Study design and participants
This randomized controlled trial was approved by the Ethics Committee of Tabriz University of Medical Sciences with the approval code of IR.TBZMED.REC.1398.014 and was registered at the Iranian Registry of Clinical Trials with the registration code of IRCT20100414003706N34. Participant recruitment was then conducted. We followed the CONSORT guidelines.
The inclusion criteria were healthy university students aged 18–35 years who lived in the residence halls of the Tabriz University of Medical Sciences (4 residence halls with approximately 1200 students), had a regular menstrual cycle duration of 25–35 days in the past 6 months, had moderate to severe PMS symptoms diagnosed using prospective Daily Record of Severity of Problem (DRSP) for 2 menstrual cycles, and did not currently use treatment for PMS or Premenstrual Dysphoric Disorder (PMDD).
Exclusion criteria included professional athletes; pregnant and postpartum women (within 1 year of delivery); women who were breastfeeding their babies; individuals with current major depression; students with a history of a major psychiatric disorder, including psychosis, bipolar disorder, eating disorder, and severe depression; persons with a history of drug, alcohol, or hookah use within the past two years; patients who had taken antidepressants, benzodiazepines, anticancer drugs, oral contraceptives, or hormones in the past three months; individuals who were affected by diseases such as gastrointestinal, cardiovascular, renal, and endocrine disorders or epilepsy; students who had experienced a highly stressful event such as parental divorce or death of a first-degree family member in the past six months; those with gynecological problems such as previous hysterectomy, oophorectomy, gynecological cancer, polycystic ovary syndrome, endometriosis, and infertility; students with no access to Internet; or those who did not have an e-mail account or phone number.
All exclusion criteria were applied based on the personal reports of the participants, except for major depression, which was assessed using the Beck questionnaire and the DRSP. We also attempted to include students living in two private residence halls (approximately 225 students). However, there was no cooperation from those in charge. Therefore, we excluded these students.
We considered a sample size of 92 (n = 46 for each group) based on PMS scores from a previous study conducted in a similar study setting (M1 = 163.6, SD1 = 89.5) , with an estimated 35% reduction in mean PMS score by the intervention (M2 = 106.3, SD2 = SD1), two-sided α = 0.05, power = 80%, and 15% probability of loss to follow-up. This sample size was sufficient to meet other study objectives with a power greater than 80%.
Recruitment & Randomization
First, potential participants selected using a checklist of initial eligibility criteria completed the sociodemographic and reproductive questionnaire and a validated Persian version of the 19-item Premenstrual Symptoms Screening Tool (PSST) . According to the PSST developers , PMS screening is positive when the woman reports at least five of 14 PMS symptoms. The reported symptoms must be moderate or severe, and at least one of them must be one of the four main PMS symptoms. In addition, the symptoms must moderately to severely interfere with at least one of the five domains of life.
Participants gave written informed consent. Then, those with positive PMS screening were asked to complete the DRSP during a menstrual cycle. In addition, they were asked to complete the validated Persian version of the 21-item Beck Depression Inventory  on one of the days after the menstruation end and before the first day of the estimated luteal phase. The participants with a score of 29 or higher on the Beck questionnaire  were diagnosed with major depression and subsequently excluded from the study. The remaining participants were asked to complete the DRSP during a second menstrual cycle, as well as the Sheehan Disability Scale (SDS) and the Menstrual Attitude Questionnaire (MAQ) on day 1–2 of menstruation and the Quality of Life Enjoyment and Satisfaction Questionnaire - Short Form (Q-LES-Q-SF) on days 1–2 and 11–13 of the menstrual cycle. Participants with symptoms of major depression in the follicular phase based on the 2-cycle DRSP were also excluded.
The female students with moderate to severe PMS, diagnosed based on the DRSP, were finally included in the study. They were randomly allocated into the intervention and control groups using the block randomization method. Allocation sequence was generated with randomly varied block sizes of four and six and an allocation ratio of 1:1 using an online program (www.random.org). The sequence generation was performed by an individual who was not involved in participant recruitment and data collection. In addition, the central telephone method was used for allocation concealment, while participant recruitment was done by the first author (SB).
