Varley 2001.

Methods	A retrospective chart review
Participants	Number of participants screened: 555 Number of participants included: 517 Diagnosis of ADHD: DSM‐IV (subtype: not stated) Age: mean 11 years old (range not stated) IQ: not stated Sex: not stated Methylphenidate‐naïve: not stated Ethnicity: not stated Country: not stated Comorbidity: tics Comedication: no Sociodemographics: not stated Inclusion criteria: ADHD Exclusion criteria: Comedication
Interventions	Methylphenidate type: not stated Mean methylphenidate dosage: not stated Administration schedule: not stated Duration of intervention: not stated Treatment compliance: not stated
Outcomes	Non‐serious adverse events Retrospective review of medical records. It was recorded whether the participants did or did not have a reported history of tic emergence in the course of pharmacologic treatment in that clinic. 8.3% (31 of 374) of participants treated with methylphenidate developed tics
Notes	Sample calculation: no Ethics approval: not stated Funding/vested interest: supported by a National Institutes of Health Biomedical Research Support Grant, 1991 Authors' affiliations: not stated Key conclusions of the study authors: tics was not related to dose nor treatment length, and may not be related to stimulants Exclusion of methylphenidate non‐responders/children who have previously experienced adverse events on methylphenidate: not stated Supplemental information requested through personal email correspondence with the authors in April 2014. No reply