BACKGROUND: Premenstrual syndrome (PMS) is a common problem of women of reproductive age, affecting various aspects of their lives. However, limited studies have investigated the effect of internet-based cognitive-behavioral therapy (ICBT) on PMS. Therefore, we aimed to assess whether ICBT can reduce symptom severity of women with PMS and improve their quality of life during the perimenstrual and late follicular phases of menstrual cycle. METHODS: The study included 92 university students aged 18–35 years who had moderate to severe PMS. The participants were allocated into two groups of 46 using block randomization. The intervention group underwent ICBT for two menstrual cycles, while the control group received no intervention. Before and after the intervention, all participants filled the Daily Record of Severity of Problems (DRSP) for two menstrual cycles 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. Data were analyzed using univariate general linear models. RESULTS: Four students in the intervention group were lost to follow-up. Following the intervention, the mean score of total PMS symptoms was significantly lower in the intervention group than in the control group (10.4 vs. 20.2, adjusted difference: − 9.9 [95% CI − 13.3 to − 6.6]), and the score of perimenstrual quality of life was significantly higher (64.2 vs. 50.3, 14.1 [8.5 to 19.8]). However, there was no significant intergroup difference in the late follicular quality of life (68.3 vs. 67.3, 1.9 [− 4.4 to 8.1]). CONCLUSIONS: The ICBT could reduce the symptom severity of women suffering from PMS while improving their perimenstrual quality of life. However, it had no significant effect on the late follicular quality of life. Therefore, this intervention can be used for women with PMS. Trial registration The Iranian Registry of Clinical Trials, Identifier: IRCT20100414003706N34, Registered prospectively on 19 June 2019, https://www.irct.ir/trial/38394. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12905-021-01589-7.
Internet-based cognitive-behavioral therapy for premenstrual syndrome: a randomized controlled trial