Breast cancer remains the second leading cause of cancer death worldwide and the leading cause of cancer death in women. It accounts for around 21% of all cancers. 1 The breast is an important part of a woman's body image; thus, any abnormality in this area can lead to cognitive problems for women. 2 The disease-induced clinical symptoms lead to high perceived stress, and impede socio-individual relationships and adjustment. 3 Women with breast cancer may experience boredom, sadness, hopelessness, discouragement, loneliness, and dissatisfaction. 4 Perceived stress is a common problem in these women. 5 The high perceived stress in these women influences their mental state during the disease. 6 Studies suggest that stress involves physical, mental, and emotional reactions experienced as a result of changes in the needs of a person's life. These major or minor changes could disturb patients. Perceived stress impairs a person's perceived ability and confidence in the face of stress and leads to mood problems. 78 Women with breast cancer develop metacognitive beliefs due to their suffering which threatens their mental health. 9 Metacognitive beliefs cause disorders that affect their thinking style and adaptability, 10 making them anxious and worried. To cope with anxiety, patients usually resort to metacognitive beliefs. Metacognitive beliefs and unwanted or disturbing thoughts are the main problem of patients with special diseases, because they permanently experience threat and negative emotions. According to psychologists, this coping style is inefficient and incompatible as it fails to solve problems and exacerbates psychological and mood disorders. 11 On the other hand, these patients experience high levels of death anxiety due to the cancer-induced stress and fear. Death anxiety disturbs the mental balance of patients. Cancer induces death anxiety more than other diseases due to its specific conditions. 12 Death anxiety is closely related to the underlying fear associated with the destruction of a person's life. It includes overt or covert horror elements in various degrees. Perceived stress affects the degree of death anxiety. Major cognitive components of death anxiety include attitudes, conceptual ability to predict and expect the future, and open awareness of dying. 1314 Women with breast cancer suffer high levels of stress due to their disease-induced emotional, cognitive, behavioral and physical problems which increase their metacognitive beliefs, death anxiety, and rumination, disrupt the treatment process, and exert a negative impact. Due to the specific condition of breast cancer patients, there is a concern about what treatment is more effective in reducing stress and rumination in them as they disturb quality of life and increase death anxiety in patients. There is a need to increase their quality of life and improve their cognitive status using the best educational approach. 151617 Positive thinking training helps individuals identify their positive experience in coping with hardships and strengthens their self-respect and self-esteem, thus boosting their well-being and resistance to stress, reducing their rumination and anxiety, and establishing peace and hope in these patients. 1819 Positive psychology is the scientific study of human flourishing and strength. Positive thinking training plays a major role in human flourishing and optimal functioning. 20 It applies theories, studies, and psychological intervention techniques to identify the components of satisfactory, adaptive, creative, and emotional human behavior. It is the scientific study of human experiences, positive traits and institutions that facilitate changes in individuals. 2021 Positive thinking training may exert positive effects on controlling perceived stress, metacognitive beliefs and death anxiety in patients with breast cancer. 10 Studies suggest that this training has a significant effect on reducing stress and cognitive problems. 22 Research shows that positive thinking training has a significant effect on reducing perceived stress and symptoms of stress, improving metacognitive beliefs, and reducing death anxiety in women with breast cancer. 2324 Given the severity of the breast cancer symptoms and the high degree of disability, researchers and therapists have always sought to find the best effective ways to reduce the physical and psychological symptoms of women with breast cancer, on the one hand, and increase their ability, on the other. It is important for therapists to find out what treatment is more effective in the short term. In recent years, the role of psychological factors in diseases has been taken into account. An effective protocol should be identified to reduce perceived stress, metacognitive beliefs, and death anxiety in women with breast cancer. The study of a therapeutic intervention that balances stress episodes in these women and improves their metacognitive beliefs and death anxiety could promote their quality of life and be a major help to these patients and medical centers and improve their perceived stress, metacognitive beliefs, and death anxiety. Given the paucity of studies on the effect of positive thinking training on psychological variables in women with breast cancer, this study aimed to investigate the effectiveness of positive thinking training on perceived stress, metacognitive beliefs, and death anxiety in women with breast cancer.

This was a quasi-experimental study with pretestposttest control group design. Statistical population consisted of all women with breast cancer visiting Shafa Health Center of Ahvaz in 2019. In this study, 30 women with breast cancer were selected using convenience sampling. Breast cancer patients were randomly divided into intervention (n=15) and control (n=15) groups. In the present study the specified sample size was selected according to G*Power software (effect size=0.75; test power=0.90; =0.05). Randomization was done by the researcher after obtaining participants' consent and participants were assigned to the intervention and control groups by a coin-throwing method. Inclusion criteria were: not being in the mastectomy and chemotherapy stage during training sessions, living in Ahvaz during the intervention, informed consent to attend the sessions of positive thinking training, taking no psychotropic medications at least three months before and during the study, minimum junior high school education, and having no severe neuropsychiatric disorders based on participants' self-reports. Exclusion criteria were: starting a simultaneous psychotherapy intervention and missing more than two treatment sessions during the intervention.

