Digit ratio (2D:4D) in relation to substance and computer use: a meta-analysis

Abstract

Human studies have reported inconsistent associations between the length ratio of the second finger to the fourth finger (2D:4D), which is a proxy for prenatal androgen load, and substance or computer use in adolescents and adults. This metaanalysis quantifies the magnitude of this relationship and investigates the roles of sex, definition of caseness, different forms of addiction, the hand measured (right hand versus left hand), and other cohort characteristics. Univariate random-effects meta-analyses were performed, and moderators were tested with Bonferroni-corrected meta-regression analyses. The study included 18 independent samples with a total of 175,955 participants (96,316 males and 79,639 females). There was a significant difference in 2D:4D between the substance and computer-using subjects and the controls for the combined sample (Hedge's g = − 0.178 [− 0.291; − 0.064]) and for males (Hedge's g = − 0.260 [− 0.399; − 0.122]), but not for females. These effects were amplified when only analyzing studies that compared dependent versus non-dependent subjects (combined sample: g = − 0.325 [− 0.492; − 0.157]; males: g = − 0.427 [− 0.564; − 0.291]), but did not reach significance in the subgroup of studies examining other parameters of substance and computer use. When analyzing different forms of substance and computer use separately, alcohol intake and computer use revealed a significant difference in the standardized mean. Again, the effects were amplified when analyzing the subgroup of males and the subgroup of studies comparing dependent versus non-dependent subjects, with effect sizes showing Hedge's g values as many as − 0.552 [− 0.785; − 0.319] (alcohol-dependent males). Thus, this meta-analysis confirms that lower 2D:4D is associated with substance and computer dependency. Further studies are encouraged to explore the link between intrauterine hormone environment and addiction risk.

Lower digit ratio (2D:4D) in alcohol dependence: Confirmation and exploratory analysis in a population‐based study of young men

“…In summary, 2D:4D appears to be associated with the complex trait of alcohol dependence but not with alcohol abuse or mild alcohol use disorder. This agrees with the results of a recent meta‐analysis showing lowered 2D:4D in subjects diagnosed with alcohol dependence according to established diagnostic criteria, but not in those classified by other parameters of alcohol use . We found only a few minor associations between single DSM‐IV/‐5 items and 2D:4D, suggesting that 2D:4D influences alcohol dependence via a complex interaction between multiple behavioral traits rather than a single trait.…”

Basic Human Body Dimensions Relate to Alcohol Dependence and Predict Hospital Readmission

“…Three additional studies on this topic have since been published [25,29,30]. In support of the initial investigation, our recent meta-analysis confirmed lower 2D:4D in alcohol-dependent males with a medium effect size (Hedge's g = −0.552) [31]. Lower 2D:4D has also been shown to predict more alcohol-related 12-month hospital readmissions in alcohol-dependent in-patients [29].…”

Digit ratio (2D:4D) and transgender identity: new original data and a meta-analysis

“…Evaluation of the practical relevance by comparing our results to other meta-analyses in the research field of 2D:4D shows that effect sizes of approximately standardized mean difference = 0.2 are common, e.g. in addictive disorders 13 or physical prowess 18 , but, rarely, higher effects exist as well (e.g. in sexual orientation of women 16 and autism spectrum disorders 14 ).…”

“…We included case-control, cohort, and cross-sectional studies. The eligibility criteria were defined analogously to our meta-analytic review on 2D:4D and substance and computer use 13 and are detailed in our coding protocol (Supplementary Table S5). The literature search was summarized according to the PRISMA guidelines 47 .…”