Özcan 2004.

Methods	A cohort study comparing time domain heart rate variability in non‐ADHD controls and ADHD cases treated with methylphenidate for 12 weeks
Participants	Number of participants screened: not stated Number of participants included: 73 Number included as cases (ADHD): 42 Number included as controls (non‐ADHD): 31 ADHD group Number of participants followed up: 42 Number of withdrawals: 0 Diagnosis of ADHD: DSM‐IV (subtype: not stated) Age: mean 11.1 years old (range 6‐15) Sex: 34 males, 8 females IQ: above 70 Country: Turkey Setting: Ethnicity: not stated Methylphenidate‐naïve: not stated Comorbidity: not stated Comedication: no Sociodemographics: not stated Inclusion criteria: ADHD based on DSM‐IV Age 6‐15 years old Exclusion criteria: Psychotic disorder, autistic disorder, hearing and visual problems and mental retardation
Interventions	Methylphenidate type: not stated Mean methylphenidate dosage: 10 mg (2 x 5 mg) Administration schedule: not stated Duration of treatment: 12 weeks Treatment compliance: not stated
Outcomes	Non‐serious adverse events: heart rate variability
Notes	Sample calculation: not stated Ethics approval: yes Funding/vested interests: not stated Authors' affiliations: no affiliations to pharmaceutical companies stated Key conclusions of the study authors: methylphenidate decreased the time domain HRV parameters in ADHD group. Therefore, close cardiac follow‐up is necessary for the detection of side effects of methylphenidate especially in patients who are under risk for developing cardiac arrhythmias and in patients using methylphenidate together with drugs affecting central nervous system Exclusion of methylphenidate non‐responders/children who have previously experienced adverse events on methylphenidate: no Supplemental information regarding IQ has not been possible to receive through personal email correspondence with the authors. Emails sent twice to several of the authors

ADD: attention deficit disorder; ADD‐H: attention deficit disorder with hyperactivity; ADHD: attention deficit hyperactivity disorder; AE: adverse event;bpm: beats per minute; CGI‐S: Clinical Global Impression‐Severity; CI: confidence interval; CK: cytokine; CNS: central nervous system; C‐SSRS: Columbia Suicide Severity Rating Scale; DBP: diastolic blood pressure; DSM‐III‐R: Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised; DSM‐IV: Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition; DSM‐IV‐TR: Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Text Revision; DSM‐5: Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition;ECG: electrocardiogram; ED: emergency department; EEG: electroencephalogram; EF: ejection fraction; EKG: electrocardiogram; FDA: Food and Drug Administration; ER: extended release; HCL: hydrochloride; HRQoL: health‐related quality of life; ICD: International Classification of Diseases; IQ: intelligence quotient; IQR: interquartile range; IR: immediate release; IRR: interrater reliability;ITT: intention‐to‐treat; LLC: limited liability company; LOCF: last observation carried forward; LTFU: loss to follow‐up; MAOI: monoamine oxidase inhibitors; MedDRA: Medical Dictionary for Regulatory Activities; MPH: methylphenidate; MPT: methylphenidate trial; MRI: magnetic resonance imaging; MTA: Multimodal Treatment Study of Children With ADHD; MTS: methylphenidate transdermal system; NICE: National Institute for health and Care Excellence; NNTB: number needed to treat for an additional beneficial outcome; OCD: obsessive compulsive disorder; ODD: oppositional defiant disorder; OROS: osmotic Release Oral System; PDD: pervasive developmental disorder; PTS: placebo transdermal system; PTSD: post‐traumatic stress disorder; RCT: randomised controlled trial; SD: standard deviation; SERS: Side Effects Rating Scale; SBP: systolic blood pressure; SODAS: spheroidal oral drug absorption system; SSRI: selective serotonin reuptake inhibitors; WISC: Wechsler Intelligence Scale for Children.