Before the positive thinking training, a pre-test was performed to assess perceived stress, metacognitive beliefs and death anxiety in women with breast cancer. The role of the pre-test in this study was to control and compare perceived stress, metacognitive beliefs and death anxiety in the intervention and control groups through the pre-test and post-test. The intervention group received eight 90-minute sessions (once a week) of positive thinking training. The post-test was then conducted on intervention and control groups to measure their perceived stress, metacognitive beliefs and death anxiety. At the end of the study, to observe ethical considerations, the control group received a course of positive skills training. Also, to take ethical considerations, the researchers received written consent from the participants for participation in the research. The study was approved by the Ethical Committee of Islamic Azad University, Bushehr Branch (code: 953001598).

Perceived Stress Scale: The Perceived Stress Scale (PSS) was developed by Cohen in 1983. The items were developed to elicit respondents' opinion about their uncontrollable, unpredictable, and difficult life. It is a 14-item inventory scored on a 5-point scale from 1=Never to 5=Always. Items 4, 5, 6, 7, 9, 10 and 13 were inversely scored. The minimum and maximum scores were 14 and 70. Badie et al., 25 reported the reliability of this scale equal to 0.86 based on Cronbach's alpha coefficient. In the present study, Cronbach's alpha coefficient was 0.82 for the scale.

Metacognitions Questionnaire (MCQ-30): The 30-item MCQ-30, developed by Wells in 2004, is a selfreport that measures individuals' beliefs. It was designed to measure several metacognitive elements, some of which play a pivotal role in the metacognitive model of psychological disorder. It consists of 5 subscales: 1) positive beliefs about worry, 2) negative beliefs about uncontrollability and danger of worry, 3) cognitive confidence in memory/attention, 4) beliefs about the need to control thoughts, and 5) cognitive self-consciousness. Cronbach's alpha coefficients for positive beliefs about worry, uncontrollability and danger of worry, cognitive confidence, the need to control thoughts, and cognitive self-consciousness were 0.77, 0.74, 0.84, 0.86 and 0.79, respectively. 26 In this study, Cronbach's alpha coefficients for positive beliefs about worry, uncontrollability and danger of worry, cognitive confidence, the need to control thoughts, and cognitive self-consciousness were 0.82, 0.85, 0.87, 0.84, and 0.83 respectively.

Scale of Death Anxiety: The Scale of Death Anxiety (SDA) was developed by Templer in 1970 to measure anxiety and fear of death. It is a 14-item inventory conducted with no time limits. The individuals are asked to answer 14 items with Yes or No and the scores range between 0 and 14. Higher scores indicate higher levels of anxiety and fear of death. Salmanian and Marashian, 27 reported the reliability of this scale equal to 0.88 based on Cronbach's alpha coefficient. In the present study, Cronbach's alpha coefficient was 0.86 for the scale.

The positive thinking training course was developed based on the power of positive thinking by Norman in 2010 and was provided to the intervention group in eight 90-minute sessions. 28 A summary of training sessions is provided in Table 1.

Data were analyzed by descriptive and inferential statistics: (mean, standard deviation, analysis of covariance (ANCOVA), and multivariate analysis of covariance (MANCOVA)). In addition, the ShapiroWilk test was performed to examine the normal distribution of the pre-test and post-test. Levene's test was performed to examine the equality of variances. SPSS version 22.0 was used to analyze the data.

The participants included 30 women with breast cancer, aged 42.81±7.35 years old. As shown in Table 2 In the present study, Shapiro-Wilk test was used before testing the normality of data distribution. According to the results of the Shapiro-Wilk test, the assumption of normality of scores in the intervention and control groups was met for perceived stress, metacognitive beliefs, and death anxiety. The assumption of normality of scores in the pre-test was met for both the intervention and control groups. Moreover, Levene's test was not significant for perceived stress, metacognitive beliefs, and death anxiety (P>0.05). By controlling the pre-test, all of the tests showed a significant difference between the intervention and control groups in terms of at least one of the variables of perceived stress, metacognitive beliefs, and death anxiety in women with breast cancer (F=124.69, P<0.001). One-way ANCOVA was used to find out which variable differed between the intervention and control groups.

