2.1. Effect of Music in Neuropsychiatric Conditions and PTSD
Various music and sound interventions have been used to improve health outcomes in a broad spectrum of psychological and neurological disorders
[35][36][37][38]. Music therapy has demonstrated significant effectiveness for the reduction of depression in people with dementia
[36][39] and improvement of mobility in people with stroke
[40]. Music therapy delivered by a professional music therapist revealed the efficiency of music to improve social interaction and communication skills in children with autism spectrum disorder
[41]. Moreover, there is evidence that music therapy in addition to standard care improved mental state and social functioning in schizophrenia patients
[36][42].
A meta-ethnography of 46 qualitative studies found that participatory music engagement, music actively made by the participant, including singing, and not limited by musical genre such as classical or jazz, improved well-being by facilitating self-development, providing respite from problems, and fostering social connections
[43]. There is growing evidence that music therapy can abate the stress response, decrease anxiety, and induce an overall relaxation response by reducing stress-inducing stimuli. A recent meta-analytic study by Witte et al. (2020) revealed the effectiveness of music interventions to relieve stress in a variety of settings, including mental health, polyclinic medical settings, medical surgery, and everyday life. The study’s findings demonstrated that pre-recorded relaxation music without lyrics could reduce physiological stress symptoms such as heart rate, blood pressure, and stress-related hormones, as well as psychological stress symptoms such as anxiety, nervousness, restlessness, and feelings of worry
[44]. McKinney & Honig (2017), examined effects from randomized and non-randomized controlled trials and found a medium to large effect of guided imagery and western classical music on various psychological measures including anxiety, and mood disturbance
[45]. Bradt et al. (2013) demonstrated the beneficial effect of patient-selected music from different styles of music such as jazz, easy listening, country and western, or classical music on preoperative anxiety and recommended its use as an alternative to sedative drugs
[46]. Hole et al. (2015) confirmed that Chinese classical music reduced postoperative pain, anxiety, and analgesia use and increased patient satisfaction
[47].
The effect of music and sound interventions has also been explored in ICU patients
[48]. Various forms of music interventions in ICU populations are found beneficial in reducing ICU-related anxiety and in-hospital stress
[48][49]. In mechanically ventilated patients, patient-directed music therapy is associated with lower anxiety scores, sedation frequency, and sedation intensity when compared to usual care
[50][51][52][53]. A majority of included studies used music that contains simple repetitive rhythms, low pitch, slow tempos, harmony and lack percussive instruments and vocals. Hetland et al. (2015) indicated that relaxing music, such as nature-based sounds, classical, and easy listening, can help manage pain, agitation, delirium, post-traumatic stress disorder (PTSD), anxiety, and depression in ICU patients by reducing the need for sedatives during mechanical ventilation, length of stay, and physiologic signs of anxiety and biomarkers of the stress response
[54]. Moreover, implementing music interventions in usual care is free of adverse side effects and can also reduce ICU costs. A recent study by Chlan et al. (2018) demonstrated that patient-directed music interventions can save about $2000/patient and concurrently better manage anxiety with less sedative medication than usual care
[55]. However, to date, the effect of music and sound interventions have not been explored in relation to the psychiatric disorders and PTSD after discharge from the ICU.
Despite this gap in evidence, music appears to be a promising adjunct in the treatment of PTSD
[35]. Evidence from various studies shows a significant effect of individual and group music therapy in the reduction of core PTSD symptoms and the increase in social function among PTSD patients. Creative art therapy also pointed out the potential of relaxation music therapy to creatively process, cope, and recover from PTSD
[56]. A mixed method study by Story and Beck (2017) reported experiencing classical music as a tool for coping with PTSD symptoms, particularly to regulate emotions, decrease arousal, express repressed feelings, and connect with others
[57]. Moreover, group music therapy in adult psychiatric patients with persistent PTSD, who had been unable to benefit from cognitive behavioral therapy CBT, showed a significant decrease of all dimensions of PTSD symptoms
[58]. The study explored therapist guided music improvisation technique using a variety of musical instruments such as xylophones, maracas, Indian bells, gato drums, djembe, tone bars, guitar, piano and cabassas.
