Table 1.

Epigenome-wide association studies of mental health traits and diseases conducted in peripheral blood. A semi-systematic PubMed search was undertaken (access date 21/11/2018) using the terms ‘DNA methylation’, ‘methylome-wide’, ‘epigenome-wide’, ‘psychiatry’, ‘psychiatric’, ‘behaviour’ and ‘human’. FDR: false discovery rate; DMR: differentially methylated regions.

Trait/Disease	Study Design	Tissue	Sample Size	DNA Methylation Differences	Significance Threshold	Reference
Wellbeing	Population study	Blood	N = 2456	2 CpGs	Bonferroni p < 0.05	[4]
Schizophrenia	Case-control	Blood	N = 1339 (discovery); N = 497 (replication)	923 CpGs	FDR p < 0.2	[1]
Substance abuse	Population study	Cord blood	N = 244	65 CpGs	FDR q < 0.05	[12]
Suicidal behaviour	Case-control	White blood cells	N = 123	None below threshold	Not specified	[2]
Post-traumatic stress disorder	Clinical study (trauma patients)	Blood	N = 473	None below threshold	FDR p < 0.05	[7]
Major depressive disorder	Case-control	Blood	N = 473	None below threshold	FDR p < 0.05	[7]
Panic disorder	Case-control	Blood	N = 96	40 CpGs	FDR p < 0.05	[5]
Educational attainment	Population study	Blood	N = 10767	9 CpGs	p < 1 × 10−7	[21]
Mesial temporal lobe epilepsy	Case-control	Blood	N = 60	216 CpGs	p < 1.03 × 10−7	[18]
Parkinson’s disease	Case-control	Peripheral blood mononuclear cells	N = 38	2 CpGs (identified via multiple methods)	methylation difference >15% and validation with other methods	[20]
Attention-deficit hyperactivity disorder	Population study	Cord blood	N = 828	13 CpGs	FDR q < 0.05	[9]
Oppositional defiant disorder	Population study	Cord blood	N = 671	30 CpGs	FDR q < 0.05	[10]
Depression	Case-control	Blood	N = 200	6 DMRs	Sidak corrected p < 0.05	[22]
Cognitive abilities	Population study	Blood	N = 2557–6809	2 CpGs	p < 0.05/(420000 CpG x7 traits)	[8]
Depressive symptoms	Case-control	Blood	N = 47	None below threshold		[6]
Depressive symptoms	Population study	Blood	N = 7948 (discovery); N = 3308 (replication)	3 CpGs	p < 1.03 × 10−7	[3]
Narcolepsy	Case-control	Blood	N = 46	14 CpGs	FDR p < 0.05	[19]
Violent aggression	Clinical study (schizophrenia patients)	Peripheral blood mononuclear cells	N = 134 (discovery)	Weak differences	p < 1 × 10−6	[15]
Physical aggression	Population study	Buccal (discovery); peripheral T cells (replication)	N = 119 (discovery); N = 38 (replication)	4 CpGs; 2 DMRs	FDR q < 0.05	[14]
Early-onset conduct disorder	Case-control	Cord blood	N = 260	7 CpGs	FDR q < 0.05	[13]
Multiple risk behaviours	Population study	Blood	N = 227–575	2 CpGs	FDR q < 0.10	[11]
Autism spectrum disorder	Case-control	Blood	N = 1311	None below threshold	p < 1.12 × 10−7	[16]
Autism spectrum disorder	Case-control	Cord blood	N = 1263	None below threshold	p < 1 × 10−7	[17]