As shown in Table 3, by controlling the pre-test, all of the tests indicated a significant difference between women with breast cancer in the intervention and control groups in terms of perceived stress (F=241. 23

The present study aimed to investigate the effecttiveness of positive thinking training on perceived stress, metacognitive beliefs, and death anxiety in women with breast cancer. Results suggested a significant difference between women with breast cancer in the intervention and control groups in terms of perceived stress, positive beliefs about worry, uncontrollability and danger of worry, cognitive confidence, the need to control thoughts, cognitive self-awareness, and death anxiety. In other words, given the mean scores of perceived stress, metacognitive beliefs and death anxiety, positive thinking training reduced these variables in women with breast cancer in the intervention group compared with the control group. This finding is consistent with the results of Shokrpour et al. 20 Women with breast cancer are not in good conditions due to perceived stress and cancer-induced death anxiety and they often experience high levels of worries which exacerbate their problems during the treatment process. 29 This study showed that positive thinking training reduces perceived stress and death anxiety in women with breast cancer. Positive thinking training in women with breast cancer provides useful strategies to identify negative thoughts on the disability to control stress and anxiety, and it helps these women know the stress they perceive, increase their coping ability and hardiness, and enhance their inner resistance to stress.

Positive thinking taught these women to have hope and think positively about their abilities, boosted their optimism, provided them with training techniques to identify negative and irrational thoughts, and helped them reduce stress, tension, and worry about diseaseinduced death anxiety. It assisted them in recognizing symptoms of stress and death anxiety, and increased their internal resistance to stress and stressful situations by mastering optimism and hope to moderate problems and stressors. These trainings can boost their hardiness, including stress management, mastering their condition, seeking challenges, thinking positively, and being purposeful in combating cancer-induced stress. 22 Isolation, stress-induced helplessness, and death anxiety decreased in these women. Positive thinking training helped them to recognize their positive experience in dealing with difficult and stressful situations caused by the suffering of the disease, strengthen their self-respect and self-esteem, develop well-being and resistance to tension, stress, and anxiety, boost their peace, and build hope. 20 Positive thinking training improved respect and self-esteem and cognitive resistance to negative stress in women with breast cancer. This training intervention strengthened positive thinking in women, facilitated their adaptation, regulated their emotions and positivism, and made them identify their positive traits. The development of these traits in women with breast cancer controlled their stress and tension caused by death anxiety that negatively affects their treatment process, and it reduced death anxiety. 30 Thus, they experienced less stress and anxiety and more peace of mind following positive thinking. In other words, positive thinking enabled the women with breast cancer to have an appropriate understanding of behaviors, attitudes, and feelings and to reduce stress by staying calm. Due to the creation of constructive and energizing thoughts through indoctrination, repetition and practice, these positive thoughts made the minds and thoughts of women with breast cancer positive. This positivism persisted in creating the right mood and controlled death anxiety in these women.

This study showed that positive thinking training reduced metacognitive beliefs in women with breast cancer. The ability to think positively in women with breast cancer helped them reduce negativism and rumination during the treatment process. In addition, positive thinking training improved their positive relations with others and their life and increased their happiness and success. Positive thinking training encouraged women to recognize their positive and good experiences and their role in increasing and enhancing self-respect and having a happy and joyful spirit. Following these effective techniques, the negative consequences of rumination for the disease were moderated. Negative metacognitive beliefs, which caused high concerns in these women, were controlled, and metacognitive beliefs decreased in them as positive waves were generated in their thoughts. Positive thinking made these women adopt an active position, shape their lives personally, and avoid negative thoughts as a strategy to alleviate the rumination-induced stress. 31 Positive thinking training solved psychological problems, reduced stress and anxiety, improved psychological well-being, hope and optimism for the future, and developed interpersonal skills, aesthetic feelings, perseverance and endurance, and spirituality in women with breast cancer, and it reduced metacognitive beliefs following optimism and hope. Positive thinking training also helped them identify resilience in the face of problems. They boldly reconstructed and repaired themselves in a behavioral and motivational manner. In addition, they showed fewer negative thoughts and metacognitive beliefs given their physical condition, because positive thinking boosted positive thoughts and hope in these women.

Positive thinking training creates a system of optimism in women, and builds hope in them; this approach is quite effective in reducing metacognitive beliefs over time. This study showed that positive thinking training reduces perceived stress, metacognitive beliefs and death anxiety in women with breast cancer. Counseling centers are recommended to apply positive thinking training and consider its effectiveness in reducing perceived stress, metacognitive beliefs, and death anxiety in women with breast cancer. Therapists are also recommended to apply positive thinking training in workshops to improve perceived stress, metacognitive beliefs, and death anxiety in women with breast cancer. In addition, health care providers are recommended to be attentive to the effect of positive thinking training on patient referral policies by identifying its effectiveeness in medical centers and prepare medical centers to use this protocol to alleviate cognitive problems and make optimal use of it for women with breast cancer.

Since the present study was performed on women with breast cancer visiting Shafa Health Center of Ahvaz city, caution should be observed in generalizing the results to other communities in different time and place situations due to different cultural conditions. Due to the difficulty of access to participants, it was not possible to conduct a followup stage to monitor the stability of the results. Another limitation was the small sample size in both groups. Considering these limitations and the paucity of studies on the effects of positive thinking training, there is a need for further studies to more precisely determine the effects of this integration.

This study was approved by the Ethical Committee of Islamic Azad University-Bushehr Branch (code: 953001598).