The Differential Impact of Expectancies and Symptom Severity on Cognitive Behavior Therapy Outcome in Panic Disorder with Agoraphobia

Cognitive behavior therapy (CBT) is the treatment of choice for panic disorder with agoraphobia (PDA). Numerous studies have been conducted on the shortand long-term effectiveness of CBT. Treatment effectiveness could range as low as 25% and as high as 90% (e.g., Barlow et al. 1989; Black et al., 1993; Fava et al., 1995; Margraf et al., 1993; Öst & Westling, 1995; Shear et al., 1994; Taylor et al., 1996). Nevertheless, most studies have concluded that CBT appears to be the most effective treatment to date in reducing panicrelated symptomatology in the shortand long-term (Clark et al., 1994; Craske et al., 1991; Fava, et al., 1995). However, some clients continue to experience anticipatory anxiety and avoidance following CBT (Clark et al., 1994; Craske et al., 1991; Klosko et al., 1990). Brown and Barlow (1995) conducted a long-term outcome study using stringent criteria for treatment efficacy. Although the treatment had produced substantial improvements, their findings revealed that only 20.6% of their sample could be considered as treatment success after two years. One of their recommendations for future studies was to examine predictors of treatment response. Following up on these recommendations, the present study aims to determine why some clients do not respond to CBT or only show partial benefits. Outcome studies have examined the impact of different client variables such as motivation, personality traits, socio-demographic characteristics, diagnosis, and intelligence to name a few. The important role of client variables in psychotherapy has been confirmed in numerous studies since the 1940's (see Garfield, 1986 and Lambert & Assay, 1984). Highlen and Hill (1984) conducted an extensive review on the effects of psychotherapy and concluded that client characteristics are the most important and influential factors relating to treatment outcome and to long-term improvement (Highlen & Hill, 1984). Several variables listed by Highlen and Hill (1984), have been important in predicting treatment outcome and long-term improvement in PDA. For instance, the severity of