Only one eligible participant was recruited from each room in the residence hall (each room usually had 3–6 students) to prevent contamination. Approximately 20% of participants were not present in the residence hall during most of the intervention period because it was semester break or the university was closed due to the COVID − 19 pandemic.
The research team developed educational content for 8 sessions (one session per week) by reviewing all the literature and using the intervention content of the previous study in this field  and the comments of some experts in reproductive health and psychology. The sessions' contents were mainly focused on the intervention content of the previous study in Germany . For example, the general information on PMS/PMDD and the etiology were presented in the first session, while the last session included the instructions for the patients, such as the methods for relapse prevention. Both the cognitive and behavioral strategies were discussed in sessions 2, 3, 4, 5, 6, and 7. The cognitive strategies discussed in the sessions were as follows:
Session 2: Psychological training on the role of thoughts and their relationship with emotions and behavior (cognitive triangle)
Session 3: Changing to the certain topic of PMS
Session 4: Reconstruction of dysfunctional perceptions
Session 5: Psychological training on specific superstitions about PMS and application of the cognitive strategies learned
Session 6: Psychological training on effective thoughts and developing new assessments
Session 7: Certain behaviors to improve PMS (use of healthcare, seeking support, and communication)
Moreover, the behavioral strategies discussed in the sessions were the following subjects:
Session 2: Psychological training on the relationship between stress and PMS and teaching relaxation techniques
Session 3: Psychological training on the interdependence between nutrition, exercise, and PMS
Session 4: How to integrate exercise into daily life using a motivational program and strategy
Session 5: What is a balanced diet and how to follow it in the daily life
Session 6: Psychological training on the impact of stress-related errors on reasoning
Session 7: Training on participating in positive activities in daily life
The participants were provided with audiovisual material to facilitate learning practical exercises such as relaxation techniques, exercises related to thought change, and physical exercises, including yoga.
When the educational content was prepared, the principal investigator (SB) designed a counseling course in the Learning Management System (LMS) website of the Tabriz University of Medical Sciences (Modular Object-Oriented Dynamic Learning Environment (MOODLE), https://moodle.org). The course was designed under the supervision of the person in charge (AA) of the university LMS website.
Special accounts were created for each member of the intervention group, and the account information was sent to them via E-mail, SMS, and one of the social media platforms they used. The intervention group received the contents in a scheduled manner. When a piece of content was loaded on the website, the participants received an e-mail or SMS. In addition, we created a telegram channel for them, through which we sent them daily reminders to visit the website and receive the educational content. In addition, participants were instructed how to use the LMS website before the course, and those who did not log in to their account within the first week of the course were reminded by telephone. Also, they could ask questions online and receive answers from the principal investigator (SB).
In order to check the treatment adherence, the participants were assigned homework at the end of each session and were supposed to submit their weekly feedback using the website or social media platforms. The participants with delays in sending feedback were reminded via SMS. In case of no answer, we called them by phone. Also, they received calls from the principal investigator every two weeks to keep them motivated. In these calls, the principal investigator discussed the strategies with the participants, asked about the effectiveness of the strategies for them, received the suggestions and criticisms, asked them to write their questions using the LMS website, and answered the questions.
The control group did not receive any intervention during the study period. When all post-test assessments were done, the accounts of the control group were created, and they received the intervention.
Data collection tools
We used the following tools to evaluate the severity of PMS symptoms and quality of life of the participants (primary outcomes), as well as the PMS-related disability and attitude toward menstruation (secondary outcomes):
Researcher-made demographic and gynecologic questionnaire
The questionnaire was prepared by reviewing the literature in this field and included three parts: demographics, contact information, and gynecologic information, including menstrual history. The face and content validity of the questionnaire was determined by 10 experts in this field.
Daily Record of Severity of Problems (DRSP)
This scale is a valid scale widely used for PMS diagnosis and is consisted of 21 items on 11 domains of PMS symptoms, including depression, anxiety, mood lability, anger, interest, concentration, lethargy, appetite, sleep, overwhelm, physical symptoms, and 3 impairment items. Each item is scored on a scale of 1 (not at all) to 6 (extreme) . The questionnaire must be completed for at least two consecutive cycles. A PMS diagnosis is made if a person has a score of 4 (moderate) or higher in 5 or more of the symptoms for at least 2 days in the late luteal phase (days − 5 to -1 of the menstrual cycle). The score of 4 or higher should be in at least one of the items assessing depression, anxiety, affective lability, or anger/irritability, and in at least one of the 3 impairment items. However, she must not have a mean score higher than 3 (mild) in any of the symptoms during the mid-follicular phase (days + 6 to + 10 of the menstrual cycle) .
