Emotion Regulation-based Internet-delivered Cognitive Behavioural Therapy for Premenstrual Dysphoric Disorder

The study is a parallel two-group RCT with 1:1 allocation to 8 weeks of a therapist-guided self-help ICBT for PMDD or a waitlist control group. Approximately 164 women (age 18-45) fulfilling the DSM-5 diagnostic criteria for PMDD will be randomly assigned.

Recruitment

Participants will be recruited from the general population using the following screening procedure.

1. Web-based screening for PMDD (Premenstrual Screening Tool) and other eligibility criteria 2. Clinical diagnostic (telephone) interview assessing preliminary PMDD diagnosis and psychiatric comorbidity 3. Prospective daily ratings of premenstrual symptoms during two consecutive menstrual cycles using the Daily Report of Severity of Problems (DRSP).

Outcomes and Expected Results

Primary outcomes are pre- to post-treatment group differences in premenstrual symptoms and their impact on everyday life (prospective daily ratings, two menstrual cycles pre- and post-treatment) and PMDD-related psychological and functional impairment (retrospective ratings). Participants in the treatment group (vs waiting list) are expected to report a reduction in primary outcomes during the luteal (premenstrual) phase after treatment (vs baseline). No group differences in outcomes are expected during the follicular (post-menstrual) phase.

Secondary outcomes include treatment effects on quality of life (QoL) and difficulties in emotion regulation. Participants in the treatment group are expected to report higher QoL and lower levels of difficulties in emotion regulation after treatment (vs. baseline) than the waitlist control group. To assess long-term treatment effects, follow-up assessments will be conducted 6 and 12 months after treatment.

Health economic data will be collected for future health economic evaluations of the treatment.

Analysis

All randomised participants will be included in the intention-to-treat (ITT) population, regardless of whether they received or completed treatment. The per-protocol (PP) population will be a subgroup of the ITT population containing all participants without a major protocol violation. Sensitivity analyses will also be conducted with (1) participants who have completed at least four mandatory modules (modules 1-4) and (2) participants who have completed at least four mandatory modules and at least one of the optional lifestyle modules. To further explore potential differential effects of ICBT, exploratory analyses will be conducted for different symptom clusters (e.g., affective symptoms) and symptom trajectories in terms of onset and/or in combination with severity and severity peak. The relationship between difficulties in emotion regulation and improvement in primary outcomes will also be explored.

• Group differences in quality of life during the luteal phase from baseline to post-treatment [Срок оценки: Baseline to post-treatment (first luteal phase after treatment, i.e., 8-10 weeks after baseline). Follow-up assessments at 6 and 12 months post-treatment. All assessements will be collected during luteal phase.]
• Group differences in difficulties in emotion regulation during the luteal phase from baseline to post-treatment. [Срок оценки: Baseline to post-treatment (first luteal phase after treatment, i.e., 8-10 weeks after baseline). Follow-up assessments at 6 and 12 months post-treatment. All assessements will be collected during luteal phase.]
• Group differences in health-related quality of life during the luteal phase from baseline to post-treatment [Срок оценки: Baseline to post-treatment (first luteal phase after treatment, i.e., 8-10 weeks after baseline). Follow-up assessments at 6 and 12 months post-treatment. All assessements will be collected during luteal phase.]
• Remission (Full/Partial) [Срок оценки: Post-treatment (daily ratings over two menstrual cycles [ca 56 days] starting 8 weeks after baseline). Follow-up assessments at 6 and 12 months post-treatment (daily ratings one cycle [ca 28 days] beginning 6 and 12 months post-treatment).]