Empirical evidence suggests that music therapy may reduce prominent symptoms of post-traumatic stress, including emotionally dysregulating intrusions, avoidance, negative alterations in mood, and arousal. A study by Zergani & Naderi (2016) demonstrated beneficial effects of Iranian traditional music on quality of life and anxiety symptoms among hospitalized veterans with PTSD
[59]. A double blinded randomized control trial, conducted by Pourmovahed et al., (2021) demonstrated that listening to non-verbal music can significantly reduce the severity of PTSD in mothers of premature infants hospitalized in NICU and promote emotional bonding between the mother and baby
[60]. The music included the sound of rain, sea, and nature with a slow, gentle, and soothing rhythm. Another randomized controlled trial that examined the effects of music therapy on symptoms of PTSD among prison inmates demonstrated a significant decrease in PTSD-symptoms
[61]. A mixed method study examining the efficacy of group drumming therapy in military veterans with PTSD indicated a significant reduction of specific symptoms such as isolation, lack of connectedness, avoidance of traumatic memories, rage, and anxiety
[62]. A mixed method study on the feasibility of group music therapy for women with PTSD and complex PTSD found significant changes in the PTSD, dissociation, anxiety, and depression scales, indicating symptom reduction
[63]. The qualitative analysis of participant experiences revealed that music assisted in establishing contact with feelings and bodily sensations, as well as providing an experience of expansion, relaxation, and new energy. Furthermore, six participants no longer had a PTSD diagnosis after treatment as shown by the PCL-5 cut-off values, which was sustained even at follow-up.
Music guided relaxation has also shown a positive impact in reducing depression, PTSD and increasing sleep quality in veterans
[35]. In a naturalistic study of 102 women with complex PTSD, guided imaginary and classical music significantly reduced symptoms of extreme stress, dissociation, interpersonal problems, and a sense of coherence
[64]. Another study demonstrated similar results of guided imaginary and classical music in refugees with PTSD. After sixteen GIM sessions, adult refugees showed positive improvements in PTSD symptoms, sleep quality, well-being, and social functioning
[65]. A recent randomized control trial with 74 refugees with PTSD, employing western classical music, New Age music, and music from the participants’ own national culture showed improvements in quality of life and fewer symptoms of psychological dissociation after music therapy
[66]. In addition, unlike the standard treatment, the positive effects of music and imagery were manifested even at the 6 month follow-up.
2.2. Mechanisms Underlying the Effects of Music in PTSD
Musical stimuli stimulate neural networks associated with various functional domains, such as movement, cognition, communication, emotion, and social responses
[67]. Studies clearly demonstrate that instrumental music without lyrics, Chinese and Western music can evoke changes in emotion and stimulate the brain structures involved with motivation, reward, and emotion
[68][69][70][71][72]. There is evidence that music can provoke changes in individual emotions, hormone arousal, emotional motor expression, and action movements
[69]. The studies included in this analysis used various experimental approaches, such as investigating music-evoked experiences of intense pleasure, emotional responses to consonant or dissonant music, happy or sad music, joy- or fear-evoking music, musical expectancy violations and music-evoked tension. Listening to joyful dance-tunes has been shown to reduce stress and enhance emotional responses, such as joy and peace
[72][73]. In particular, music is observed to stimulate increase in blood–oxygen level dependent (BOLD) signals in the amygdala, and the hippocampus
[72]. A meta-analysis of functional neuroimaging studies
[70] found that the amygdalae, hypothalamus, and hippocampus, which are vital parts of the brain in producing emotion and in experiencing PTSD symptoms, are stimulated by music. None of the included studies used music with lyrics. The ventral tegmental area (VTA), involved in dopamine production and release within the reward system, is also significantly activated by both unfamiliar musical pieces and the participant’s favorite music, in contrast, PFC activity was positively correlated with pleasure scores associated with music
[74][75]. However, favorite versus neutral music listening contrasts showed a greater activation in healthy participants than depressed patients
[74].
PTSD is characterized by hypervigilance associated with altered connectivity between the amygdalae and the hippocampus
[76]. Communication between these brain areas is vital in the symptomatology of PTSD. There is evidence that participant’s own favorite music to which they usually had a chill experience, can enhance the connection between the amygdalae, PFC, and the hippocampus
[77]. Moreover, contrast analysis of joy, fear and neutral musical stimuli revealed strongest BOLD signals in the superficial amygdala during joyful music, such as classical music, Irish jigs, jazz, reggae, South American and Balkan music
[78]. Thus, music could potentially play a role in balancing the processing of stimuli and in reducing the amygdala’s startle response so they can revert to the premorbid state. Moreover, attentive listening to musical clips played with the piano or violin can also stimulate PFC
[79], and therefore, can possibly recruit PFC to exert inhibitory control over amygdalic stress responses. Initiating communication between the amygdalae, PFC and hippocampus through music can, therefore, not only mitigate the hypervigilance of PTSD, but can also enhance cognitive processing of emotions.