In a study by Ozgoli et al., the internal consistency of the Persian version of this scale was good (Cronbach's alpha = 0.80) . In the present study, the reliability of the scale was also confirmed, with a Cronbach's alpha equal to 0.97 for the total scale and 0.82–0.91 for the domains. In addition, the test-retest agreement was good for the total DRSP [intraclass correlation coefficient (ICC) = 0.815, 95% CI: 0.720 to 0.878].
Quality of Life Enjoyment and Satisfaction Questionnaire – short form (Q-LES-Q-SF)
This unidimensional tool includes 14 items scored on a five-point Likert scale (very poor, poor, fair, good, and very good) and assesses the quality of life during the last week. Higher scores indicate higher quality of life. The reliability of the Persian version of this questionnaire has been confirmed on the university students in Kashan (ICC = 0.97–0.98, Cronbach's alpha = 0.93)  and Tabriz (Cronbach's alpha = 0.887–0.937) .
The women suffering from PMS have different levels of quality of life in perimenstrual compared to late follicular period . Therefore, the participants filled the questionnaire twice, once at days 1–2 and once at days 11–13 of the menstrual cycle. The internal consistency of the scale was good for both assessments (Cronbach's alpha = 0.86 and 0.85, respectively). The test-retest agreement (between the two pre-intervention assessments) was good as well (ICC = 0.783, 95% CI; 0.672 to 0.856).
Sheehan Disability Scale (SDS)
This questionnaire is a self-report scale on disability and dysfunction  that evaluated the disturbances in 3 areas of work/school, social life, and family life/home responsibilities using a 0–10 visual analogue scale . In the present study, we combined the scores of these 3 areas to obtain a total SDS score . The Persian version of the scale has good internal consistency (Cronbach's alpha = 0.88) . Its reliability in the present study was confirmed as well (Cronbach's alpha = 0.67).
Menstrual Attitude Questionnaire (MAQ)
This questionnaire includes 33 items in 5 domains, with 5–7 items in each domain. The items are scored on a 7-point Likert scale (from "strongly disagree" to "strongly agree"), with some items with negative concepts being reversely scored . In the present study, the internal consistency was confirmed for all domains (Cronbach's alpha = 0.66–0.83, menstruation as a debilitating event = 0.82, menstruation as a bothersome event = 0.79, menstruation as a natural event = 0.83, anticipation and prediction of the onset of menstruation = 0.66, denial of any effect of menstruation = 0.66)
Participant satisfaction and views on intervention effectiveness
The satisfaction of participants with the intervention was assessed using a question scored on a 5-point Likert scale (from "very satisfied" to "very dissatisfied"), while their opinions on the effectiveness of intervention were assessed using another question scored on a 6-point Likert scale (from "not at all" to "very high").
Pre-intervention assessments are already described in the sub-section of "participant recruitment." Following the two month intervention duration, all participants started to complete the DRSP for the next two cycles. Also, they completed the Q-LES-Q-SF, SDS, and MAQ in month 3 after the allocation, at the same times of the menstrual cycle the pre-test questionnaires were filled. At the end of the intervention period, the intervention group reported their satisfaction levels with the intervention and their opinions on its effectiveness. Most questionnaires were filled online by the participants for higher accessibility.
Data analysis was performed using the SPSS version 25. The normality of the quantitative variables' distribution was confirmed using the one-sample Kolmogorov-Smirnov test by group. In order to evaluate the effect of the intervention, univariate general linear models were used for intergroup comparisons of the post-intervention assessment values, which were adjusted for the baseline values. α = 0.017 was considered the significance level for the three primary outcomes because the multiple comparisons were corrected using the Bonferroni correction method, while α = 0.05 was considered the significance level for other comparisons. We used the modified intention-to-treat (ITT) analysis while excluding the four participants lost to follow-up.