Binaural Beats’ Effect on Brain Activity and Psychiatric Disorders: A Literature Review

3.1. Binaural Beats and Memory

Memory functions are linked to fluctuations in brain electrical activity, specifically in theta, alpha, and gamma frequencies, which can impact different aspects of memory [10]. Generally, when binaural beats are stimulated for 5-30 minutes, they attract brain waves to the frequency of the beats. The most potent behavioral and psychological effects of binaural beats are observed at frequencies around 400 Hz, with a maximum difference of 35 Hz [11].

High frequencies of binaural beats, like beta and gamma, can help improve memory and concentration, respectively, which can be related to various brain states in these frequencies, such as deep sleep (delta) or fatigue (theta). Binaural beats have been found to enhance working memory, an essential function of the central nervous system that temporarily stores information during cognitive activities, such as reading, comprehension, and learning [11-14]. Neuromodulation research has focused on the potential of working memory to improve cognitive and behavioral outcomes. Improving working memory through the use of binaural beats can help in the transfer of information from active memory to long-term memory, ultimately leading to better long-term storage and retrieval [2, 15, 16]. Research has shown that the effect of binaural beats on long-term memory can vary depending on the frequency used. In general, the beta frequency is more effective in enhancing long-term memory compared to the theta frequency. Also, in binaural beats with alpha frequency, studies have shown that it can improve memory in disabled children and the elderly who naturally experience a decrease in alpha activity [16, 17].

Several studies contradict the previously mentioned results. For example, Beauchene conducted a study that found no effect on verbal memory after 5 minutes of binaural beats stimulation with alpha frequency [18]. Similarly, Wahbeh's 2007 study reported opposite results with theta frequency. In this study, stimulation with binaural pulses at 7 Hz for a 3-minute session decreased verbal memory, while at 5 Hz for 15 minutes twice a day, it increased the verbal memory [19]. Also, the literature has revealed significant variability in results, with some studies reporting no significant changes in memory task performance when comparing binaural beats to control conditions [10]. The discrepancies in findings on the effects of binaural beats can be attributed to variations in study designs, exposure frequencies, and durations. Additionally, some studies have analyzed the impact of binaural beats both during and after exposure, contri- buting to further disparities in results. Nevertheless, ongoing research seeks to establish more definitive conclusions regarding the influence of binaural beats on memory.

In summary, while there is evidence suggesting that binaural beats may enhance certain aspects of memory, particularly with specific frequencies, like beta, contra- dictory findings highlight the complexity of their effects. Further research is essential to reconcile these differences and establish clearer guidelines regarding the use of binaural beats for cognitive enhancement.

3.2. Binaural Beats and Cognition

The mental action or process of learning through experience, thought, and the senses is known as cognition. It includes all facets of cognitive abilities, including perception, attention, thought, imagination, intelligence, knowledge formation, memory and working memory, judgment and evaluation, reasoning and computation, problem-solving and decision-making, comprehension, and language production. Cognitive processes rely on as well as generate new knowledge [20, 21].

Various studies have investigated the effect of binaural beats on cognition. The study by Sharp et al. showed that binaural beats at 40 Hz significantly improved cognition, while at 25 and 100 Hz, the amount of improvement was less [22]. Evidence shows that gamma-frequency binaural beats can enhance cognitive flexibility and improve divergent thinking [23]. However, according to previous studies, gamma frequency binaural beats’ effect on cognitive performance relies on personal differences [24]. Beta-frequency binaural beats are known as a means of enhancing cognitive control in adults. This finding was obtained in an interventional study and from the results of behavioral analysis and various Event-related Potentials (ERP) of the participants [20].

Conversely, research indicates that binaural beats may have no significant effect or even detrimental effects on cognition. A study involving 1,000 participants found that listening to binaural beats during cognitive tasks led to decreased performance scores, suggesting that rather than enhancing cognitive abilities, these auditory stimuli might impair them [25]. This aligns with findings from systematic reviews that highlight the inconsistency in results across various studies, where some report positive outcomes while others show no effect or negative impacts on cognitive performance [1, 5].

In summary, while some evidence supports the cognitive enhancement potential of binaural beats, significant research indicates that they may not be universally beneficial and could even impair cognitive function under certain conditions. Further investigation is necessary to clarify these effects and establish reliable guidelines for their use.

