title: Developmental aspects of cortical excitability and inhibition in depressed and healthy youth: an exploratory study.
abstract: OBJECTIVE
  The objective of this post-hoc exploratory analysis was to examine the relationship between age and measures of cortical excitability and inhibition.
  
  
  METHODS
  Forty-six participants (24 with major depressive disorder and 22 healthy controls) completed MT, SICI, ICF, and CSP testing in a cross-sectional protocol. Of these 46 participants, 33 completed LICI testing. Multiple linear robust regression and Spearman partial correlation coefficient were used to examine the relationship between age and the TMS measures.
  
  
  RESULTS
  In the overall sample of 46 participants, age had a significant negative relationship with motor threshold (MT) in both the right (r s = -0.49, adjusted p = 0.007; β = -0.08, adjusted p = 0.001) and left (r s = -0.42, adjusted p = 0.029; β = -0.05, adjusted p = 0.004) hemispheres. This significant negative relationship of age with MT was also observed in the sample of depressed youth in both the right (r s = -0.70, adjusted p = 0.002; β = -0.09, adjusted p = 0.001) and left (r s = -0.54, adjusted p = 0.034; β = -0.05, adjusted p = 0.017) hemispheres, but not in healthy controls. In the sample of the 33 participants who completed LICI testing, age had a significant negative relationship with LICI (200 ms interval) in both the right (r s = -0.48, adjusted p = 0.05; β = -0.24, adjusted p = 0.007) and left (r s = -0.64, adjusted p = 0.002; β = -0.23, adjusted p = 0.001) hemispheres. This negative relationship between age and LICI (200 ms interval) was also observed in depressed youth in both the right (r s = -0.76, adjusted p = 0.034; β = -0.35, adjusted p = 0.004) and left (r s = -0.92, adjusted p = 0.002; β = -0.25, adjusted p = 0.001) hemispheres.
  
  
  CONCLUSIONS
  These findings suggest that younger children have higher MTs. This is more pronounced in depressed youth than healthy controls. LICI inhibition may also increase with age in youth.
authors.affiliation: Division of Child and Adolescent Psychiatry, Department of Psychiatry and Psychology, Mayo Clinic Rochester, MN, USA.
authors.forename: Paul E
authors.initials: PE
authors.lastname: Croarkin
authors.affiliation: Division of Biostatistics, Department of Clinical Sciences, UT Southwestern Medical Center Dallas, TX, USA ; Department of Psychiatry, UT Southwestern Medical Center Dallas, TX, USA.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Nakonezny
authors.affiliation: Division of Child and Adolescent Psychiatry, Department of Psychiatry and Psychology, Mayo Clinic Rochester, MN, USA.
authors.forename: Charles P
authors.initials: CP
authors.lastname: Lewis
authors.affiliation: Division of Child and Adolescent Psychiatry, Department of Psychiatry and Psychology, Mayo Clinic Rochester, MN, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zaccariello
authors.affiliation: Division of Child and Adolescent Psychiatry, Department of Psychiatry and Psychology, Mayo Clinic Rochester, MN, USA.
authors.forename: John E
authors.initials: JE
authors.lastname: Huxsahl
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Duke University School of Medicine Durham, NC, USA.
authors.forename: Mustafa M
authors.initials: MM
authors.lastname: Husain
authors.affiliation: Department of Psychiatry, UT Southwestern Medical Center Dallas, TX, USA.
authors.forename: Betsy D
authors.initials: BD
authors.lastname: Kennard
authors.affiliation: Department of Psychiatry, UT Southwestern Medical Center Dallas, TX, USA.
authors.forename: Graham J
authors.initials: GJ
authors.lastname: Emslie
authors.affiliation: Department of Psychiatry, Centre for Addiction and Mental Health, University of Toronto Toronto, ON, Canada.
authors.forename: Zafiris J
authors.initials: ZJ
authors.lastname: Daskalakis
keywords: CSP; ICF; LICI; SICI; TMS; adolescents; depression; neurodevelopment