1. Introduction
oday, one of the necessary measures to optimize education in a country is examining the effective factors on the academic growth and motivation for achievement in university students [1]. Academic procrastination is delaying the tasks and activities associated with studying. It is one of the significant factors related to students’ academic performance and neglecting it could bring about irredeemable repercussions [2]. According to Molen, procrastination is frequent among students [3] as its prevalence ranges from at least 71%-91%; its acute kind has been estimated to range from 23%-31% [4]. Academic procrastination is effective in preparing for exams, doing homework, and attending class sessions [5]. It influences mental health and academic achievement in university students and its most crucial outcome is academic underachievement [12]. 
Because of its cognitive nature, proper psychological interventions could presumably prevent academic procrastination and underachievement. There are several therapeutic interventions for academic procrastination, including cognitive behavioral therapy which has had the most application, and many studies have been devoted to it [13, 14, 15, 16]. In this regard, some studies [20, 21, 22] considered the effectiveness of third-wave therapies; however, more studies are required to determine the clinical effectiveness of these therapies as they are new-found. We could point out Acceptance and Commitment Therapy (ACT) among the interventions. 
Some mental factors such as stress, depression, and anxiety can also intensify academic underachievement and procrastination in university students. Studies have shown that ACT is effective in reducing stress, anxiety, depression, and cognitive dissonance. Thus it seems that this therapy could reduce academic procrastination and as a result underachi,evement in university students. Moreover, studies investigating the procrastination of students of Zanjan University of Medical Sciences showed that these factors have spread among the students [29, 30, 31]. Therefore, the purpose of this study is to determine the effectiveness of ACT in reducing the academic procrastination of students at Zanjan University of Medical Sciences. 
2. Methods 
The present interventional and quasi-experimental study was done with a pre-test-post-test design and a control group. All of the questionnaires were completed by the subjects in the pre-test phase. Furthermore, the study variables for the intervention group and the control group were calculated in both pre-test and post-test to determine and compare the effectiveness of the intervention. The study population included all 90 students reported with academic underachievement to the Zanjan University of Medical Sciences counseling office in the 2017-2018 academic year. Thirty-eight students were included in the study in two groups of 19 members by the purposive method. The researcher and data coding method was used in all stages of the study to prevent sample pollution. There were no sample losses in both groups after the final selection. The inclusion criteria were a GPA of less than 12 in the semester (conditional pass), a higher grade than the cut-off point allotted in the procrastination questionnaire and exclusion criteria consisted of psychotic disorders, personality disorders, depression, anxiety, and structured clinical interview based on SCID_I (Structured Clinical Interview for DSM-IV Axis I Disorders) to assure the absence of other problems such as depression in subjects in the first stages of screening. 
3. Results 
Thirty-eight students with high academic procrastination participated in this study. Female students were most frequent in both groups. There were 14 and 15 female students in the intervention group and control group, respectively. The most frequent age range was 18-21 years and the most frequent participating subjects were medical students in both groups. Moreover, the F coefficient related to the group factor in academic procrastination was 257.553 and statistically significant (P<0.05) level in post-test and MANCOVA test. Therefore, the hypothesis of the effectiveness of ACT on procrastination and its components was confirmed. Besides, the significance of the F effect of the pre-test showed that the sensitization of the pre-test had a decreasing or increasing effect on the experimental intervention (Table 1). 



4. Discussion 
Academic procrastination and underachievement include different aspects, one of the important and significant of which is psychological factors. Accordingly, the study of such factors needs to be multi-dimensional and comprehensive. In addition to education, cultural and student domains and counseling have active roles in solving the problems of students with academic underachievement. This process indicates the significance of psychological factors in the underachievement of university students. Constant and accurate use of psychological approaches should be incorporated in solving these issues. The results of this study confirmed this conclusion. The results showed the favorable effects of psychotherapies, particularly ACT. Furthermore, given the prevalence of procrastination and underachievement among university students, the results of this study could be effective in reducing the factors. 
Ethical Considerations
Compliance with ethical guidelines
This study is confirmed ethically by the registration ID IR.ZUMS.REC.1937.394. All ethical principles were observed in this study. The participants had the right to withdraw from the research at their will. Also, all of the information associated with participants were kept confidential during the research process. 
Funding
This research was funded by the National Agency for Strategic Research in Medical Education, Tehran, Iran with a registration number of 961073. 
Authors contributions
Conceptualization: Ehsan Fakour and Alireza Armani Kian; Research: Bahram Rostami, Mehdi Maqbooli, Ehsan Fakour; Editing and finalizing: Seyedeh Elnaz Mousavi.
Conflicts of interest
The authors declared no conflicts of interest. 
Acknowledgements
The authors of this article would like to thank the management and colleagues at the National Agency for Strategic Research in Medical Education and all of the participating students in this research.