TABLE 1.

Chronic pain and cognitive function

Study	Sample	Variables and measures	Main outcomes
Zohsel et al, 2008 (15), significant study	n=30 children (with migraine, n=15; controls, n=15) Sex: 15 girls (7 with migraine; 8 controls) Age range: 10–15 years	ERPs: Somatosensory N150 amplitude and latency, somatosensory P260 amplitude and latency, somatosensory P300 amplitude and latency, auditory P300 amplitude and latency; VAS (rating perceived stimulus intensity)	Significant association. In response to painful and nonpainful stimuli, children with migraines showed larger somatosensory P300 amplitudes (group: F[1, 28]=6.90, P<0.05; group × intensity: P>0.2) and shorter somatosensory P300 latency (group: F[1, 28]=15.54, P<0.011; group × intensity: P>0.8)
Logan et al, 2008 (24), significant study	n=220 adolescents with chronic pain Sex: 79.8% females Mean age (range): 14.7 years (12–17 years)	Pain/school attendance/academic performance (VAS). Academic competence: Self-Perception Profile for Adolescents, Walker-McConnell Scale of Social Competence and School Adjustment	Significant association. Decreased academic performance: 44.3% of parents reported a decline in their adolescent’s grades since the onset of pain. Chronic pain and school attendance: 44% of students with chronic pain missed at least 25% of school days, and 20% missed more than one-half of school days; adolescents with neuropathic pain had significantly better school attendance than participants with nonmigraine headaches (mean [± SD] difference 0.19±0.07, P<0.05) or functional abdominal pain (mean difference 0.27±0.09, P<0.05)
Ho et al, 2008 (19), significant study	n=57 children with chronic pain Sex: 46 females Mean age (range): 14.64 years (8–18 years)	Cognitive ability: WISC-III and WISC-IV, Wechsler Adult Intelligence Scale III. Academic achievement: WRAT-3, GORT-3, GORT-4, Test of Written Language 3, Wechsler Individual Achievement Test II	Significant association. Cognitive functioning compared with the general population: Chronic pain participants showed higher mean scores in general intelligence (z=4.95, P<0.000001), verbal intelligence (z=5.18, P<0.000001), performance intelligence (z=3.49, P<0.0005), verbal comprehension (z=6.16, P<0.000001), perceptual organization (z=4.18, P<0.00005) and processing speed (z=2.82, P<0.005). No significant differences were seen in working memory (z=0.92). Academic achievement scores compared with the general population: Chronic pain participants showed higher mean scores in word reading (z=4.31, P<0.00005) and mathematical reasoning (z=2.70, P<0.01). No significant differences were seen in reading comprehension (z=1.82), arithmetic computation (z=0.05), spelling (z=2.27) or written expression (z=2.51)
Buodo et al, 2004 (16), significant study	n=36 children (with migraine, n=18; controls, n=18) Sex: 17 females (10 with migraine; 7 controls) Mean age (range): With migraine, 10.6±2.1 years (8–14 years); controls, 10.7±2 years (8–14 years)	Electroencephalogram recorded from three sites: Fz, Cz and Pz. ERPs: N100 amplitude and latency (target and standard stimulus type), and P300 amplitude and latency (target and standard stimulus type). Reaction times: Acoustic oddball paradigm	Significant association. Group differences: Smaller N100 amplitude to standard stimuli in children with migraines; significant amplitude difference between standard and target N100 in children with migraines; target P300 amplitude habituated in children with migraines, but not in control subjects. Group-stimulus interaction (F[1, 34]=3.18, P<0.08): P300 latency for frequent stimuli longer in children with migraines; significant positive correlation between reaction times and target P300 latency in children with migraines
