Table 1.
Studies about biochemical correlates of IGD.
| Reference | Participants | Main Findings |
|---|---|---|
| [42] Kim S. H. et al. (2011) | IAD patients N = 9 (M); Mean age = 22.60 ± 1.16. HC N = 7 (M); Mean age = 23.14 ± 0.67. Assessed with IAT and IADDC. |
A significant reduction of DA D2 receptors availability in the bilateral caudate and left putamen along with an inverse correlation between the severity of the addiction and the degree of dopamine receptor availability. Method: PET scan with [11C] raclopride |
| [44] Hou H. et al. (2012) | IAD patients N = 5 (M); mean age = 20.40 ± 2.30. HC N = 9 (M); mean age = 20.44 ± 1.13 years. Assessed with IADQ and IADDC. |
A significant decrease of DAT expression level of striatum. Method: SPECT with 99mTc-TRODAT-1 |
| [43] Tian M. et al. (2014) | IGD patients N = 12 (M); mean age = 23.50 ± 2.58. HC N = 14 (M); mean age = 22.71 ± 1.27. Assessed with IAT. |
Lower-11C-NMSP binding levels in the right inferior temporal gyrus in the resting state and, after the Internet gaming task, lower binding levels in the putamen. IGD group: A significant decrease in glucose metabolism in the bilateral superior temporal poles and right orbitofrontal gyrus, but a significant increase in the right supplementary motor area, right middle cingulum, and left superior medial frontal cortex, in the resting state. After the Internet gaming task, a significant decrease in the metabolism in the right rectus, the right orbital part of the inferior frontal cortex, and the left orbital part of the superior frontal cortex. Method: PET and 11C-N-methylspiperone and 18F-fluoro-D-glucose |
| [45] Ariatama B. et al. (2019) | IGD patients N = 48; F = 2; M = 46. Assessed with IGDS9-SF. |
IGD group: Lower DAT concentration and a strong opposite correlation between IGD and DAT levels. |
| [48] Liu M. & Lou J. (2015) | IAD patients N = 33; F = 5; M = 28; mean age = 16.58 ± 2.29. HC N = 33; F = 5; M = 28; mean age = 16.58 ± 2.29. Assessed with IAT. |
IGD group: A significantly higher DA plasma level, positively correlated with the IAT score and the weekly online time. |
| [49] Zhang H-X. et al. (2013) | IGD patients N = 20; F = 2; M = 18; mean age = 16.86 ± 1.8. HC N = 15; F = 2; M = 13; mean age = 18.16 ± 2.7. Assessed with DQIA. |
IGD group: A lower mean level of NE but no significant difference in the levels of 5-HT and DA. |
| [50] Kim N. et al. (2016) | IGD patients N = 118 (M); mean age = 16.64 ± 1.13. HC N = 112 (M); mean age = 16.63 ± 0.89. Assessed with OGASA. |
IGD group: Significantly lower plasma levels of Epi and NE, and not significantly higher levels of DA. Slight negative correlation between daily Internet gaming time and plasma NE levels. |
| [34] Paik S-H. et al. (2018) | IGD patients N = 26 (M); mean age = 28.16 ± 5.235. HC N = 23 (M); mean age = 28.16 ± 5.235. Diagnosed according to DMS-5. |
IGD group: Lower glutamate concentrations and no difference in DA serum levels. |
| [57] Kim E. H. & Kim N. H. (2013) | IGD patients N = 78 (M). HC N = 62 (M). |
Significantly higher serum cortisol and ACTH levels. |
| [58] Geisel O. et al. (2015) | IGD patients N = 11(M); mean age = 27.5 ± 5.2. HC N = 10 (M); mean age = 30.5 ± 5.6. PG N = 14 (M); mean age = 35.4 ± 9.5. HC N = 13(M); mean age = 35.2 ± 8.4 Diagnosed according to DSM-5 and ICD-10. |
No differences were found in the cortisol, ACTH and copeptin plasma levels. |
