Balázs 2011.

Methods	A cohort study of dyskinesia in children routinely using methylphenidate after a single dose of methylphenidate compared to community controls
Participants	Number of participants screened: 94 Number of participants included in the ADHD group: 37 Number of cases followed up: 34 Number of withdrawals: 3 Diagnosis of ADHD: DSM‐IV (subtype: combined (67.6%), hyperactive‐impulsive (10.8%), inattentive (21.6%)) Age: mean 10.8 years, range 7‐17 years old IQ: normal Sex: 32 males, 5 females Methylphenidate‐naïve: 0%. Median prior exposure to methylphenidate: 1074 days Ethnicity: not stated Country: Hungary Comorbidity: not stated Comedication: not stated Sociodemographics: not stated Inclusion criteria Aged 6‐18 years ADHD DSM‐IV diagnosis (using the Mini International Neuropsychiatric Interview Kid 2.0) Receiving methylphenidate Recruited from a child and adolescent psychiatric hospital and outpatient clinic Exclusion criteria: Past or present mental or neurological disorders
Interventions	Methylphenidate type: not stated Methylphenidate dose: not stated Administration schedule: single dose, the same dose which they had been prescribed for their regular treatment Duration of treatment: 1 day Treatment compliance: 3 children left the study after baseline measurements were taken
Outcomes	Non‐serious adverse events: Dyskinesia measured before and 90‐120 minutes after administration of a single dose of methylphenidate by using the Abnormal Involuntary Movement Scale (AIMS) (0 = none, 1 = minimal, 2 = mild, 3 = moderate, 4 = severe)
Notes	Sample calculation: not stated Ethics approval: yes, the study was approved by the Regional Ethics Committee Funding: none reported Vested interest/authors' affiliations: the authors report no conflict of interest Key conclusions of the study authors: methylphenidate‐treated children with ADHD had more dyskinesia than children in the control group. Dyskinesia did not worsen after a single dose of methylphenidate Higher dyskinesia scores in the methylphenidate‐treated younger age group warrant caution in the methylphenidate treatment of ADHD; however, further studies are needed to clarify the possible causal relationship between dyskinesia and methylphenidate treatment and/or age and/or the disease itself Comments from the study authors: we found no relationship between prior methylphenidate exposure of the children with ADHD and the total severity of dyskinesia. We believe that this lack of association is because most of our patients had been receiving long‐term methylphenidate treatment before enrolment in the study. Limitations: no inclusion of treatment‐naïve children with ADHD Comments from the review authors: none of the participants were methylphenidate‐naïve, and the results from the measurements before methylphenidate administration (baseline) are therefore in fact reflecting long‐term use (median prior exposure to methylphenidate: 1074 days). This needs to be taken into account when assessing the results from the measurements after methylphenidate administration in the study (short‐term challenge).