Causal relationship between ADHD and frozen shoulder: Two-sample Mendelian randomization

Area of Science:

• Medical Genetics
• Psychiatry
• Orthopedics

Background:

• Attention deficit and hyperactivity disorder (ADHD) is a common neurodevelopmental disorder.
• Frozen shoulder (adhesive capsulitis) is a debilitating condition characterized by shoulder stiffness and pain.
• The potential causal link between ADHD and frozen shoulder remains underexplored.

Purpose of the Study:

• To investigate the potential causal relationship between ADHD and frozen shoulder.
• To determine if ADHD is a risk factor for developing frozen shoulder using genetic data.
• To leverage Mendelian randomization to explore this association.

Main Methods:

• Utilized a two-sample Mendelian randomization (MR) approach.
• Selected independent genetic loci associated with ADHD and frozen shoulder from large-scale genome-wide association studies (GWAS) in European ancestry populations.
• Employed inverse variance weighting, weighted median, and MR-Egger methods for causal inference, with sensitivity analyses including leave-one-out.

Main Results:

• Inverse variance weighting analysis indicated a statistically significant causal effect of ADHD on frozen shoulder (OR: 1.12, 95% CI: 1.00-1.25, P = .046).
• No significant heterogeneity or multiplicity was detected.
• Sensitivity analyses confirmed the robustness of the findings.

Conclusions:

• ADHD is identified as a significant risk factor for the development of frozen shoulder.
• Individuals diagnosed with ADHD exhibit an increased predisposition to suffering from frozen shoulder.
• These findings highlight a potential genetic link and inform clinical considerations for patients with ADHD.