although a number of proposals have been made (see below), their empirical support is limited. To our knowledge, there is no convincing published evidence that any proposed cognitive mediator satisfies the criteria proposed by Hollon and colleagues ( DeRubeis et al., 1990 ; Hollon, Evans, & DeRubeis, 1990 ). These criteria, adapted from more general mediational criteria ( Baron & Kenny, 1986 ), require that (a) rates Journal of Consulting and Clinical Psychology © 2001 by the American Psychological Association June 2001 Vol. 69, No. 3, 347-357 For personal use only--not for distribution. Page 1 of 199/5/2001http://spider.apa.org/ftdocs/ccp/2001/june/ccp693347.htmlof relapse following CT are significantly less than those in a comparison condition; (b) there is a significant treatment effect on the proposed cognitive mediator; (c) posttreatment measures of the cognitive variable predict subsequent relapse (independent of the prediction from posttreatment depression); (d) prediction of relapse by posttreatment measures of the cognitive mediator remains significant when the variable "treatment" is simultaneously entered into the regression; and (e) inclusion of posttreatment measures of the cognitive mediator reduces the extent to which the variable treatment predicts subsequent relapse. The cognitive model underlying CT for depression suggested that vulnerability was related to underlying dysfunctional attitudes or assumptions (e.g., Beck, Epstein, & Harrison, 1983 ). From this perspective, reduction in relapse following CT is a consequence of CT reducing those dysfunctional attitudes. This hypothesis has received little empirical support ( Barber & DeRubeis, 1989 ); when CT has produced significantly better long-term outcomes than pharmacotherapy, the two treatments often do not differ on posttreatment measures of dysfunctional attitudes such as the Dysfunctional Attitude Scale (DAS; Weissman & Beck, 1978 ; see, e.g., Simons, Garfield, & Murphy, 1984 ). The National Institute of Mental Health Treatment of Depression Collaborative Research Program found no evidence for specific effects of CT on DAS total or perfectionism subscale scores, but there were specific effects on need for social approval subscale scores ( Imber et al., 1990 ). Segal, Gemar, and Williams (1999) reported that, when the DAS was administered following a dysphoric mood induction, posttreatment DAS scores were significantly less following CT than pharmacotherapy. Such scores also predicted subsequent relapse. However, these findings were based on small numbers of patients not randomized to treatment condition. The reformulated learned helplessness model of depression ( Abramson, Seligman, & Teasdale, 1978 ) suggested that vulnerability to depression involves a depressotypic attributional style: a tendency to attribute bad events to internal, stable, and global causes and good events to external, unstable, and specific causes. The Attributional Style Questionnaire (ASQ; Peterson et al., 1982 ) provides a measure of depressotypic attributional style. Hollon et al. (1990) reported that, in Evans et al.'s (1992) clinical trial comparing CT and pharmacotherapy for depression, ASQ satisfied four of the five mediational criteria described above, and they concluded that attributional style "emerges as a potential mediator of cognitive therapy's prophylactic effect on posttreatment relapse/recurrence" ( Hollon et al., 1990 , p. 126). However, more recent analyses have suggested that "strictly speaking [the ASQ] does not meet statistical criteria for mediation" (S. D. Hollon, personal communication, July 5, 1999). DAS- and ASQ-related accounts suggest that CT acts through changes in "deep" schematic cognitive structures or characteristic interpretative cognitive styles. By contrast (see also Persons, 1993 ), Barber and DeRubeis (1989) suggested that the key therapeutic process was not so much cognitive change as the acquisition of compensatory skills: "cognitive therapy does not reduce the tendency for depressives to generate negative thoughts in distressing situations, but rather it inculcates a set of skills that helps them deal with these
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