3.3. Binaural Beats and Major Depressive Disorder

Major Depressive Disorder (MDD) was predicted to take the top rank by 2030 by the WHO, which placed it as the third most common cause of disease burden globally in 2008 [26]. When someone has suicidal thoughts or a persistently low or depressed mood, anhedonia, which is a loss of interest in pleasurable activities, guilt or worth- lessness, a lack of energy, poor concentration, changes in appetite, psychomotor retardation or agitation, sleep disturbances, or any of these symptoms, medical attention should focus on them [27].

In a randomized controlled trial study on patients with mild to moderate acute phase of depression, it was found that listening to binaural beats with an alpha frequency of 10 Hz for 30 minutes every day for 5 days significantly reduced depression scores. Binaural beats can cause changes in the electrical activity of the brain cortex. By increasing alpha power in the occipital region and increasing gamma in the prefrontal region, they can have therapeutic effects on cortical activity and depression improvement [28]. In the study by Vetkar et al., it was found that the use of binaural beats combined with art therapy was beneficial in the improvement of fatigue and depression symptoms [29]. There are not many studies on the effect of binaural beats on depression, but those present vary in their conclusions. For instance, a study by Daengruan et al. found that MDD patients who received 10 Hz binaural beats in addition to standard treatment showed no significant difference in their depression scores from the control group [30]. Conversely, some studies have reported that binaural beats can exacerbate feelings of depression. For instance, some participants experienced heightened feelings of depression after listening to theta-frequency binaural beats [1]. This highlights the variability in individual responses to binaural beat therapy. A randomized controlled trial specifically examining the use of 10 Hz binaural beat music in conjunction with standard treatment for MDD found no significant differences in outcomes compared to standard care alone [30].

The current body of research presents a mixed picture regarding the efficacy of binaural beats for treating major depressive disorder. While some findings support their use as a potential adjunctive therapy for improving mood and reducing depressive symptoms, there are also significant concerns about their effectiveness and the possibility of adverse effects.

3.4. Binaural Beats and Anxiety

A class of extremely common mental health issues known as anxiety disorders can have a crippling effect on everyday functioning and general well-being. They may co-exist with different mental health conditions, such as depression [31].

A meta-analysis of 22 studies evaluating the effective- ness of binaural beats concluded that binaural beats can be effective for one’s anxiety, attention, memory, and perceived pain, considering different factors, such as the moment of exposure (since the binaural beats are more effective if they are presented before or during the procedure), frequency of the beat (complex-frequency binaural beats have the largest effect), what it is masked with (binaural beats are more effective when they are not masked with music, but there is no difference if they are masked with white or pink noise), and duration (time under exposure does not cause habituation and it should be long enough for obtaining the benefit) [13]. Binaural beats can even be used to reduce anxiety in certain situations (such as preoperative). It has been shown in a study that binaural beats and 432 Hz music can both be effective in reducing preoperative anxiety [32]. It has also been shown in a study that binaural beats can reduce anxiety and pain while undergoing either diagnostic cystoscopy or urethral stent removal [33]. Several studies have shown the effectiveness of binaural beats listening in reducing anxiety levels and have also proven binaural beats to be more effective than monaural beats in reducing anxiety [34, 35]. An important point is that according to the evidence, binaural beats can exert their effectiveness in the context of a healthy nervous system, and if the nervous system is defective, the effectiveness of binaural beats is debatable [36]. Some recent studies have found no significant impact of binaural beats on anxiety levels. For instance, a 2023 study specifically examining gamma frequency binaural beats reported no differences in self-rated anxiety measures before and after exposure [37]. This aligns with findings from a systematic review that have resulted from the synthesis of various studies; it has been revealed that while some have supported the brainwave entrainment hypothesis, many others have reported inconsistent or null results regarding anxiety reduction [5].

3.5. Binaural Beats and Sleep Disorders

Sleep is crucial for one's health and well-being. Sleep disruption lowers life quality and sleep quality, increases the risk of secondary diseases, and may be brought on by other medical conditions [38].

