Functional role of frontal electroencephalogram alpha asymmetry in the resting state in patients with depression: A review

Table 1 The comparison of methods in studies on asymmetry pattern at resting state of clinically depressed individuals

Ref.	Sample		Age (yr)		% female	Diagnosis of depression	EEG detail
	Experimental group	Control group	Experimental group	Control group			Reference montage	EO/EC	Recording length (min)	Alpha range (Hz)
Henriques et al[20], 1991	EG: 15 depressed subjects	CG: 13 healthy controls	M = 40.40 (depressed subjects)	M = 40.61 (HCs)	60.7	SADS	CZ; AE; AR	E0+EC	1	8–13
Baehr et al[21], 1998	EG: 13 MDD	CG: 11 healthy controls	M = 43.50 (MDD)	M = 44.20 (HCs)		DSM-IV; BDI	Cz	EC	5	8–13
Beeney et al[22], 2014	EG: 13 MDD	CG: 21 healthy controls	M = 32.12 (MDD)	M = 27.78 (HCs)	100	DSM–IV; SCID	AL	E0+EC	8	8–13
Bruder et al[23], 1997	EG: 44 MDD (19 with and 25 without an anxiety disorder)	CG: 26 healthy controls	MDD with an anxiety disorder: M = 36.70; MDD without an anxiety disorder: M = 41.30	M = 32.90 (HCs)	50	DSM-III-R	NR	E0+EC	6	7.8–12.5
Cantisani et al[24], 2016	EG: 20 depressed subjects	CG: 19 healthy controls	M = 43.30 (depressed subjects)	M = 41.05 (HCs)	53.8	SCID; DSM-IV-TR	CA		6	8–12.5
Dharmadhikari et al[25], 2019	EG: 24 MDD	CG: 17 healthy controls	M = 34.82 (MDD)	M = 29.52 (HCs)	63.4	DSM-IV	auricle	EC	10	8--13
Gordon et al[26], 2010	EG: 92 MDD	CG: 1908 healthy controls			58.7	DSM-IV	AR	E0+EC	4	8–13
Gotlib[27], 1998	EG: 16 currently depressed, 31 previously depressed	CG: 30 never depressed				SCID	Cz	E0+EC	8	8–13
Jaworska et al[28], 2012	EG: 53 MDD	CG: 43 healthy controls				DSM-IV-TR; SCID-IV-I/P; HAMD; MADRS	AM; CZ; AR	E0+EC	6	8–13
Kemp et al[29], 2010	EG: 15 MDD	CG: 15 healthy controls	M = 39.90 (MDD)	M = 42.40 (HCs)	60	MINI; DASS	AM	EC	2	8–13
Koo et al[30], 2019	EG: 20 MDD	CG: 20 healthy controls	M = 51.05 (MDD)	M = 47.15 (HCs)		ICD-10/DSM IV	AE	EC	10	8–13
Roh et al[31], 2020	EG: 44 MDD without Suicidal ideation, 23 MDD with suicidal ideation	CG: 60 healthy controls	M = 39.30 (MDD); M = 37.48 (MDD with SI)	M = 34.83 (HCs)	85	DSM-IV	ECC	EO	3	8–12
Stewart et al[32], 2010	EG: 143 MDD	CG: 163 healthy controls	M = 19.10 (MDD)		69	DSM-IV	CSD; Cz; LM	E0+EC	8	8–13