| [59] Bibbey A. et al. (2015) | IGD patients N = 17; F = 12; M = 5; mean age = 19.8 ± 1.29. AUD patients N = 28, F = 15; M = 13; mean age = 19.2 ± 0.67. Comorbid patients N = 17; F = 13; M = 4; mean age = 22.3 ± 2.32. HC N = 26; F = 28; M = 8; mean age = 20.5 ± 2.94. Assessed with IAT and PIUS. |
Neither problematic Internet behaviour nor excessive alcohol consumption, either individually or in combination, were associated with blunted cardiovascular or cortisol stress reactions. |
| [60] Kaess M. et al. (2017) | IGD patients N = 24 (M); mean age = 18.38 ± 3.39 HC N = 25 (M); mean age = 19.68 ± 3.4. Assessed with CSV-S. |
Attenuated cortisol response in IGD during a standardized laboratory stress task. |
| [61] Geisel O. et al. (2018) | IGD patients N = 11 (M); mean age = 27.5 ± 5.1. PG patients N = 14 (M); mean age = 35.4 ± 9.5. AUD patients N = 39 (M); mean age = 45.9 ± 7.3. HC N = 12 (M); mean age = 36.6 ± 8.3. Diagnosed according to DSM-5 and ICD-1. |
Leptin plasma levels of the patients did not differ between the groups. In patients with IGD, leptin plasma levels were positively correlated with BDNF serum levels. |
| [63] Koenig J. et al. (2019) | IGD patients N = 31 (M); mean age = 18.77 ± 3.01. HC N = 31(M); mean age = 20.06 ± 2.94. Diagnosed according to DSM-5. |
No evidence for altered hair hormones, including cortisol, cortisone, testosterone, progesterone, DHEA, and corticosterone, was found in patients with IGD Method: liquid chromatography-mass spectrometry |
| [64] Choi M. R. et al. (2020) | IGD patients N = 33; F = 7; M = 26; mean age = 15.18 ± 0.31. HC N = 40; F = 10; M = 30; mean age = 15.08 ± 0.24. Diagnosed according to DSM-5. |
The expression levels of orexin A and melatonin were significantly elevated in IGD; oxytocin levels tended to be higher but the difference was not statistically significant. The expression levels of cortisol did not differ between the groups. The expression levels of BDNF, sICAM-1, RANTES, and NCAM did not differ between the groups. Internet gaming time was significantly negatively correlated with BNDF expression levels and positively correlated with sICAM-1 expression levels. Method: Human Neuropeptide Magnetic Bead Panel, Human Circadian/Stress Magnetic Bead Panel, Human Neurodegenerative Disease Magnetic Bead Panel 3 |
| [15] Park H. S. et al. (2010) | IGD patients N = 11 (M); mean age = 23.5 ± 2.9. HC N = 9 (M); mean age = 24.7 ± 2.4. Assessed with IGS. |
A significant increase in resting glucose metabolism in the right middle orbitofrontal gyrus, the left caudate nucleus, and the right insula and a significant decrease in glucose metabolism in the bilateral postcentral gyrus, the left precentral gyrus, and the right superior parietal lobule, as well as in the right superior occipital gyrus and the left inferior occipital gyrus. Method: 18F-fluorodeoxyglucose PET scan |
| [74] Geisel O. et al. (2013) | IUD patients N = 11 (M); mean age = 27.57 ± 5.1. HC N = 10 (M); mean age = 30.57 ± 5.6. Diagnosed according to DSM-5. |
No difference in BDNF serum levels between the two groups. |
| [79] Jeong J-E. et al. (2019) | IGD patients N = 19 (M); mean age = 31.2 ± 8.0. HC N = 19 (M); mean age = 31.3 ± 4.2. Assessed with IAT. |
IGD group: Lower GDNF plasma levels; negative correlation between GDNF levels and IAT score. |
| [82] Han D. H. et al. (2014) | PGA patients N = 73; F = 5; M = 68; mean age = 20.6 ± 5.1. HC N = 38; F = 3; M = 35; mean age = 22.0 ± 5.2. Assessed with YIAS, BDI, WSCT. |
