Portable electroencephalography in early detection of depression: Progress and future directions

Table 2 Categories of portable electroencephalography

Type	Technical characteristics	Advantages	Limitations	Ref.
Head-worn EEG	Dry/wet electrodes, rigid/semi-flexible headset, 4-16 channels	Detects depression-related EEG biomarkers in key prefrontal regions, suitable for lab or remote screening	Limited comfort, prone to motion artifacts	[17-19,23,24,26,39]
Ear-worn EEG	Sensors in earplugs or ear-mounted devices, dry electrodes, 1-2 channels	All-day wearability, suitable for daily emotional monitoring, supports auditory stimulus experiments	Limited signal coverage, susceptible to EMG noise	[55-57]
Textile-integrated EEG	Sensors embedded in wearable textiles (e.g., smart caps, headbands), conductive materials	Suitable for long-term monitoring, natural user experience, home or clinical use	Lower signal quality than standard EEG, affected by textile movement	[20,58]
Implantable EEG	High-precision EEG acquisition, ultra-thin flexible electrodes for skin adhesion	Precise monitoring for severe depression, can be combined with tDCS for therapy, high-quality data	Highly invasive, limited to specific medical contexts, patch requires frequent replacement	[59]

EEG: Electroencephalography; EMG: Electromyogram; tDCS: Transcranial direct current stimulation.