D-cycloserine as adjunct to brief computerised CBT for spider fear: Effects on fear, behaviour, and cognitive biases

In anxiety disorders, cognitive behavioural therapy (CBT) improves information-processing biases such as implicit fear evaluations and avoidance tendencies, which predicts treatment response. Thus, these cognitive biases might constitute important treatment targets. This study investigated (i) whether information-processing biases could be changed following single-session computerised CBT for spider fear, and (ii) whether this effect could be augmented by administration of D-cycloserine (DCS).

Spider-fearful individuals were randomized to receiving either 250 mg of DCS (n = 21) or placebo (n = 17). Three hours after drug administration, they received single-session computerized CBT, characterized by psychoeducation and exposure elements. Spider fear was assessed using self-report, behavioural, and information processing (Extrinsic Affective Simon Task & Approach Avoidance Task) measures at baseline (before drug administration), post-treatment, 1-day, and 1-month follow-up.

Linear mixed-effects analyses indicated significant improvements on self-report and behavioural spider fear indices following CBT, but not on cognitive bias measures. There was no evidence of an augmentation effect of DCS on any outcome. Cognitive bias measures at 1-day were not predictive of 1-month follow-up spider fear in adjusted linear regression analyses.

Results might be biased by limited representativeness of the sample (high education and intelligence, largely Caucasian ethnicity, young age). The study was also only powered for detection of medium-sized DCS effects.

These findings do not provide evidence for information-processing biases relating to treatment outcome following computerised CBT for spider fear or augmentation with DCS.