Postpartum blues refers to mood swings experienced in the first days after childbirth [1]. It usually begin three to four days after childbirth with maximum symptoms in the first five days, which often subside by the tenth day [2]. Symptoms include persistent crying, emotional instability, fatigue, temporary anxiety and confusion, sleep and appetite disorders, anxiety, and irritability [1]. The prevalence of postpartum blues varies from 30% to 85% in different countries [3,4]. It is usually a self-limiting condition which improves with social and family support (and without medication). However, if it lasts more than two weeks, more severe mental disorders, especially postpartum depression, can occur among 20% of individuals with postpartum blues [4]. Postpartum depression, the second most common psychological problem in the postpartum period, occurs often within the first three months after childbirth [5]. Postpartum depression includes depressed mood, sleep and appetite disorders, low energy, anxiety, suicidal ideation, feelings of guilt and inadequacy in caring for the baby, and not paying attention to the well-being and safety of the baby [6].

Mothers with postpartum blues, postpartum depression or other mental health illness experiences can have trouble in caring for their child and can have attachment insecurity regarding their children [7]. Consequently, postpartum blues can become a psychological problem (e.g. postnatal depression) if ignored [8]. While postpartum blues does not have any specific medical treatment, it should be monitored in relation to the occurrence of the diagnostic criteria of postpartum depression [9]. The administering of antidepressants is the conventional medical treatment for postnatal depression, although there is the important concern regarding transition of metabolites to the mother's milk during breastfeeding [10]. Some mothers do not accept conventional medical interventions due to their maternal side-effects (e.g. dry mouth, palpitations, and possibility of excretion to their milk) while breastfeeding their infants [11]. Therefore, complementary therapies with no chance of chemical secretion in mothers' milk, are more acceptable therapeutic options for this group of women [12]. There are several ways to reduce postnatal mood disorders and postpartum depression, including counseling, self-care, relaxation, music therapy, herbal medicine, acupuncture, and acupressure [2,4].

Auricular acupressure, one form of complementary and alternative medicine, uses the ear as a target point of acupressure [13]. As one of the body's microsystems, the ear has connection to different body organs and their functions, and can be used to diagnose, treat, and prevent diseases [14]. The stimulation of acupoints increases natural biochemicals for pain relief in serum and cerebrospinal fluid neurotransmitters such as enkephalins and monoamines [15]. Therefore, acupressure slowly restores the body to a harmonious state and helps to treat disease and health-related problems [16]. Also, by stimulating the ear points using acupressure, the benefits can be enjoyed for days and even weeks [17].

The promising effect of auricular acupressure on depression has been studied in different target groups including outpatient nurses [18], patients with post-stroke depression [19], older adults in long-term care institution [[20], [21]], nursing students experiencing sleep disturbances [22], and breast cancer patients [23]. In an integrative review, Hmwe et al. reported evidence from 19 studies that acupressure can be beneficial for older people who suffer from depression [24].

Very few studies have been conducted on the effects of auricular acupressure on postpartum depression. A 2018 review and meta-analysis reported that three clinical trials compared the effects of acupuncture with fluoxetine and found the effect of acupuncture can be the same as fluoxetine in improving postpartum depression [25]. Kuo et al. [17] reported significantly lower anxiety, fatigue, and cortisol levels after auricular acupressure. Also, Kim et al. reported a positive effect of auricular acupressure in decreasing depression and fatigue among early postpartum mothers [26]. However, Mousavi et al. [27] found no effect for auriculotherapy on anxiety after cesarean section. One of the weaknesses of Mousavi et al.‘s study was the short-term follow-up after cesarean section (just 2 h later). To the best of the present authors' knowledge, the effect of auricular acupressure on postpartum blues has not been previously investigated. Postpartum blues is a preliminary situation which can be worsen if ignored and may lead to postpartum depression. Trying to eliminate postpartum blues in a timely way may prevent the onset of postpartum depression. Therefore, the present study investigated the effect of auricular acupressure on the severity of postpartum blues.