Table 2.

Task measures at baseline and 7 weeks in children and adolescents treated with methylphenidate for >2 years, comparing a discontinuation group (withdrawal to placebo) and a continuation group (continued methylphenidate use)

Measure	Discontinuation group n = 47				delta a	Continuation group n = 47				delta a	Δ Change between groups b	95% CI	Cohen’s f2
	Baseline		7 weeks			Baseline		7 weeks
	Mean	SD	Mean	SD		Mean	SD	Mean	SD
Working memory
RT	386	272	422	287	35.8	378	267	535	319.83	157	121	38.9, 203
ER	1.02	2.06	2.28	2.07	1.26	1.81	1.79	1.44	1.65	−0.37	1.63*	1.09, 2.17	.14
Response inhibition
RT	195	121	127	103	−68.2	186	132	154	124.26	−32.3	35.9	−66.7, 2.15
ER	1.50	2.10	1.12	1.54	−0.38	0.67	1.98	0.70	1.22	0.03	0.41	−0.09, 0.91
Attentional flexibility
RT	542	249	395	237	−146	542	255	383	162.28	−159	13.0	−52.4, 78.4
ER	3.26	3.15	2.81	3.10	−0.45	2.70	2.96	2.31	2.81	−0.39	0.06	−0.80, 0.92
Psychomotor speed
RT	320	49.7	328	41.2	8.10	322	41.0	332	40.35	10.4	2.27	−10.1, 14.6

RT, reaction time in milliseconds; ER, error rate; working memory by the Memory Search Letters task; response inhibition and attentional flexibility by the Shifting Attentional Set—Visual (SSV) task, and psychomotor speed by the Baseline Speed task (De Sonneville, 1999).

^a The difference between seven weeks and baseline.

^b The difference in mean change from baseline to seven weeks between the discontinuation and continuation group, by mixed models analyses.

^* p < .0074 using Bonferroni correction for multiple testing.