Neurochemical sex differences in adult ADHD patients: an MRS study

OBJECTIVE: Attention-deficit/hyperactivity disorder (ADHD) is a common neurodevelopmental disorder. Relevant sex differences in symptomatology are discussed. This study compared brain neurometabolism in the anterior cingulate cortex (ACC) and left cerebellar hemisphere in age- and IQ-matched adult male (mADHD) and female (fADHD) ADHD patients. METHODS: We studied 48 (ACC) and 42 (cerebellum) male/female pairs of stimulant-free patients with adult ADHD. Single voxel magnetic resonance spectroscopy (MRS) was used to investigate creatine (Cre), total choline (t-Cho), glutamate + glutamine (Glx), N-acetylaspartate, and myo-inositol. The mADHD and fADHD groups were compared using robust linear regression. The level of significance was corrected for multiple tests using the Benjamini-Hochberg approach. RESULTS: For the ACC, the signals of Cre (p = 0.008) and t-Cho (p = 0.004) showed significant effects of the age covariate as well as an interaction of sex and age (Cre: p = 0.033; t-Cho: p = 0.040). For the Glx signal, an interaction of sex and age could also be observed (p = 0.033). For cerebellar neurometabolites, the signals of t-Cho (p = 0.049) and Glx (p = 0.049) showed significant effects of the factor sex. CONCLUSION: This is the largest study yet to analyze sex differences in brain neurochemistry in adult patients with ADHD. Different age-dependent t-Cho signals in the ACC might be associated with delayed myelinization in mADHD. Further MRS studies in adult ADHD, accounting for possible sex effects, are warranted to validate the present findings.