Zeni 2007.

Methods	A cohort study of methylphenidate use for 1 month
Participants	Number of participants screened: 111 Number of participants included:106 Number of participants followed up: not stated Number of withdrawals: 5 Diagnosis of ADHD: DSM‐IV (subtype: combined (58.5%), hyperactive‐impulsive (7.5%), inattentive (26.4%)) Age: mean 10.26, range 4‐17 years old IQ: not stated Sex: 82 males, 24 females Methylphenidate‐naïve: 100% Ethnicity: 100% European‐Brazilian Country: Brazil Setting: outpatient clinic Comorbidity: conduct disorder (16%), oppositional defiant disorder (51.9%), mood disorders (9,4%), anxiety disorders (23.8%) Comedication: none Sociodemographics: not stated Inclusion criteria ADHD diagnosis according to DSM‐IV Age between 4 and 17 years old European‐Brazilian ethnicity Drug naïve for methylphenidate Prescribed dose of methylphenidate of 0.3 mg/kg/day
Interventions	Methylphenidate type: short acting Mean methylphenidate dosage: 0.5 mg/kg/day Administration schedule: not stated Duration of intervention: 1 month Treatment compliance: 2 patients excluded due to irregular use of methylphenidate
Outcomes	Non‐serious adverse events Barkley SERS: Sleep (insomnia): absent: 77 (72.6%); present: 21 (19.8%); information missing: 8 (7.5%) Decreased appetite: absent: 44 (41.5%); present: 53 (50%); information missing: 9 (8.5%)
Notes	Sample calculation: no Ethics approval: yes Funding/vested interest: governmental agencies: Conselho Nacional de Desenvolvimento Cientıfico e Tecnologico (CNPq, Brazil); Grant number: 471761/03‐6; Grant sponsor: Programa de Apoio a Nucleos de Excelencia (PRONEX, Brazil); Grant sponsor: Hospital de Clınicas de Porto Alegre Key conclusions of the study authors: no significant association was detected between polymorphisms of dopaminergic (DRD4, DAT1) and serotonergic genes (HTR1B, HTR2A, and 5‐HTT) on the response nor side effects to the treatment with methylphenidate Exclusion of methylphenidate non‐responders/children who have previously experienced adverse events on methylphenidate: no, 100% were methylphenidate‐naïve Supplemental information received through personal email correspondence with the authors in September 2016 (Zeni 2016 [pers comm])