| Gene | Chromosome | Function | Reference | ASD | ADHD |
| FMR1 (including premutation) | Xq28 | Involved in making fragile X mental retardation 1 protein (FMRP), an RNA-binding protein involved in gene regulation | [150, 151] | [151–153] |
| TSC2 | 16p13 | Actin cytoskeleton dynamics; inactivation of GTPase; neuronal migration and cell differentiation | [154–156] | [157, 158] |
| NF1 | 17q11 | Codes for protein neurofibromin and causally related to neurofibromatosis type 1; associated with inactivation of GTPase; cytoskeleton dynamics | [159, 160] | [161] |
| SHANK3 | 22q13 | Dendrite morphology regulation; synapse scaffolding and plasticity; binding neuroligins | [162, 163] | [164] |
| GRIN2A | 16p13 | Codes for the 2A subunit of the NMDA receptor, which is ligand- and voltage-gated and is involved in long-term potentiation and synaptic transmission | [165] | [134, 166] |
| GABAR | 15q12 | Encodes the GABA receptors and their subunits, thus mediating neurotransmitter inhibitory processes | [167, 168] | [169, 170]b |
| SLC6A4/5HTT/SERT | 17p11 | Encodes the serotonin transporter; mediates reuptake of serotonin from synapses | [171, 172] | [173, 174] |
| SLC6A3/DAT/DAT1 | | Encodes a dopamine transporter; regulates extracellular dopamine and reuptake of dopamine from synapses | [175, 176] | [177, 178] |
| OXTR | 3p25-26 | Encodes the oxytocin receptor and thus mediates the action of oxytocin in various brain regions, particularly those supporting social cognition | [179, 180] | [181]a |
| AVPR1 | 12q14 | Encodes the arginine vasopressin receptor 1a, which mediates cell contraction, proliferation, glycogenolysis, and platelet aggregation | [182, 183] | [184]c |
| SNAP25 | 20p12-p11.2 | Encodes a plasma membrane protein involved in vesicle docking, fusion, and neurotransmitter release | [185, 186] | [178, 187] |
| SLC9A9/NHE9 | | Encodes a sodium/proton exchanger; plays a role in cation homeostasis | [188, 189] | [190–192] |
| HTR1B | 6q13 | Encodes the 5-HT1B receptor, associated with serotonin regulation; depending on location, it is variably involved in modulating serotonin and dopamine in various cortical and noncortical regions | [193] | [194, 195] |
| NLGN4 | Xp22.3 | Encodes protein neuroligin 4, involved in cell adhesion, synapse formation, and mediates transsynaptic signalling | [196, 197] | [198, 199] |
| DRD4 | 11p15.5 | Encodes dopamine receptor D4, a G-protein coupled receptor; upon activation, the receptor inhibits adenylyl cyclase, thus decreasing intracellular cyclic AMP | [200, 201]d | [178, 202] |
| DRD5 | 4p16.1 | Encodes dopamine receptor D5, which is involved in synthesis of cyclic AMP via activation of adenylyl cyclase, and Ca2+ and K+ conductance | [203]e | [178, 204] |
| DRD3 | 3q13.3 | Encodes dopamine receptor D3; activity is mediated by G-proteins which inhibit adenylyl cyclase; promotes cell proliferation | [205, 206] | [207] |
| MAOA | Xp11.3 | Encodes enzymes that deaminate and catabolize neurotransmitters such as dopamine, serotonin, and norepinephrine | [208–210] | [211, 212] |
| COMT | 22q11.21 | Encodes the catechol-O-methyltransferase enzyme, which catabolizes neurotransmitters such as dopamine and norepinephrine | [213, 214] | [215, 216] |
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aFindings should be considered preliminary. bIn this study, OXTR was only associated with social cognition in ADHD and not diagnostic status itself. cIn this study, AVPR1A was associated with executive functioning, not ADHD, although executive functioning is considered a core impairment in ADHD (but also other neurodevelopmental conditions, including autism). dResults may reflect differences in cooccurring symptoms among individuals with ASD as opposed to diagnosis of ASD specifically. eFew studies have shown similar results, so these should be interpreted cautiously.
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