All at once or one at a time? A randomized controlled trial comparing two ways to deliver bibliotherapy for panic disorder.

Bibliotherapy is potentially effective in the treatment of panic disorder (PD). A still unanswered question is whether pacing is important. This study was designed to test whether there is a difference between being assigned a full book as therapy and receiving one individual chapter every week (i.e. pacing). A total of 28 participants were randomized to either 10 paced chapters or one book with 10 chapters. To maximize compliance, short weekly telephone calls were added in both conditions (M = 17.8 min, SD = 4.2). Both treatments showed promising results, with effects maintained up to 2 years and with within-group effect sizes (Cohen's d) between 0.95 and 1.11. Pretreatment ratings of credibility were positively correlated with the change scores at both posttest and 2-year follow-up for three panic measures. Pacing of text material in bibliotherapy for PD is not needed, and all material can be provided at once when the treatment is guided by a therapist.