1. Introduction
Iranian society is a young society because more than 33% of its population comprised of young people. Of these, eligible males enters the military service according to the laws and in order to protect the Islamic Republic System. Entering the military service leads to major changes in individual, family and social life of people, and is a sensitive period. This period is associated with a lot of stress caused by separation from family and loved ones, changes in dietary habits, restrictions on freedom of choice and action, high and imposed discipline, frequent and forced relocation, changes in sleeping habits, performance anxiety on expectations, fear of having a relationship with others, and inability to resolve problems properly.
Suicide exists in all age groups, but it is more common among young people, especially conscripts, due to their specific situations. According to the World Health Organization, about 800,000 people commit suicide worldwide each year, and it was predicted that this figure would reach 1.5 million people a year by 2020. Nosratabadi et al. found that 28.4% of conscripts are at a high risk of suicidal ideation [8]. Depression is the most important and well-known predictor of suicidal ideation and suicide attempt. Depressed people who commit suicide believe that there is no hope for their future. Hopelessness is an important cause of suicide attempt in depressed people. Cognitive factors such as negativism and hopelessness along with a pessimistic view of the future, belief in disability and inadequacy, and social isolation can increase one’s vulnerability to depression and suicide.
One of the effective approaches in the treatment of depression is Acceptance and Commitment Therapy (ACT), which was introduced by Hayes et al. in the early 1980. The main purpose of ACT is to increase cognitive flexibility through six core processes of acceptance, cognitive defusion, self as context, ‎contact with ‎the present moment, values, and committed action. Cognitive flexibility is a major characteristic of human cognition and refers to one’s ability to simultaneously consider the two conflicting aspects of an object or event. Given the effectiveness of ACT in patients with a variety of psychological disorders, it seems to improve cognitive flexibility and thus reduce suicidal ideation, depression, and hopelessness in conscripts. Therefore, the present study aims to evaluate the effect of ACT group therapy on suicidal ideation, depression, hopelessness and cognitive flexibility among conscripts.
2. Methods
This is a clinical trial ‎with a pretest/posttest design using a ‎control group. The study population consisted of all depressed conscripts referred to military counseling centers in Khorasan Razavi Province of Iran. Of these, 60 conscripts who met the inclusion criteria were randomly selected and assigned into two groups of intervention (n=30) and control (n=30), using a convenience sampling method. The data collection tools were the Beck Scale for Suicidal Ideation, Beck Hopelessness Scale, Beck Depression Inventory-II, and Cognitive Flexibility Inventory. The intervention group received ACT at eight 90-minute sessions, while the control group received no intervention and remained on the waiting list. To analyze the collected data, one-way Analysis of Covariance (ANCOVA) was used in SPSS v. 24 software.
3. Results
Depression, suicidal ideation and hopelessness scores of both groups were very high in the pretest phase. The scores of these variables changed reduced in the intervention group after treatment. The results of ANCOVA comparing the two groups after removing the pretest effects are presented in Table 1.


The results revealed that ACT group therapy caused a significant decrease in suicidal ideation, depression and hopelessness, and a significant increase in cognitive flexibility and its components.
4. Discussion
Based on the results of the current study, suicidal ideation, depression and hopelessness in conscripts were significantly reduced compared to controls after ACT, and their cognitive flexibility and its components (control perception, different options perception, and behavior justification perception) improved significantly. Several studies using the ACT have shown that this intervention leads to the development of cognitive flexibility in people suffering from depression, resulting in changes in their life expectancy and quality of life. The goal of ACT is to increase the patients’ ability to connect with their present and be at the moment. Mindfulness and connection with the present (as opposed to overcoming the conceptualized past and future) which lead to cognitive flexibility, can help people get rid of disturbed thoughts, habits and unhealthy behavior patterns and thus play a crucial role in regulating behaviors and reducing depression, suicidal ideation, and hopelessness. People with cognitive flexibility does not avoid unwanted events and does not attempt to control or modify them. They put their energy on values and quality of life instead of avoiding unwanted events. 
Overall, it can be concluded that ACT group therapy, through mindfulness training and use of experiential exercises and metaphors, leads to increased cognitive flexibility and individual commitment to perform meaningful actions based on individual values, and ultimately decreases depression, suicidal ideation and hopelessness in conscripts.

Ethical Considerations
Compliance with ethical guidelines
All participants signed a written informed consent form prior to study and they were assured that their information would remain completely confidential. This study obtained its ethical approval from the Ethics Committee of Hakim Sabzevari University (Code: IR.HSU.REC.1398.016) in Iran and registered by Iranian Registry of Clinical Trial (Code: IRCT 20180218038786N2).

Funding
This study was funded by the Deputy for Research of Hakim Sabzevari University, Sabzevar, Iran.

Authors contributions
Conceptualization: Hossein Shareh; Methodology: Hossein Shara, Validation: Hossein Shara, Zahra Robati; Research: Hossein Shareh and Zahra Robati; Sources: Hossein Shareh and Zahra Robati; Drafting: Zahra Robati; Editing and finalizing By: Hossein Shareh; Visualization: Hossein Shareh, Zahra Robati; Supervision: Hossein Shareh; Project Management: Hossein Shareh.

Conflicts of interest
The authors declare no conflict of interest.

Acknowledgements
The authors would like to thank‎ the managers, physicians and personnel of military counseling centers in Khorasan Razavi Province for cooperation, and all the conscripts who participated in the study.


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