Cai et al[34], 2020	EG: 24 MDD	CG: 22 healthy controls				DSM-IV; MINI	Cz	EC	5	8–14
Nusslock et al[35], 2018	EG: 37 depression, 18 anxiety + depression	CG: 69 healthy controls				SCID	AM	E0+EC	6	8–13
Brzezicka et al[36], 2017	EG: 26 MDD	CG: 26 healthy controls	M = 28.00 (MDD)	M = 24.90 (HCs)			CSD	EC	5	8–13
Jang et al[37], 2020	EG: 20 MDD, 18 patients with schizophrenia	CG: 16 healthy controls	M = 42.60 (MDD); M = 32.00 (MDD with schizophrenia)	M = 37.75 (HCs)	48.1	DSM-IV; MINI	BM	E0+EC	5	8–12
Segrave et al[38], 2011	EG: 16 MDD	CG: 18 healthy controls	M = 40.75 (MDD)	M = 42.11 (HCs)	100	DSM-IV	Cz; CA	E0+EC	6	8–13
Quinn et al[39], 2014	EG: 117 MDD	CG: 120 healthy controls				MINI; DSM-IV	AR; ER	EC	2	8–13
Smith et al[99], 2018	EG:143 lifetime MDD, 62 current MDD	CG: 163 healthy control			69	BDI; SCID	Cz	E0+EC	8	8–13
Vuga et al[40], 2006	EG: 49 childhood onset MDD	CG: 50 healthy controls	19-34	19-39	66.7	DSM-IV	Cz	E0+EC	6	7.5–12.5; alpha 1 (7.5–10.5); alpha 2 (10.5–12.5)
Gold et al[41], 2013	EG: 79 adults with depression		M= 35.60		78.5	DSM-III-R; SCID; MADRS	ALM	EC	5	8–12
McFarland et al[42], 2006	EG: 67 MDD		M = 34.64		65.7	SCID	LE	E0+EC	6	8–13
Kentgen et al[44], 2000	EG: 25 right-handed female outpatients	CG: 10 healthy controls			100	DSM-IV	NR	E0+EC	6	7.8--12.5
Feldmann et al[45], 2018	EG: 16 adolescents with depression	CG: 34 healthy controls	M = 16.08	M = 15.67	72.6	ICD-10; BDI	Cz; Mastoids; AE	E0+EC	8	7.5–13
Grünewald et al[46], 2018	EG: 20 adolescents (12–17 yr) with unipolar depression (12 with fifirst episode, 8 with recurrent depression)	CG: 31 healthy controls	M = 14.85 (unipolar depression)	M = 14.16 (HCs)	60.8	DSM-IV; ICD-10	AR		5	7.5–13.5
Deslandes et al[89], 2008	EG: 22 depressed subjects	CG: 14 healthy controls	M = 71.60 (depressed subjects)	M = 72.40 (HCs)	94	DSM-IV	ER	E0+EC	8	8–13
Kaiser et al[50], 2018	EG: 14 depression, 11 anxiety + depression	CG: 14 healthy controls	M = 78.60 (anxiety + depression); m = 80.50 (depression)	M = 80.90 (HCs)	100	GDS; HADS	RLMB	E0+EC	4	6.9–12.9
Carvalho et al[51], 2011	EG: 12 depressed subjects, 8 remitted subjects	CG: 7 non-depresse elderly subjects			66.7	DSM-IV	Earlobes	EC	8	8–12.9

