Table 1.

Summary of candidate gene studies on adult attachment

Gene	Marker	Ref.	Adult attachment measure	Result
OXTR	rs53576	Costa et al[39], 2009	ASQ	GG greater insecurity
		Monin et al[39], 2019	ECR	GG lower anxiety and avoidance
		Raby et al[44], 2013	CRI	GG predicts continuity of attachment security
		Fraley et al[11], 2013	RSQ	No significant associations or interactions with maternal sensitivity
		Gillath et al[42], 2008	ECR	No significant associations
		Gong et al[43], 2020	RAAS	No significant associations
	rs2254298	Costa et al[39], 2009	ASQ	GG higher avoidance
		Chen and Johnson[41], 2012	ECR	GG lower anxiety in females
		Fraley et al[11], 2013	ECR	No significant associations or interactions with maternal sensitivity
		Gong et al[43], 2020	RAAS	No significant associations
	Methylation promoter region	Ebner et al[46], 2019	ECR	Higher methylation associated with higher avoidance
		Ein-Dor et al[47], 2018	AAS	Higher methylation associated with higher avoidance
DRD2	rs1800497	Gong et al[43], 2020	RAAS	A1 homozygotes higher anxiety than A2 carriers
		Fraley et al[11], 2013	ECR	No significant associations or interactions with maternal sensitivity
DRD4	VNTR	Reiner and Spangler[51], 2010	AAI	7R carriers greater security
		Bakermans-Kranenburg et al[52], 2011	AAI	7R carriers greater susceptibility to environmental factors
COMT	rs4680	Erkoreka et al[16], 2018	ECR	ValMet heterozygotes higher avoidance than either homozygotes
5HT1A	rs6295	Gong et al[43], 2020	RAAS	G carriers less comfortable in close relationships
5HT2A	rs6313	Gillath et al[42], 2008	ECR	T homozygotes higher avoidance than C homozygotes
		Salo et al[62], 2011	RSQ	T homozygotes greater susceptibility to environmental factors
		Fraley et al[11], 2013	ECR/RSQ	C homozygotes higher anxiety (RSQ)
5HTTLPR	rs4795541	Caspers et al[64], 2009	AAI	Higher unresolved attachment
		Reiner and Spangler[51], 2010	AAI	No significant associations
		Bakermans-Kranenburg et al[52], 2011	AAI	No significant associations
		Erkoreka et al[16], 2018	ECR	No significant associations
	Methylation promoter region	van IJzendoorn et al[65], 2010	AAI	Higher methylation in L homozygotes increased risk or unresolved loss or trauma; higher methylation in S homozygotes less unresolved loss or trauma
		Jones-Mason et al[66], 2016	AAI	Methylation interacts with socioeconomic status
BDNF	rs6265	Suzuki et al[68], 2012	PBI	Met carriers with low maternal care greater interpersonal sensitivity
		Ibarra et al[69], 2014	PBI	Met carriers greater susceptibility to childrearing style

5HT1A: Serotonin receptor A1; 5HT2A: Serotonin receptor A2; 5HTTLPR: Serotonin transporter-linked polymorphic region; AAI: Adult Attachment Interview; ASQ: Attachment Style Questionnaire; BDNF: Brain-derived neurotrophic factor; COMT: Catechol-o-methyltransferase; CRI: Current Relationship Interview; DRD2: Dopaminergic receptor D2; DRD4: Dopaminergic receptor D4; ECR: Experiences in Close Relationships; OXTR: Oxytocin receptor; PBI: Parental Bonding Instrument; RAAS: Revised Adult Attachment Scale; RSQ: Relationship Questionnaire.