According to a preliminary study, binaural beats may improve sleep quality. In a study, binaural beats with a 3 Hz delta frequency were used to produce delta activity in the brain. Binaural beats lengthened stage three sleep as a result. For feeling fresh in the morning, stage three sleep must be deep [39]. The potential benefits of binaural beats in promoting improved sleep have been shown by other small research studies. In a study, soccer players who listened to binaural beats between 2 and 8 Hz reported better sleep quality, reduced sleepiness, and easier waking up [40]. Additionally, binaural beats may help in lowering anxiety, in turn promoting better sleep [13]. A study by Dabiri et al. showed using a 3 Hz binaural beat on a 174 Hz carrier tone for 90 minutes before going to bed while lying down with closed eyes to have positive effects on one’s mood and sleep quality [41]. In a study investigating the binaural beats' effect on sleep in patients with mild insomnia and using EEG, it was concluded that listening to music with the binaural beat (a 6 Hz binaural beat) resulted in an increase in theta wave, being associated with sleepiness [42]. Based on a study by Dini et al., binaural beats significantly improved the overall score for both insomnia and poor sleep quality [43]. However, contradictory findings also exist. One study found that binaural beats could negatively affect cognitive performance and suggested that prolonged listening to binaural beats, regardless of frequency, can be bother- some [25]. A review concluded that most studies on binaural beats are limited or contradictory, and there is evidence of diminishing impact over time, with more research needed to understand their potential benefits fully.

3.6. Binaural Beats and Brain Electrical Activity

The electrical activity of neurons in the brain produces a small voltage signal on the surface of the skin, known as Electroencephalographic (EEG) signals or electrical brain waves. There are four dominant frequency bands of brain waves, each related to distinct brain functions. Beta waves are associated with thinking, concentration, and infor- mation processing. Theta waves are linked to memory and dreaming, while alpha waves are linked to a state of alertness and calmness. Delta waves are associated with deep sleep [44].

The binaural beats alter the brain's excitability and can be measured with EEG. Listening to binaural beats with a frequency of 10 Hz can increase delta brain waves in both hemispheres. Since delta waves are linked to deep sleep, it can be concluded that binaural beats have similar effects as meditation, even though people are awake during testing and it is difficult to accurately measure the delta wave that is dominant in deep sleep. Stimulating the brain with binaural beats of alpha frequency increases theta waves in both hemispheres, suggesting that binaural beats can improve memory and help induce the dreaming state [44, 45].

Moreover, the use of binaural beats at alpha frequency resulted in an increase in alpha brain waves, which was particularly evident in the frontal and central regions of the brain. Given that alpha waves contribute to main- taining a state of relaxation while also enhancing alertness, it is reasonable to assert that binaural beats are effective in boosting these states [46-49]. Previous studies have demonstrated that exposing individuals to binaural beats with three different frequencies (delta, alpha, and beta) can lead to an increase in beta brain waves, particularly in the left hemisphere. Since beta waves are known to positively impact brain function, this increase can lead to improvements in concentration, information processing, and critical thinking abilities [50].

Some studies have shown different results than those previously mentioned. Kim et al. conducted a study that found binaural beats with delta, beta, alpha, and theta frequencies to decrease delta and theta waves, while increasing alpha and beta waves [51]. Additionally, Norhazman conducted a study in 2015 that showed that binaural beats with a 9 Hz frequency increased alpha waves, but decreased beta waves [48]. Goa et al. reported that listening to binaural beats with beta frequency reduced brain theta waves [36].

Therefore, the way that the binaural beat is presented, including its frequency and duration, as well as the specific locations in the brain where changes occur, can greatly influence the excitability of the cerebral cortex and the resulting modulation effect [52, 53].

A study by López-Caballero concluded that binaural beat stimulation did not enhance Electroencephalographic (EEG) power or emotional arousal. The researchers found no significant changes in EEG spectral power or psycho- physiological measures, like heart rate and skin conductance, across various beat frequencies tested [54]. A systematic review encompassing 14 studies highlighted inconsistencies in the effects of binaural beats on brainwave entrainment. While five studies supported the hypothesis that binaural beats can synchronize brain oscillations, eight studies reported contradictory results, and one yielded mixed outcomes. This variability was attributed to methodological differences among the studies, including variations in experimental design and EEG parameters [5].