Researchers in Sweden are preparing to test a new online therapy program designed specifically for people with PMDD. The treatment combines cognitive behavioral therapy (CBT) — a well-established talk therapy approach — with skills for managing intense emotions and improving relationships, borrowed from a therapy called dialectical behavioral therapy (DBT). The entire program is delivered over the internet with therapist support over 8 weeks, which could make it much more accessible than traditional in-person therapy.
Why does this matter for people with PMDD? While medications like SSRIs are often helpful, many people either don't respond fully, experience bothersome side effects, or simply prefer not to take them. CBT has shown promise for reducing premenstrual symptoms, but researchers believe it could work even better if it specifically teaches skills for handling the emotional storms and relationship conflicts that are among the most distressing parts of PMDD. This new program directly targets those challenges with modules on emotion regulation, mindfulness, distress tolerance, and interpersonal effectiveness.
The trial plans to include 164 people with confirmed PMDD diagnoses, all verified through daily symptom tracking over two full menstrual cycles — a rigorous approach that helps ensure participants truly have PMDD rather than other conditions. Half will receive the online therapy while the other half will initially be placed on a waiting list (and offered treatment afterward). The researchers will also be the first to study whether this kind of therapy is cost-effective, which matters for making it widely available through healthcare systems.
It's important to note that this paper describes the plan for the study — results won't be available until around 2028. However, it builds on a similar German study that showed medium to large improvements in PMDD symptoms and daily functioning. If this trial confirms those findings, it could mean a new, accessible treatment option for people who need alternatives or additions to medication.
Key findings
- This is a study protocol; no results are reported yet. The trial plans to enroll N=164 participants with DSM-5-confirmed PMDD, randomized 1:1 to 8 weeks of therapist-guided ICBT or waitlist control.
- The ICBT intervention incorporates DBT-derived emotion regulation and interpersonal effectiveness skills training alongside traditional CBT components, which is a novel adaptation for PMDD treatment.
- PMDD diagnosis will be established using prospective daily symptom ratings over two menstrual cycles scored with the C-PASS algorithm, considered the gold standard diagnostic approach.
- Power analysis was based on a medium effect size (Cohen's d=0.5) with 80% power, adjusted for 25% expected attrition, yielding N=164 total.
- A prior German RCT of ICBT for PMDD using a similar (but not identical) protocol reported medium to large effect sizes on symptom intensity (f²=0.13), impact on everyday life (f²=0.12), and psychological (f²=0.20) and functional impairment (f²=0.26).
- The trial will include a health economic evaluation (cost-effectiveness and cost-utility analyses), which would be the first for any psychological intervention for PMDD.
Methods, briefly
Parallel two-group RCT with 1:1 allocation. Planned N=164 adults (ages 18–45) with DSM-5-confirmed PMDD (diagnosed via C-PASS algorithm using prospective daily ratings over 2 menstrual cycles). Eight weeks of therapist-guided ICBT versus waitlist control. Primary outcomes: change in daily PMDD symptoms/impact (DRSP) and psychological/functional impairment (PMS-I). Secondary outcomes: quality of life (BBQ) and emotion regulation difficulties (DERS-16). Follow-ups at 6 and 12 months. Data analyzed using latent Gaussian process modeling and linear mixed models. Includes health economic evaluation. Recruitment anticipated February 2025, completion February 2028. Conducted in Sweden.
Limitations to keep in mind
- This is a study protocol only — no results are available yet.
- Waitlist control design limits conclusions about treatment-specific effects versus non-specific effects (e.g., therapist attention, expectancy).
- No comparison group for 6-month and 12-month follow-ups since waitlist receives treatment after post-assessment.
- Participants must be proficient in Swedish, limiting generalizability to other populations.
- Participants on stable pharmacological treatment are included, which enhances generalizability but may complicate interpretation of ICBT-specific effects.
- Self-report measures are used for most outcomes.
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