2.4.1. Sleep, Performance Enhancement, and Cognitive Health

The combination of EEG and HRV biofeedback has proven effective in enhancing sleep, supporting cognitive health and boosting performance across different settings. For instance, Lee et al. developed a sleep monitoring system integrating EEG, ECG and accelerometer data to encourage deeper sleep and smoother wakefulness by aligning users’ circadian rhythms through neurofeedback. This approach led to improvements in sleep depth and quality . Meanwhile, Meeuwsen et al. found that a program combining z-score neurofeedback, HRV biofeedback and memory coaching could improve both cognitive function and emotional well-being in older adults with memory concerns, suggesting the value of biofeedback in reducing age-related cognitive decline . In high-stress training settings, Stikic et al. highlighted that EEG-based neurofeedback, coupled with HRV metrics, helps users adapt to demanding environments by providing feedback on cognitive load and engagement levels—an approach particularly useful in areas like military training or competitive sports .

For mental health and emotional balance, especially in conditions like PTSD, depression and autism, EEG and HRV biofeedback also appear beneficial. Wahbeh and Oken showed that combining HRV biofeedback with EEG markers can stabilize emotional responses in PTSD patients by modulating autonomic balance, a key factor in emotional resilience . Bell’s study on PTSD reinforced this, finding that pairing LORETA z-score neurofeedback with HRV biofeedback helped target specific brainwave abnormalities associated with PTSD, which reduced symptoms significantly . Likewise, Melnikov reviewed HRV and EEG biofeedback as promising, if still emerging, tools for depression management, and Fernández-Alvarez et al. supported this in a meta-analysis showing biofeedback’s complementary role in reducing depressive symptoms , . Extending biofeedback’s reach into autism therapy, Goodman et al. demonstrated that HRV biofeedback, alone or paired with neurofeedback, could enhance emotion regulation and reduce behavioral symptoms in children with ASD, which underscores its potential for neurodevelopmental conditions . Moreover, Friedrich et al. designed a game-based neurofeedback system specifically for children with autism spectrum disorder (ASD), combining EEG and heart rate feedback to enhance emotional regulation and social engagement . Michael and Kaur’s review on depression examined how HRV metrics could aid in personalizing repetitive transcranial magnetic stimulation (rTMS) treatments, presenting a new application for EEG and ECG data in mental health therapy by focusing on the autonomic nervous system . Lastly, Michałowski et al. examined the neural and cardiac responses of individuals with specific phobias, helping to open the way for interventions that could mitigate fear responses by drawing on users’ unique brain-heart response patterns . Altogether, these studies suggest EEG and HRV biofeedback may become valuable tools for a range of psychological needs.