A recently published two-sample Mendelian randomization study found that genetically predicted leisure screen time may be linked to a 32% lower risk of attention-deficit/hyperactivity disorder and a 66% higher risk of intellectual disability.
Lead study author Chen Cai, MD, and colleagues, of the Hangzhou Linping Women & Children Health Hospital at Zhejiang University, and Lanzhou University, analyzed genome-wide association study data from 703,901 participants of European ancestry across 51 cohorts, including 256,725 in the leisure screen time (LST)-valid data set.
Using the inverse-variance weighted method as the primary approach, the investigators reported an odds ratio (OR) of 0.68 for attention-deficit/hyperactivity disorder (ADHD) and 1.66 for intellectual disability (ID) with each standard deviation increase in LST. Weighted median analysis confirmed these results (ADHD: OR = 0.68, ID: OR = 1.51). No statistically significant causal associations were identified for autism spectrum disorder, learning disability, speech disorder, or Tourette disorder. Outcome data sets included 46,351 individuals for autism spectrum disorder, 21,191 for ADHD, 12,441 for ID via proxy intelligence scores, 408,542 for learning disability, 408,467 for speech disorder, and 456,348 for Tourette disorder.
Sensitivity analyses with Mendelian randomization (MR) Egger, simple mode, and weighted mode, as well as MR-PRESSO and leave-one-out testing, found no evidence of horizontal pleiotropy or heterogeneity across 68 single-nucleotide polymorphisms (SNP) for ADHD and 19 SNPs for ID, supporting the robustness of the findings.
The investigators noted study limitations, including the reliance on European ancestry populations, potential unmeasured confounders, and the use of childhood intelligence as a proxy for ID. They also cautioned that true exposure-outcome relationships may follow nonlinear patterns, such as J-shaped or U-shaped curves, not captured in this analysis.
Disclosure information can be found in the study.
Source: Brain and Behavior
