Despite considerable advances in medicine, cancer is still one of the most serious diseases of our era and the third leading cause of death, accounting for about 12% of mortalities worldwide (
1). According to statistics released by the World Health Organization (WHO), about 70% of all cancer-related deaths occur in developing countries (
2). Breast cancer is one of the most common types of cancer among women that accounts for nearly one-fifth of deaths in women aged 40 to 50 years (
3). According to the Statistics Management Center of the Iranian Ministry of Health, breast cancer still ranks the first among all cancers in Iranian women (
4).
Cancer patients receive physical therapies such as surgery, chemotherapy, and radiotherapy, but less attention is paid to their mental health. Breast cancer is the most psychologically serious cancer among women (
5). Patients with this type of cancer have high levels of mental disorders ranging from depression, anxiety, and incompatibility with illness to anxiety disorders and death (
6). Studies have shown that the incidence of cancer is associated with increased mental disorders such as depression, anxiety, and decreased quality of life (QoL) in patients (
5).
Women with breast cancer who undergo surgery usually lose an organ that is a symbol of their gender, and this can negatively affect the woman’s mental image of her body, further leading to a decrease in her self-confidence and attractiveness, followed by anxiety, depression, and despair (
4). Cancer patients experience varying degrees of depression, anxiety, and hopelessness. In addition, it is important to note that people with chronic and incurable physical illnesses are less happy (
7). A study by Albertson et al. (
8) on happiness in people with breast cancer also showed that decreased happiness was associated with increased pain and anxiety in these patients.
Happiness is usually defined as the feeling of joy and inner satisfaction of one’s life and is used as an umbrella term that covers the concepts related to a good life, which is now referred to as QoL and life satisfaction (
9). Happiness is generally considered as a predictor of health status and longevity (
5). Wnuk et al. (
10) showed that patients with breast cancer who had a purpose in life had higher happiness.
Previous studies reported that not only the physical health of patients but also their mental health should be considered in the treatment process. This being so, psychological studies have taken different approaches to patient mental health. Karamozan et al. (
11) showed that stress management is associated with improved self-efficacy and increased happiness in patients with breast cancer. However, some studies have found that the sadness and frustration of these patients are related to the purpose of life (
12,
13).
Hope therapy is one of the cognitive therapies that follow an approach to positive psychology. It focuses on human capabilities and strengths, rather than weaknesses. Hope is positively correlated with self-worth and negatively associated with depression, anxiety, and sadness. Snyder, the founder of hope theory and hope therapy, considers hope as a process that individuals set goals, develop specific strategies by which to achieve those goals, and build and sustain the motivation to execute those strategies. According to Snyder, hope is not a passive emotional phenomenon that occurs only in the darkest moments of life (
14,
15). Hope-based therapies have been shown to affect hope and health (
16), the happiness of hemodialysis patients (
17) and the elderly (
18), and the self-efficacy of physically disabled men (
19).
The incidence of breast cancer is on the rise and, according to the statistics released by the WHO, cancer deaths were expected to increase to more than 15 million people per year by 2020 (
2). Women with breast cancer experience various aspects of mental health problems. Therefore, it seems that the biggest problem of these patients is sadness and despair (
20), which results from the lack of meaning in life.