EC: Eyes closed; EO: Eyes open; EEG: Electroencephalogram; HCs: Healthy controls; MDD: Major depressive disorder.

Diagnosis of depression: BDI: Beck Depression Inventory; DASS: Depression, Anxiety and Stress Scales; DSM-IIIR: Diagnostic and Statistical Manual of Mental Disorders, Third edition, Revised; DSM-IV: Diagnostic and Statistical Manual of Mental Disorders, Fourth edition; GDS: Geriatric depression scale; HAMD: Hamilton Rating Scale for Depression; HADS: Hospital anxiety and depression scale-depression; ICD-11: 11^th edition of the International Classification of Diseases; MADRS: Montgomery and Asberg Depression Rating Scale; MINI: Mini International Neuropsychiatric Interview; SADS: The Schedule for Affective Disorders and Schizophrenia; SCID: Structured Clinical Interview for DSM IIIR; SCID-IV-I/P: Structured Clinical Interview for DSM-IV, Axis I, Patient Version.

Reference montage: AE: The average across all 31 electrodes; AL: The average of all EEG leads; ALM: Averaged linked mastoids; AM: Averaged mastoids; AR: Average reference; BM: Both mastoids; CA: Common average montage; CA: Common average; CSD: Current source densities; ECC: The reference electrode was predefined; ER: Ear reference; LE: Linked ear; LM: Linked mastoids; NR: Nose reference; RLMB: The right and left mastoid bone.

Table 2 The comparison of methods in studies on asymmetry pattern at resting state of children inherited from generation to generation

Ref.	Sample		Age (yr)		% female	Diagnosis of depression	EEG detail
	Experimental group	Control group	Experimentalgroup	Control group			Reference montage	EO/EC	Recording length (min)	Alpha range (Hz)
Dawson et al[54], 1997	EG: 117 mothers and their 13-15-mo-old infants		13.74		44.4	DSM-IIIR; SCID; CES-D	ME		1	6–9
Diego et al[56], 2006	EG: 38 depressed	CG: 28 non-depressed	3-6 mo			CES-D	Cz			3–13
Field et al[57], 1995	EG: 17 depressed adolescent mothers	CG: 15 non-depressed mothers	3-6 mo		50	DISC; BDI	Cz		3	3–12
Jones et al[58], 1997	EG: 20 depressed group	CG: 24 non-depressed group	M = 18.00	M = 18.70		CES-D; SCID	Cz		3	2–6
Jones et al[59], 1998	EG: 35 mothers with depressive symptom	CG: 28 non-depressive symptom	M = 38.80	M = 39.50	48	CES-D	Cz		3	8.5–125
Tomarken et al[60], 2004	EG: 23 high risk	CG: 13 low risk	M = 13.10	M = 13.00	52.6	SCID	Cz	E0+EC	8	8.5–12.5
Lopez-Duran et al[61], 2012	EG: 90 high risk	CG: 45 low risk	M = 7.36	M = 7.93	46.6	DSM-IV; SCID	CA	E0+EC	3	7.5–11.5
Goodman et al[63], 2020	EG: 136 total infants.		M = 12 mo			DSM-IV	ARC		3	6–9
Wen et al[64], 2017	EG: 111 infants		6 mo of age (± 2 wk)			EPDS	Cz		2	6–9
Lusby et al[65], 2014	EG: 83 mother–infant dyads participated		3 mo and 6 mo only			DSM-IV	ARC		3	6–9
Dawson et al[69], 1992	EG: 31 infants		M = 14.21 (mo)		59.1	CES-D	Cz		1	6–9
Bruder et al[68], 2007	EG: 19 both parent and grandparent having MDD; 14 either parent or grandparent having MDD	CG: 16 neither having MDD	M = 15.40; M = 10.60	M = 13.60	53		LE	E0+EC	2	7–12.5

EC: Eyes closed; EO: Eyes open; EEG: Electroencephalogram; HCs: Healthy controls; MDD: Major depressive disorder.

Diagnosis of depression: BDI: Beck Depression Inventory; CES-D: Center for Epidemiological Studies-Depression Scale; DSM-IIIR: Diagnostic and Statistical Manual of Mental Disorders, Third edition, Revised; DSM-IⅤ: 4^th edition of the Diagnostic and Statistical Manual of Mental Disorder; EPDS: Edinburgh Postnatal Depression Scale; SCID: Structured Clinical Interview for DSM IIIR.

Reference montage: ARC: Average reference configuration; AS: Average signal; CA: Common average; Cz: The midline central position; LE: Linked ears reference; ME: Mastoid electrodes; NR: Nose reference.