Attentive listening to or playing music can stimulate neurogenesis and neuroplasticity in the brain
[67][73][80] which is relevant for individuals with PTSD who experience neuronal loss and impaired neurogenesis in parts of the limbic system. The increased hippocampal communication with the hypothalamus can also help balance the HPA axis
[80]. There is evidence suggesting that musical training in healthy participants can stimulate the hippocampus, induce neurogenesis, and produce a larger hippocampus
[81][82][83]. Altering the hippocampal volume can consequently increase positive emotions and regulate negative affect. Koelsch and Skouras (2014) reported increased functional connectivity between the hippocampus and hypothalamus, and amygdalae and nucleus accumbens during exposure to joyful music in healthy adults
[84]. The study used non-vocal joyful instrumental music from various epochs and styles. In addition, several studies on music-evoked emotions have reported activity changes in the hippocampus associated with a reduction of emotional stress associated with a lowering of the cortisol level
[73][85][86][87]. Overall, 75% of these studies involved experimenter-selected music (classical, new age or easy listening, and world), while the other 25% involved self-selected music, either “entirely self-selected” or “quasi-self-selected”. Clinical studies, which included a majority of the ICU population, demonstrated a stress-reducing effect of music listening irrespective of genre, self-selection of the music, or duration of listening
[85]. Classical music demonstrated a significant reduction in cortisol levels among mechanically ventilated ICU survivors
[86].
Evidence suggests that active vs. passive music therapy may have differential effects on patient engagement and receptivity. According to fMRI and PET scan studies, active music participation engages more parts of the brain than just listening to music
[88]. In a qualitative study, passive music therapy participants reported an immediate therapeutic effect, such as a reduction in anxiety
[89]. Active music therapy participants, on the other hand, described interactive session elements as stimulating, alleviating anxiety through pleasant social interaction. Music improvisation (drum based) has been found to be effective in expressing and managing emotions among veterans with PTSD
[62]. Moreover, a systematic review showed that passive listening to relaxing music didn’t seem to have any significant effects on PTSD symptoms, suggesting the importance of active music therapy to evoke change in PTSD patients
[56]. The researchers posited that specialist skills and an ongoing therapeutic relationship is vital in reducing symptoms of PTSD.
However, music selection needs careful consideration. Music that the participant does not enjoy may result in a stress rather than a relaxation response. Moreover, music can trigger strong memories, which influence the affective response to music and can, therefore, modulate the therapeutic effects of music
[90]. In the acute phase of critical illness, despite some controversy around the role of patients’ music preferences, it appears that patient-directed music selection associates with better outcomes
[91]. Several studies allowed participants to choose music from a variety of musical genres. However, participants’ choices were restricted within the range of selections offered by the researchers. Music interventions for mechanically ventilated patients reported participant dropout rates to be higher in researcher-selected music compared to patient-selected
[92]. Instead, studies involving a music therapist to assess patient music preferences have reported no dropouts and a high degree of participant satisfaction
[35][65][66]. Therefore, self-selected music appears to be associated with both the effectiveness of music interventions and participant retention.
Basic psychoacoustic properties of music, such as pitch (high or low tone of sounds), rate (fast or slow speed of sounds), loudness (loud or soft intensity of sounds), mode (major or minor key), timbre, and rhythm have been shown to be important factors in the perception and induction of positive as well as negative emotional states. The music therapy research supports music containing a slower tempo, low pitch, containing primarily string composition, regular rhythmic patterns, no extreme changes in dynamics, and no lyrics are associated with relaxation, joy, or peace
[93]. The tempo of 60–80 beats per minutes can help induce a state of relaxation and regulate emotions
[94]. A study by Beck et al., 2021, used predictable slow-tempo music to decrease arousal and induce relaxation in PTSD patients
[66]. In addition, the harmonic complexity of relaxing music should be consonant and remain within the diatonic key with a clear tonal center
[93][94]. Predictable music leads to positive responses, such as reward, appraisal, and pleasantness, thus it may support the relaxation response, while dissonant and unexpected harmonies with frequent chord changes activate the amygdala and defeat the purpose of emotion regulation
[95]. Research has stated that music with less sharp timbres has been proven to induce relaxation
[93]. Possible instrumental arrangements include piano, cello, flute and marimba
[94]. In addition, the use of instrumental music over nature sounds can effectively induce relaxation.