Associations of the gut microbiome and inflammatory markers with mental health symptoms: a cross-sectional study on Danish adolescents

Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder that often persists into adulthood and is accompanied by comorbid mental health problems. This cross-sectional cohort study analyzed 411 18-year-olds from the Danish COPSAC(2000) birth cohort to investigate the relationship between the gut microbiome, fasting and postprandial systemic inflammation, ADHD symptoms, and symptoms of anxiety, stress, and depression. ADHD was assessed using the Adult ADHD Self-Report Scale (ASRS), while depression, stress, and anxiety were evaluated with the Depression, Anxiety, and Stress Scale 21 (DASS-21). Fecal metagenomic data and inflammation levels, measured as glycosylated protein A (GlycA), were analyzed following a standardized meal challenge. In males, higher ADHD symptom scores correlated significantly with increased abundance of a tryptophan biosynthesis pathway (MetaCyc Metabolic Pathways Database) and elevated fasting and postprandial GlycA levels (p < 0.05). While the severity of depression, anxiety, and stress symptoms showed weak associations with GlycA and the gut microbiome, our findings indicate a significant link between ADHD symptoms and postprandial inflammation, warranting further investigation into underlying mechanisms.