title: The relationship between second-to-fourth digit (2D:4D) ratios and problematic and pathological Internet use among Turkish university students.
abstract: Background and aims The ratio of the second and fourth fingers (2D:4D ratio) is a sexually dimorphic trait, with men tending to have lower values than women. This ratio has been related to prenatal testosterone concentrations and addictive behaviors including problematic video-gaming. We aimed to investigate the possible association between 2D:4D ratios and Internet addiction and whether such a relationship would be independent of impulsivity. Methods A total of 652 university students (369 women, 283 men), aged 17-27 years, were enrolled in the study. Problematic and pathological Internet use (PPIU) was assessed using the Internet Addiction Test (IAT). The participants also completed the Barratt Impulsiveness Scale (version 11; BIS-11) and had their 2D:4D ratios measured. Results 2D:4D ratios were not significantly different in women with PPIU and in those with adaptive Internet use (AIU). Men with PPIU exhibited lower 2D:4D ratios on both hands when compared with those with AIU. Correlation analysis revealed that 2D:4D ratios on both hands were negatively correlated with IAT scores among men, but not among women. The multiple linear regression analysis revealed that age, duration of weekly Internet use, impulsiveness, and 2D:4D ratios on the right hand were independently associated with IAT scores among men, and impulsivity did not mediate the relationship between 2D:4D ratios and PPIU. Conclusions For men, 2D:4D ratios on the right hand were inversely correlated with Internet addiction severity even after controlling for individual differences in impulsivity. These findings suggest that high prenatal testosterone levels may contribute to the occurrence of PPIU among men.
authors.affiliation: 1 Department of Psychiatry, Yale School of Medicine , New Haven, CT, USA.
authors.forename: Fatih
authors.initials: F
authors.lastname: Canan
authors.affiliation: 2 Department of Psychiatry, Akdeniz University School of Medicine , Antalya, Turkey.
authors.forename: Servet
authors.initials: S
authors.lastname: Karaca
authors.affiliation: 3 Akdeniz University School of Medicine , Antalya, Turkey.
authors.forename: Melike
authors.initials: M
authors.lastname: Düzgün
authors.affiliation: 3 Akdeniz University School of Medicine , Antalya, Turkey.
authors.forename: Ayşe Merve
authors.initials: AM
authors.lastname: Erdem
authors.affiliation: 3 Akdeniz University School of Medicine , Antalya, Turkey.
authors.forename: Esranur
authors.initials: E
authors.lastname: Karaçaylı
authors.affiliation: 3 Akdeniz University School of Medicine , Antalya, Turkey.
authors.forename: Nur Begüm
authors.initials: NB
authors.lastname: Topan
authors.affiliation: 4 Department of Psychiatry, Hallym University Medical Center, Chuncheon Sacred Heart Hospital , Chuncheon, South Korea.
authors.forename: Sang-Kyu
authors.initials: SK
authors.lastname: Lee
authors.affiliation: 1 Department of Psychiatry, Yale School of Medicine , New Haven, CT, USA.
authors.forename: Zu Wei
authors.initials: ZW
authors.lastname: Zhai
authors.affiliation: 2 Department of Psychiatry, Akdeniz University School of Medicine , Antalya, Turkey.
authors.forename: Murat
authors.initials: M
authors.lastname: Kuloğlu
authors.affiliation: 1 Department of Psychiatry, Yale School of Medicine , New Haven, CT, USA.|5 The National Center on Addiction and Substance Abuse, Yale School of Medicine , New Haven, CT, USA.|6 The Connecticut Mental Health Center , New Haven, CT, USA.|7 Department of Neuroscience and Child Study Center, Yale School of Medicine , New Haven, CT, USA.
authors.forename: Marc N
authors.initials: MN
authors.lastname: Potenza
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D016739:Behavior, Addictive / Q000175:diagnosis / Q000473:pathology* / Q000523:psychology; D005260:Female; D005385:Fingers / Q000473:pathology*; D006801:Humans; D007175:Impulsive Behavior; D020407:Internet; D016014:Linear Models; D008297:Male; D011569:Psychiatric Status Rating Scales; D012720:Severity of Illness Index; D012727:Sex Characteristics; D013334:Students; D013739:Testosterone / Q000378:metabolism; D014495:Universities; D055815:Young Adult
chemical_list: D013739:Testosterone
keywords: 2D:4D; Internet addiction; digit ratio; impulsivity; testosterone