With a lifetime prevalence of up to 6.1% worldwide, posttraumatic stress disorder (PTSD) is a major public health problem [
1]. PTSD often results from substantial traumatic experiences and is thus far more common among veterans, survivors of wars or natural disasters, and victims of violence. The syndrome is associated with re-experiencing, avoidance, arousal, cognition, and mood symptoms [
2].
A wide range of pharmacological and psychotherapeutic approaches are used in the treatment of PTSD [
3]. Recent meta-analyses demonstrated that differences between most pharmacological treatments for PTSD and placebo are small at best [
4,
5]. While phenelzine seems to be most effective, the paucity of available studies hindered definite conclusions [
5]. The strong placebo effect in pharmacological treatment of PTSD might be a main reason for their perceived efficacy [
4]. Psychotherapy, especially trauma-focused psychotherapy, seems to be superior to medication as a first-line treatment [
6]. While psychotherapy thus seems to be the most promising first-line treatment for PTSD [
3], a recent Cochrane Review rated the quality of evidence to be very low even for trauma-focused psychotherapy; and a considerable number of patients terminated the included psychotherapeutic trials early during the treatment period [
7]. The latter might hint to a limited tolerability of these treatment approaches in some patients. In recent years, complementary therapy approaches for individuals with PTSD and other trauma-related disorders have received increasing interest [
8]. Specifically mind-body approaches might be able to decrease trauma-related symptoms and emotion dysregulation [
9]; and could thus be offered when patients are not able to tolerate psychotherapeutic treatment.
The most commonly used mind-body approach is yoga, a traditional Indian philosophical and spiritual school, as well as a health care practice which originated more than 3000 year ago and combines physical activity, mindfulness, relaxation, and breathing exercises [
10]. Beside physical aspects, traditional yoga comprises ethical and spiritual perspectives. Modern yoga forms mostly comprise physical poses, breathing exercises, and meditation. Therefore, yoga is a holistic approach, which is thought to help uniting body, mind and spirit [
10]. Thus, yoga is increasingly used to foster physical and mental well-being [
10]. The efficacy of yoga in improving comorbid mental symptoms could be shown for different health conditions such as pain [
11] and cancer [
12]. There also is emerging evidence of efficacy of yoga as an ancillary treatment for psychiatric conditions such as depression [
13‐
15], anxiety disorders [
16,
17], and perhaps psychosis [
18‐
20]. Yoga has become one of the most commonly used complementary therapy approaches in Northern America [
21]. With respect to potential mechanisms of action, physical activity is a major element in yoga and this physical activity alone already seems to improve PTSD symptoms [
22]. It has however been argued that by reducing stress-induced allostatic load and increasing parasympathic activity, yoga can directly reduce amygdala hyperactivation and elevated cortisol levels in patients with PTSD and thereby reduce symptoms [
23]. This shift in autonomic balance to the parasympathic branch of the autonomic nervous system seems to be mainly triggered by breathing, relaxation, and meditation which are specific to yoga interventions [
24]. Beyond biological mechanisms, yoga might potentially impact PTSD via different psychological pathways. Two major mechanisms of the paradox that patients feel anxious about the future although the traumatic event lies in the past were identified: negative appraisals of the trauma or its sequelae and the nature of the trauma memory itself [
25]. Negative appraisals include overgeneralization, negative appraisal of own actions, negative reactions by other people and life prospects. These different types of appraisals can trigger the different emotional experiences by patients with PTSD [
25]. Yoga often involves aspects of mindfulness, ie, a non-judgmental mindful attention to and acknowledgment of even unpleasant emotions or memories [
26]. This is thought to increase emotion regulation rather than avoidance. The mindful awareness of the transitory nature of one’s momentary physical, sensory, and emotional experience during yoga practice is thought to lead to a change in self-appraisal [
27] and to also induce positive effects on PTSD symptoms [
28]. Furthermore, even unspecific relaxation has been shown to contribute to an amelioration of PTSD symptoms although to a much smaller extent than more specific psychotherapeutic approaches [
29]. Physical activity in yoga is mainly associated with an increased attentional focus to bodily perceptions and sensations. This can increase body awareness and potentially accurate identification of the triggered emotional response [
30]. Beyond that, the social support in yoga classes might positively influence negative cognitive appraisals [
31].
This systematic review aimed to investigate and meta-analyze the evidence of yoga for symptoms of PTSD.