Table 3 The comparison of methods in studies on frontal electroencephalogram alpha asymmetry of response to antidepressant treatment

Ref.	Sample		Age (yr)		Intervention time	% female	Diagnosis of depression	EEG detail
	Experimental group	Control group	Experimental group	Control group				Reference montage	EO/EC	Recording length (min)	Alpha range (Hz)
Arns et al[70], 2016	EG: 236 Escitalopram, 251 Sertraline, 235 Venlafaxine-XR	CG: 336 controls	M = 38.85 (Escitalopram), M = 38.34 (Sertraline), M = 38.46 (Venlafaxine-XR), M = 37.84 (MDD)	M = 36.99 (Controls)	8 wk	57.03	DSM–IV; MINI; HRSD	AM	E0+EC	2	8–13
Vinne et al[71], 2019	EG: 136 treatment with escitalo pram, 169 treatment with sertraline, 188 treatment with venlafaxine-extended release				8 wk	54.47	MINI; HRSD; VQIDS-SR	AM	E0+EC	4	8–13
Bares et al[72], 2019	EG: 57 SSRIs, 46 SNRIs		M = 46.04 (SSRIs), M = 44.83 (SNRIs)		1 wk	74.76	DSM IV; MADRS; CGI	Cz	EC	10	8–13
Szumska et al[73], 2021	EG: 12 Mindfulness group	CG: 8 control group	M = 32.40 (Mindfulness group)	M = 35.00 (Control group)	8 wk	55	CES-D; MINI	Cz	E0+EC	3	8–13
Keune et al[74], 2011	EG: 78 MDD; 40 MBCT group	CG: 37 a wait-list condition	M = 48.93 (MBCT group)	M = 45.24 (wait-list group)	8 wk	74.03	DSM-IV	AM	E0+EC	8	8--13
Barnhofer et al[75], 2007	EG: 10 MBCT	CG: 12 treatment-as-usual	M = 48.00 (MBCT)	M = 38.60 (treatment-as-usual)	8 wk	50	MINI	AE	E0+EC	8	8–13
Gollan et al[77], 2014	EG: 37 MDD; Behavioral activation	CG: 35 non-MDD			16 wk	62.50	DSM-IV; IDS-C	AM	E0+EC	8	8–13
Allen et al[14], 2004	EG: 30 nonpharmacological intervention				8 wk	100	DSM–IV; HRSD	Cz; AM, AR	E0+EC	8	8–13
Spronk et al[78], 2008	EG: 8 MDD; rTMS Treatment		M = 42.60 (rTMS Treatment)			37.50	BDI; SCI	AM	E0+EC	2	alpha 1 (8–11); alpha 2 (11–13)
Wang et al[80], 2016	EG: 7 neurofeedback group		M = 47.43		6 wk	78.57	DSM-IV	Cz	EC	5	8–12
Vlcek et al[79], 2020	EG: 9 LF rTMS responder	CG: 16 LF rTMS non-responders			4 wk	80	MINI; MADRS; CGI	Cz	EC	10	8–12; 8–10; 10–12

EC: Eyes closed; EO: Eyes open; EEG: Electroencephalogram; HCs: Healthy controls; LF rTMS: Low-frequency Rtms; MBCT: Mindfulness-Based Cognitive Therapy; MDD: Major depressive disorder; rTMS: Repeated transcranial magnetic stimulation; SNRIs: Serotonin norepinephrine reuptake inhibitors; SSRIs: Selective serotonin reuptake inhibitors.

Diagnosis of depression: BDI: Beck Depression Inventory; CES-D: Centre for Epidemiological Studies Depression scale; CGI: Clinical Global Impression; HRSD: Hamilton rating scale for depression; MADRS: Montgomery and Asberg Depression Rating Scale; IDS-C: Inventory of Depressive Symptomatology–Clinician-Rated; MINI: Mini International Neuropsychiatric Interview; SCI: Structural clinical interview; VQIDS-SR: Very Quick Inventory of Depressive Symptomatology–Self Report.

Reference montage: AM: Averaged mastoids; AR: Average reference; Cz: The midline central position.