Table 1.

Summary of studies (from the past 10 years) on the effect of pre-gestational and prenatal cannabis exposure on genes and molecular pathways in humans. Studies are in reverse order chronologically by publication year

Reference	Study design	Time of exposure	Cell target	Outcome and platform	Main findings	Developmental significance
Schrott et al. 2019* [72••]	Cross-sectional study n = 24 male, adult subjects; 12 cannabis users and 12 controls	Pre-conception	Sperm of male adult subjects Human conceptal tissue (elective abortions) F0 generation	DNA methylation Quantitative bisulfite pyrosequencing mRNA transcript expression	• Methylation of DLGAP2 intron 7 was inversely correlated with DLGAP2 mRNA expression in human conceptal brain tissue (p-trend < 0.01). • The inverse relationship between DLGAP2 gene methylation and mRNA transcript expression was evident for both males and females, but this relationship was significant only in females (p-trend = 0.006).	• DLGAP2 is involved in synapse organization, neuronal signaling, and strongly implicated in autism spectrum disorder (ASD).
Gerra et al. 2018 [41••]	Nested case-control study n = 136 subjects ages 18–60 years; 40 cannabis users and 96 controls	Pre-conception	Peripheral whole blood of adult subjects F0 generation	DNA methylation Methylated DNA immunoprecipitation (MeDIP)-qPCR	• DNA methylation higher in cannabis users compared to control subjects in exon 8 of DRD2 gene at + 66.7 kb from transcription start site (TSS) (p = 0.034) and CpG region at + 3 kb from TSS of NCAM1 gene (p = 0.0004). • No difference in cannabis users compared to control subjects in DNA methylation at ANKK1 − 0.25 kb, DRD2 − 0.4 kb and + 0.9 kb, NCAM1 + 0.4 kb, CBR1 + 22.31 kb.	• DRD2 and NCAM1 play central role in dopaminergic pathway. • Increased methylation of DRD2 and NCAM1 may reflect lower mRNA expression. • Lower availability of DRD2 receptors could underly reward deficit condition. • NCAM1 implicated in developmental functions and nervous system maintenance.
Murphy et al. 2018* [28••]	Cross-sectional study n = 24 male, adult subjects; 12 cannabis users and 12 controls	Pre-conception	Sperm of male adult subjects F0 generation	DNA methylation Reduced representation bisulfite sequencing (RRBS)	• 6640 CpG sites differed (p < 0.05) between cannabis users and non-users. • Majority of CpGs (78.3%) had lower levels of methylation in user group. • DGLAP2 hypomethylated in user group. • Maximum # CpG sites differentially methylated for given gene was for Aryl Hydrocarbon Receptor Repressor (AHRR) (94 CpGs hypomethylated ≥ 10% among users). • PTG1R methylation inversely correlated with Δ9-THC level (R2 = 0.839, p = 1.97e-4). • Increased CSNK1E methylation associated with increased Δ9-THC (R2 = 0.686, p = 0.003).	• DNA methylation changes of non-imprinted genes in gametes can resist post-fertilization reprogramming and persist in somatic cells of the offspring, including the brain. • DGLAP2 gene encodes membrane associated protein involved in synapse organization and signaling in neuronal cells and is linked to schizophrenia. • PTG1R, which encodes the Prostaglandin I2 Receptor (a powerful vasodilator), associated with reduced sperm fecundity. • CSNK1E, which encodes the Casein Kinase 1 Epsilon, phosphorylates circadian clock protein PER2 and is implicated in sensitivity to opioids.
Fransquet et al. 2017 [62•]	Nested case-control study n = 804 maternal subjects; 44 cannabis users anytime during pregnancy and 760 non-user controls	Prenatal	Buccal cells of neonates of maternal subjects F1 generation	DNA methylation SEQUENOM MassARRAY	• Gestational cannabis use associated with increased methylation at one CpG site tested in DRD4 (CpG.21.22.2) (β + 1.48, 95% CI: 0.02–2.93, p = 0.047). • At CpG.32, weak evidence that gestational cannabis is associated with increased methylation when adjusting for other substance use (β + .67, 95% CI: − 0.12-1.46, p = 0.09). • No associations remained significant after correction for multiple testing using a Bonferroni corrected significance level of 0.0026 given the 19 CpG units examined.	• DRD4 plays key role in dopamine signaling and is associated with drug use. • Increased DRD4 methylation in saliva has been associated with increased severity of ADHD symptoms in children. • Tissue specificity (using buccal cells instead of brain tissue) could have contributed to the null findings.
DiNieri et al. 2011* [55]	Case-control study n = 25 no maternal cannabis use and n = 24 maternal cannabis use	Prenatal	Fetal brain specimens (18–22 weeks of gestation) (elective abortions) F1 generation	Gene expression (mRNA)	• Decreased DRD2 mRNA expression in NAc in brain specimens with maternal cannabis exposure (p = 0.003). • DRD2 mRNA levels negatively correlated with maternal report of cannabis use (r = − 0.42, p = 0.005). • DRD2 mRNA expression was not altered in putamen with cannabis exposure (p = 0.736). • DRD1 mRNA levels were not altered in the NAc with cannabis exposure (p = 0.330). • PDYN mRNA expression was not altered with cannabis exposure (p = 0.155). • PENK mRNA expression was not altered with cannabis exposure.	• DRD2 dysregulation implicated in addiction risk. • Cannabis could increase vulnerability to addiction and other psychiatric disorders by disrupting DRD2 gene expression.