*2.4.3. Sleep measures*

*The Nightmare Distress Questionnaire* [*NDQ*; [24]] is a 13-item self-report questionnaire retrospectively evaluating the waking degree of distress associated with experiencing nightmares. It is a 5-point Likert scale from 0 (= *never*) to 5 (= *always*). It demonstrates good psychometric properties. Since the last two items in the questionnaire evaluate the respondent's interest in following a course of therapy, and participants were already enrolled in therapy, we did not consider these two items in the total score. *The Pittsburg Sleep Quality Index Questionnaire* [*PSQI*; [25]] includes 19 self-rated questions and 5 questions rated by the bed partner or roommate if one is available. The total score varies from 0 to 21. It also demonstrates good psychometric properties in English [26]. *The Pittsburgh Sleep Quality Index Addendum for PTSD* [*IQSP-A*; [27]] is a self-report questionnaire designed to assess the frequency of seven PTSD-specific sleep disturbances during the month preceding completion of the questionnaire. A global score is obtained from the sum of all seven items, and has a range of 0 to 21. It demonstrates good psychometric properties [27].
