Various forms of cognitive-behavior therapy (CBT) have demonstrated efficacy in the treatment of obsessive-compulsive disorder (OCD). Response rates for individuals who complete exposure and response prevention (ERP), a first-line treatment for OCD (e.g., [1
]), are as high as approximately 85% (e.g., [2
]). However, because ERP requires patients to engage in prolonged exposure to their feared stimuli while refraining from compulsions, the prospect of ERP is intimidating and the emotional toll of treatment can be difficult to tolerate. Drop-out and refusal rates for ERP are therefore relatively high. Notwithstanding the unambiguous evidence base for this treatment, there is a clear need for alternative therapeutic approaches.
Cognitive therapy (CT) appears to be an efficacious alternative to ERP. According to cognitive models, intrusive thoughts themselves are not pathological; rather, OCD is the result of a pattern of maladaptive beliefs about those thoughts and their meaning (e.g., [3
]). Individuals with OCD tend to perceive intrusive thoughts as dangerous and significant, leading to anxiety and compensatory compulsions. Particular domains of belief that are related to OCD include importance and control of thoughts, inflated responsibility, intolerance of uncertainty, perfectionism, and overestimation of threat [4
]. During CT, patients learn to notice their maladaptive patterns of thinking, reevaluate their beliefs, and ultimately modify them to alleviate distress and reduce obsessions. Patients also conduct behavioral experiments to test predictions based on beliefs in order to correct their assumptions and alter their behavior accordingly. Although these experiments are a form of exposure, they are not designed to induce prolonged discomfort and promote habituation as it typical of ERP.
A number of studies provide evidence supporting the efficacy of CT for OCD (e.g., [5
]). Following these studies, our group developed a CT protocol for OCD to be delivered in a flexible, modular format tailored to the belief domains most relevant to individual patients' idiographic presentations [7
]. In a small open trial, modular CT was associated with moderate decreases in OCD symptoms, especially among patients who had not received previous behavior therapy [8
]. The results of a waitlist controlled trial revealed that individuals who received CT experienced large decreases in OCD symptoms that were largely maintained for at least 12 months [9
A primary impetus to develop multiple efficacious treatments for a given disorder is to accommodate individual differences in treatment response and patient preference. Hence, efforts to identify predictors of treatment outcome can improve patient care by guiding treatment selection. The aim of this study is to identify potential predictors of treatment outcome using data from both the pilot study and waitlist controlled trial of modular CT for OCD [9
]. Based on clinical experience and previous research on predictors of outcome for various OCD treatments, we identified several potential predictor variables as detailed below. Although guided by informed hypotheses, this investigation is exploratory.
Pre-treatment OCD severity predicted worse post-treatment outcome in several studies of various forms of CBT [2
], although not in others (cf. [14
]). However, even if pre-treatment severity predicts post-treatment symptom severity, participants may improve at the same rate over time regardless of initial severity. Hence, one aim was to evaluate the impact of pre-treatment severity on the rate of improvement from CT over the course of treatment.
The relationship between Axis I comorbidity and treatment outcome is equivocal. The results of several investigations of depression or depressive symptoms are mixed and few studies have examined any other comorbid disorders (for a review see [17
]). Several studies, however, have found that although the presence of comorbidity was associated with increased pre-treatment severity in various internalizing disorders, it did not adversely affect treatment outcome [18
]. In light of these studies, another aim was to evaluate the impact of Axis I comorbidity on treatment outcome in CT for OCD.
Clinical experience and empirical data suggest that symptoms of personality disorders can interfere with treatment. Most clear is the relationship between traits of schizotypal personality disorder and negative outcome in OCD treatments (e.g., [21
]), although other studies implicate other personality clusters, as well (e.g., [10
]). We therefore examined the relationship between personality disorder traits and outcome.
A number of studies have found that sexual and religious obsessions are associated with poor outcome in CBT and pharmacotherapy ([12
]; but see [29
]). Among many possible reasons, sexual and religious obsessions may be difficult to treat because they are associated with greater reluctance on the part of patients to risk moral consequences, difficulty designing in vivo exposures that confront such consequences, poor insight, and especially distorted thinking (e.g., [17
]). Some have suggested that CT is particularly well-suited for sexual and religious obsessions (e.g., [7
]). In contrast, the presence of contamination and washing symptoms may predict worse response to CT [7
]. We therefore investigated the relationships between treatment outcome and sexual, religious, and contamination obsessions.
Patient motivation and expectancy have also been implicated as potential moderators of outcome. Clinical experience suggests that patient motivation is a critical prerequisite for treatment success, particularly in intensive ERP (e.g., [32
]). Indeed, several studies have found that motivation predicted positive treatment outcome in both CBT and pharmacotherapy for OCD (e.g., [10
]; but see [34
]), and at least two studies are in progress to investigate the utility of adding motivational enhancement techniques to improve outcome [35
]. In addition, some have argued that a sizable portion of variance in treatment effects can be attributed to patient expectations (e.g., [37
]). However, expectancy did not predict treatment outcome in four studies of CBT for OCD [34
]. In light of these studies, we also examined patient motivation and expectancy as possible predictors.
Finally, in light of the notable relationship between OCD and disability (e.g., [41
]) and previous studies showing poor functioning to be a predictor of negative outcome (e.g., [42
]), we investigated whether pre-treatment disability was related to CT outcome.
Analyses of three domains were conducted to identify factors that may impact the effectiveness of CT on OCD: 1) predictors of early drop-out; 2) predictors of change in OCD symptom severity during treatment; and 3) predictors of change in OCD symptom severity at follow-up.