Boyer et al, 2006 (25), significant study	n=59 children with recurrent abdominal pain Sex: 33 girls Mean age (range): 12.59 years (9–17 years)	Dot-probe task; Abdominal Pain Index; Body Vigilance Scale; Child Behavior Checklist	Significant association. Attentional bias: A three-way interaction found for threat word position, dot probe position and exposure position (F[1, 56]=4.44, P<0.05). Within subliminal condition, participants responded faster when dot probes replaced the threat word of the threat-neutral word pairs and responded slower when dot probes replaced the neutral word of the threat-neutral word pairs. Reversed pattern appeared in supraliminal condition (participants avoiding threat words in this condition). Biases toward supraliminally presented social threat words negatively correlated with both biases toward subliminally presented pain words (r=−0.30, P<0.05) and attentional biases toward subliminally presented social threat words (r=−0.29, P<0.05). Biases to attend to supraliminally presented pain words were negatively associated with parents’ reports of child’s abdominal pain (r=−0.31, P<0.05) but positively correlated with parents’ reports of children’s anxiety/depression (r=0.36, P<0.05). Biases to attend to subliminally presented social threat words positively correlated with children’s reports of body vigilance (r=0.32, P<0.05) and abdominal pain (r=0.35, P<0.05), and marginally correlated with parent-reported somatic complaints (r=0.28, P<0.10)
Koutantji et al, 1999 (26), significant study	n=36 children (children with musculoskeletal pain, n=18; control group, n=18) Sex: 24 females (13 with musculoskeletal pain; 11 controls) Age range: 10.5–16 years (mean age for children with musculoskeletal pain = 13.42 years; mean age for control group = 13.28 years)	VAS (rating various aspects of pain experience); McGill Pain Questionnaire; processing memory task (2 recall lists)	Significant association. Recall scores: Difference on recall between groups only for words encoded in the self-reference condition (F[1, 34]=3.75, exact P=0.061); pain group (mean 0.31±0.14) recalling more information encoded in the self-reference condition than control group (mean 0.23±0.12); significant effect of reference condition for pain group on recall of sensory words (F[1, 34]=6.71, P<0.05) but not for control group; sensory words in self-reference condition in pain group better recalled than other reference encoding (self-reference mean 0.42±0.19, other reference mean 0.26±0.20); significant differences between groups for reference condition on recall of neutral (F[1, 34]=4.19, P<0.05) and sensory words (F[1, 34]=8.46, P<0.05), but not for affective words (F[1, 34]<1); main effect of word type significant (F[2, 68]=3.63, P<0.05); significant difference in recall of sensory words compared with recall of affective words with increased recall of sensory words (F[1, 34]=3.63, P<0.05) (neutral words, mean 0.24±0.14; sensory words, mean 0.31±0.13; affective words, mean 0.25±0.14). Processing time: Significant interaction by word type (F[2, 68]=3.93, P<0.05); group by reference interaction for sensory words (F[1, 34]=3.65, exact P=0.064); pain group spent less time processing sensory information in self-reference condition than control group (F[1, 35]=3.60, exact P=0.066)
Sherry et al, 1991 (17), significant study	n=100 children with musculoskeletal pain Sex: 76 females Age range: 3–20 years	WISC – Revised; WRAT – Revised; Woodcock-Johnson Psychoeducational Battery; VAS (mothers rated patient’s overall state of health)	Significant association. Of the 62 children tested, all were found to have full-scale IQ scores in the average range. Seven children with IQ scores in the average range were reported to have low school achievements tests. No data were provided regarding the extent of those deficits
Haverkamp et al, 2002 (18), significant study	n=54 children (with migraines, n=37; healthy siblings, n=17) Sex: 26 females (15 with migraines; 11 healthy siblings) Mean age: With migraines, 10±2.10 years; healthy siblings, 8.81±2.61 years	Kaufman-Assessment Battery for Children, which includes two cognitive scales: SEQ and SIM. Results of both scales summarized to total scale of mental performance composite	Significant association. Memory: Children with migraines performed relatively worse in test items requiring memory abilities (as assessed by the SEQ). Significant difference between SEQ and SIM only in children without siblings and control group. No differences in children with migraines simultaneously having a sibling
Bell et al, 1994 (20), non-significant study	n=8 with fibromyalgia syndrome (group I) Sex: 8 girls Mean age: 12.45 years	VAS (rating 12 common symptoms)	Cognitive dysfunction 6.75/10; muscle pain 8.5/10

ERP Event-related brain potential; GORT Gray Oral Reading Test; IQ Intelligence quotient; SEQ Sequential information processing; SIM Simultaneous information processing; VAS Visual analogue scale; WISC Wechsler Intelligence Scale for Children; WRAT Wide Range Achievement Test