IGD group: Decreased levels of NAA in right frontal cortex and decreased levels of Cho in the right temporal cortex. Negative correlation between NAA levels and IAS, WSCT scores. Negative correlation between levels of Cho in the right temporal cortex and BDI score. Method: structural MR and 1H-MRS |
| [83] Cho Y. U. et al. (2017) | IGD patients N = 24 (M); mean age = 23.7 ± 2.3. HC N = 28 (M); mean age = 23.7 ± 2.3. Assessed with IAT. |
IGD group: Decreased levels of myo-inositol, arabitol, and glyceric acid. A positive correlation between Internet addiction severity score and aspartate, pyrrole-2-carboxylic acid, cholic acid, uracil, and nicotinamide levels and a negative correlation one with sugar alcohols and common fatty acids. Altered valine-leucine-isoleucine and glycine-serine-threonine pathways. |
| [85] Lee M. et al. (2018) | IGD patients N = 25. HC N = 26. Diagnosed according to DSM-5. |
IGD group: Significantly lower expression of three miRNAs (hsa-miR-200c-3p, hsa-miR-26b-5p, and hsa-miR-652-3p) reported to be involved in many neuropsychiatric disorders. Method: TaqMan Low Density miRNAArray |
| [93] Han D. H. et al. (2007) | EIGP subjects N = 79 (M); mean age = 16.08 ± 0.66. HC N = 75 (M); mean age = 16.07 ± 0.68. Assessed with IAS, RD |
EIGP group: The DRD2 Taq1A1/A1 genotype was more frequent and the frequency of genotypes containing DRD2 Taq1A1 was higher. COMT genotype did not differ, but the frequency of genotypes containing COMTL was higher. Positive correlation between RD score and the presence of DRD2 Taq1A1. |
| [97] Lee Y. S. et al. (2008) | EIU patients N = 91 (M); mean age = 16.1 ± 0.7. HC N = 75 (M); mean age = 16.1 ± 0.7. Assessed with IAS. |
EIU group: Higher prevalence of the homozygous short allelic variant of the serotonin transporter gene (SS-5HTTLPR). |
| [100] Montag C. et al. (2012) | IGD patients N = 132; F = 52; M = 80; mean age = 23.92 ± 5.23. HC N = 132; F = 52; M = 80; mean age = 23.92 ± 5.23. Assessed with IAT. |
IGD group: The T-variant occurred significantly more frequently. |
| [105] Jeong J-E. et al. (2017) | IGD patients N = 30 (M); mean age = 30.73 ± 6.72. HC N = 30 (M); mean age = 30.57 ± 5.48). Assessed with IAT. |
IGD group: Lower numbers of the T allele of rs1044396 in the nicotinic acetylcholine receptor alpha 4 subunit (CHRNA4). |
| [106] Park J. et al. (2018) | IGD patients N = 118 (M); mean age = 16.63. HC N = 112 (M); mean age = 16.63. Assessed with KADO scale. |
No difference in the DRD4 and DAT1 VNTR polymorphisms and in the NET8 (rs5569) or CHRNA4 (rs1044396) genes. Increased frequency of the AA genotype of CRHR1 (rs28364027) in the IGD group. |
| [108] Kim N. et al. (2019) | IGD patients N = 118 (M); mean age = 16.64 ± 1.13. HC N = 112 (M); mean age = 16.63 ± 0.89. Assessed with OGASA. |
IGD group: Leukocyte telomere length is significantly shorter and is positively correlated to Epi and NE levels. |
Beck Depressive Inventory: BDI; Internet Addiction Test: IAT; Internet Addictive Disorder Diagnostic Criteria: IADDC; Internet Addiction Diagnostic Questionnaire: IADQ; Diagnostic Questionnaire for Internet Addiction: DQIA; Online Game Addiction Scale for Adolescents: OGASA; Pathological Internet use scale: PIUS; Scale for the Assessment of Pathological Computer-Gaming: CVS-S; Korean Internet Game Addiction Scale: IGS; IAS: Internet Addiction Scale; RD: Reward-Dependence scale; Wisconsin Card Sorting Test: WCST; Young Internet Addiction Scale (YIAS).