Table 2.

Functional neuroimaging-genetics studies in ADHD.

Genes	Index variants	Groups	MRI	Imaging matrix	Results	References
SLC6A3	9–6 SLC6A3 haplotype	9–6 haplotype carriers vs. non 9–6 haplotype carriers	fMRI	Rewarded and non‐rewarded trials	Bayesian Constraint-based Causal Discovery (BCCD) algorithm confirmed that there is no direct link between SLC6A3 genetic variability and brain activation, but suggested an indirect link mediated through inattention symptoms and diagnostic status of ADHD.	Sokolova et al.146
	9‐6 SLC6A3 haplotype	SLC6A3 10–6 dosage (2 copies vs. <2 copies)	fMRI	VS and CN activity during reward-predicting cues	ADHD: activation in CN ↓ as a number of copies ↑, but in the control group reverse was found.	Paloyelis et al.143
	3’ UTR VNTR	9R carriers vs. 10R/10R carriers	fMRI	Working memory task	9R carriers: ↓ left medial PFC activation compared to 10R/10R carriers. “Group × genotype interaction showed that 10R/10R-ADHD” “patients had ↑ activity in pre-SMA/dorsal ACC compared” to HC.	Brown et al.183
	3’ UTR VNTR	10R/10R carriers vs. 9R carriers	fMRI	Go/No-Go task	10R/10R carriers: ↑ activity in frontal, medial, and parietal regions during response inhibition compared to 9R carriers; ↓error response in the parahippocampal gyrus.	Braet et al.184
	3’ UTR VNTR	10R/10R carriers vs. 9R carriers	fMRI	Go/No-Go task	10R/10R carriers: ↑ activity in left striatum, right dorsal premotor cortex, and temporoparietal cortical junction compared to 9R carriers.	Bedard et al.144
	3’ UTR VNTR	9R carriers vs. 10R/10R carriers	fMRI	Go/No-Go paradigm	9R carriers: ↑ activity in CN and ↓ in cerebellar vermis compared to 10R/10R carriers. Group × genotype interaction: effect in CN is observed in ADHD and unaffected siblings, but not HC.	Durston et al.185
	3’ UTR VNTR	10R/10R carriers vs. 9R carriers	fMRI	Multi-source interference task	9R carriers: ↓ activity in dorsal ACC compared to 10R/10R carriers.	Brown et al.161
	3’ UTR and intron 8 VNTR haplotype	9–6 haplotype carriers vs. non 9–6 haplotype carriers	fMRI	Striatal activity during reward anticipation task	No differences in striatal activity compared with non 9–6 haplotype carriers nor 9R- and 10R/10R carriers.	Hoogman et al.148
	3’ UTR and intron 8 VNTR haplotype, rs37020, rs460000, rs4680	10–6 haplotype carriers vs. non-10–6 haplotype- carriers; rs37020	fMRI	Stop signal task	No genotype × ADHD interaction effects. SLC6A3 10–6 “haplotype-homozygotes: ↑ activity related to successful” stop-trials in pre-supplementary motor “areas, ↓ activity in superior frontal and temporal pole” areas. “rs37020 AA carriers: ↓ activity during failed stop-trials in IFG,” pre-supplementary motor areas, and postcentral gyrus.	van Rooij et al.158
COMT	rs4680	Met carriers vs. Val/Val carriers	rs-fMRI	Crus I/II in the cerebellum	Met-carriers exhibiting significantly lower functional connectivity than the Val/Val genotype.	Mizuno et al.160
SLC6A4	5-HTTLPR	3 genotype groups per variant	fMRI	Stop signal task	SLC6A4 SS-genotype group: ↓ activation in frontal nodes and “↑ activation in posterior nodes. No associations between SLC6A4 and HTR1B variants and ADHD or ADHD-related neural activation.	van Rooij et al.159
NOS1	exon 1f-VNTR	SS carriers vs. SL/LL carriers	fMRI	Reward anticipation task/modified MID task	SS carriers: ↑ activity in VS. No group × genotype interactions.	Hoogman et al.186
MAOA	rs1137070	TT carriers vs. CC carriers	fMRI	Working memory task	ADHD TT carriers: ↑ activation in the left inferior frontal lobe, pars opercularis.	Ko et al.147
HTR1B	5-HTTLPR, rs6296	3 genotype groups per variant	fMRI	Stop signal task	SLC6A4 SS-genotype group: ↓ activation in frontal nodes and “↑ activation in posterior nodes. HTR1B genotype: associated” with differential activation in anterior cingulate, occipital, inferior temporal, and cerebellar regions during successful stop trials. No associations between SLC6A4 and HTR1B variants and ADHD or ADHD-related neural activation.	van Rooij et al.159