Introduction 
Problematic pornography use (PPU) refers to excessive use of pornography and continuing its use despite its harmful social, psychological, physical, sexual, family, and economic consequences, and is associated with symptoms such as compulsive behaviors, uncontrollable cravings, and searching behaviors [6]. One of the important and fundamental issues in PPU is the craving phenomenon. Craving is a strong and immediate desire for something that may eliminate the possibility of focusing on other things [7]. One of the major issues in people with PPU is the inability to accept the negative emotions resulted from this phenomenon, such as shame and low cognitive flexibility [8]. Acceptance and commitment therapy (ACT) is one of the proposed evidence-based treatments for behavioral addictions, including PPU [9]. High levels of neuropsychological deficits are associated with behavioral addictions. Abnormalities in executive functions have also been reported, which are related to some biological factors [11]. 
One the therapeutic methods to regulate the dorsolateral prefrontal cortex (DLPFC) and reduce craving and neuropsychological deficits is transcranial direct current stimulation (tDCS) [13]. Most of recent studies have focused on psychological and neurological factors related to the PPU, and no research has been conducted directly on this type of behavioral addiction. Therefore, this study aims to investigate the effectiveness of combining ACT with tDCS in reducing craving and PPU in men. Hypotheses were:
ACT significantly reduces craving and PPU;
tDCS significantly reduces craving and PPU;
Combination of tDCS with ACT causes a significant reduction in craving and PPU.
Effects of combined treatment on the reduction of craving and PPU are greater than those of tDCS and ACT.

Method
This is a quasi-experimental study with a pre-test/pos-test/follow-up design. The study population includes all men aged 18-24 in 2022 referred to the specialized counseling centers of Ferdowsi University of Mashhad and diagnosed with PPU by a clinical psychology specialist. Of these, 9 eligible men were selected purposefully. They were placed in three experimental groups using the computerized random number generator in SAS and sequentially numbered, opaque, sealed envelopes (SNOSE) to preserve random allocation concealment. The entry criteria were age 18-24 years, no intellectual problems, at least elementary school education, no drug abuse, having symptoms of PPU based on the questionnaire, and not receiving other psychological or drug treatment at the same time. Exclusion criteria were diagnosis of mental disorders that affect the treatment process, simultaneous participation in other psychological interventions, absence from more than three consecutive sessions, and unwillingness to continue participation in the study.

Results
Figure 1 shows the changes in craving and PPU in men no. 1, 2 and 3 (ACT group) at the pre-test, post-test, and follow-up phases, based on a visual assessment. As can be seen, in both craving and PPU decreased after intervention in all three subjects compared to baseline, and this decrease continued in the follow-up period.
Figure 2 shows the changes in PPU and craving in subjects No. 4, 5 and 6 (tDCS group) at the pre-test, post-test, and follow-up phases, based on the visual evaluation. As can be seen, there was a decrease in both variables after the intervention, compared to the baseline, and this decrease continued in the follow-up period; the slope of the decrease in the post-test phase was similar to that in the follow-up phase.
Figure 3 shows the changes in craving and PPU of subjects no. 7, 8 and 9 (in combined group) at the pre-test, post-test, and follow-up phases. As can be seen, there was a decrease in both variables after the intervention compared to the baseline, and this decrease continued in the follow-up phase.
According to the percentage of non-overlapping data (PND) for combined treatment, ACT and tDCS, it can be said that the combined treatment resulted in significantly greater reduction in craving and PPU compared to ACT and tDCS. In addition, ACT resulted in significantly greater reduction in craving and PPU than tDCS.

Conclusions
The results obtained from the first group showed that ACT and tDCS are effective in reducing craving and PPU. This is consistent with the results of Twohig and Crosby, Crosby, and Fraumeni-McBride [9, 10, 18]. Inhibitory control is a type of executive function that is related to the DLPFC area, responsible for processing information during the presence of emotional stimuli [13]. Therefore, it can be concluded that stimulation of the DLPFC can have an effect on the inhibitory control of emotional stimuli and reduce the craving and use of pornography. In general, the results of the present study showed that the ACT and tDCS alone or in combination with each other had significant effects on reducing craving and PPU in men, where the combined treatment was more effective.
The main limitation of this study was the low sample size and the use of a single-subject design. In addition, caution should be exercised in generalizing the results to other patients in Iran. The samples were male only. The follow-up duration was only one month. The tools used in the present study were self-report tools which may cause biased responses. Since there is a high comorbidity of PPU with psychological disorders, such as depression and anxiety, it is recommended to pay attention to transdiagnostic factors to achieve the desired effectiveness in a shorter time. 

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of Ferdowsi University of Mashhad (Code: IR.UM.REC.1400.12) and was registered by the Iranian Registry of Clinical Trials (ID: IRCT20190731044397N1).

Funding
This article was extracted from the PhD thesis of Seyed Iman Seyedzadeh Dalooyia registered by the Faculty of Educational Sciences and Psychology, Ferdowsi University of Mashhad. This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

Authors contributions
Author Contributions: Conceptualization, Seyed Iman Seyedzadeh Dalooyi; Methodology, Mohammad Saeed Abdekhodaei; Investigation, all authors; Writing  Original Draft, Seyed Iman Seyedzadeh Dalooyi; Writing  Review & Editing, Hamidreza Aghamohammadian Sharbaaf; Resources, Ali Ghanaei Chamanabad; Supervision, Hamidreza Aghamohammadian Sharbaaf; Funding Acquisition, all authors.

Conflicts of interest
The authors declare no conflict of interest

Acknowledgments
The authors would like to thank all participants for their cooperation in this study. 



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