DELAY AVERSION IN ADHD: A LARGE SCALE ASSESSMENT DELAY AVERSION IN ADHD: A LARGE SCALE ASSESSMENT OF THE IMPACT OF PRE- AND POST-REWARDED DELAY OF THE IMPACT OF PRE- AND POST-REWARDED DELAY

ON CHOICE BEHAVIOURON CHOICE BEHAVIOUR

Marco R1, Schlotz W2, Melia A1, Sonuga-Barke EJS2, Mulligan A3, Mueller U4, Kuntsi J5,

Uebel H6, Andreou P5, Meidad S9, Manor I9, Gabriels I8, Rothenberger A6, Christiansen H7, Asherson P5, Gill M3, Steinhausen HC4, Banaschewski T6, Roeyers

H8, Oades RD7, Miranda A1

BACKGROUND

The finding that executive dysfunction is present within only a subgroup of patients (Nigg et al., 2005) has led to a renewed interest in the role of motivational dysfunction in Attention Deficit/Hyperactivity Disorder (Castellanos et al., 2006).

At present there is no consistent and compelling evidence for most of the many motivational hypotheses for ADHD (Luman et al., 2004).

The hypothesis that ADHD children appear unusually sensitive to delayed rewards (Sagvolden et al., 2005) as expressed in their choice for small immediate over delayed rewards may be an exception to this rule.

According to the delay aversion framework (Sonuga-Barke, 2007) ADHD children's preference for small sooner over larger later rewards expresses a more generalised sensitivity to delay which is grounded in brain reward circuits, driven by impaired signalling of future rewards, compounded by delay-related negative affect, and expressed in different ways in different settings.

Choices of small immediate rewards suggest two processes (i) an unconditional preference for immediacy linked to deficits in signalling future rewards and (ii) the desire to escape or avoid the negative delay-related affect. These effects add to cause preference for immediacy over delay.

In the current poster we report a study of these additive effects by examining choice for small immediate and large delayed rewards under two conditions. In one condition there was a post reward delay that equalised the length of trials - i.e., there was no opportunity to reduce trial and so escape delay per se. In the second, the post-reward delay was removed so choice of the small immediate reward led to shorter trials and overall task delay could be avoided by choosing the immediate reward on each trial.

CONCLUSION

ADHD children chose small immediate rewards over large delayed rewards more than controls irrespective of condition.

This effect was exacerbated under the no-post reward delay condition.

The data support a two-process model of ADHD children's preference for small immediate rewards. In the no-post reward delay condition the unconditional preference for immediacy linked to deficits in signalling future rewards is compounded by the motivation to escape or avoid the negative delay-related affect.

Delay aversion is a useful framework for understanding ADHD children choice behaviour.

Future research should use tasks that counteract the ceiling effects seen in the current study especially in the older children.

KEY REFERENCESCastellanos FX, Sonuga-Barke EJS, Milham MP, Tannock R (2006). Characterizing cognition in ADHD: beyond executive dysfunction. Trends In Cog Sci 10: 117-123.Kuntsi J, Oosterlaan J, Stevenson J (2001). Psychological mechanisms in hyperactivity: I response inhibition deficit, working memory impairment, delay aversion, or something else? J Child Psychol Psychiat 42: 199-210. Luman M, Oosterlaan J, Sergeant JA (2005). The impact of reinforcement contingencies on AD/HD: A review and theoretical appraisal. Clin Psychol Rev 25: 183-213. Sagvolden T, Johansen EB, Aase H, Russell VA (2005). A dynamic developmental theory of attention-deficit/hyperactivity disorder (ADHD) predominantly hyperactive/impulsive and combined subtypes. Behav Brain Sciences 28: 397-+.Sonuga-Barke E J S. What role, if any, should markers of motivational disfunction play in the diagnosis of attention deficit hyperactivity disorder? First submission.Brookes K, Xu X, Chen W. et al (2006). The analysis of 51 genes in DSM-IV combined type ADHD: Association signals in DRD4, DAT1 and 16 other genes. Mol Psychiatr; 11: 934-953.Taylor E, Sandberg S, Thorley G, Giles S (1991). The epidemiology of childhood hyper activity. Maudsley Monograph, 33, New York: Oxford University Press.

PREDICTIONS

1) That in general children, irrespective of their ADHD status, would choose the small immediate reward over the large delayed reward more in the no post-reward delay condition where they could reduce trial length. There would be a main effect of condition.

2) ADHD children would show a preference for immediacy and choose the small immediate reward more than controls irrespective of condition expressing their unconditional sensitivity to pre-reward delay. There would be a main effect of group.

3) That the removal of the post-reward delay would increase the preference for the immediate reward more for ADHD than controls as they try to escape the negative affect associated with delay. There would be an interaction between group and condition.

4) This pattern would not be affected by factors such as age and gender.

RESULTS

ADHD children chose the small immediate reward over the large delayed reward more than controls under both conditions (Figure 2).

Figure 3: mean levels (± SEM) of "percent choice of large reward" in the two experimental conditions by age.

Figure 2: mean levels ( SEM) of “percent choice of large reward” in the two experimental conditions.

Prediction 1: Children in general chose the small immediate reward in the no post condition more than in the post condition (Wilcoxon signed-rank test: Z = 10.025; P < 0.0001).

Prediction 2: ADHD children chose the small immediate reward more than controls irrespective of condition (Mann-Whitney test: Z = 7.367; P < 0.0001).

Prediction 3: Increase in rate of small reward choices when condition changed from "post-reward delay" to "no post-reward delay" was higher in ADHD than in controls (Mann-Whitney test: Z = -3.190; P = 0.0014).

Prediction 4: There was no effect of gender but there were effects of age. When the above analyses were performed for children above and below 12 years the main effects of condition and group were present at both ages while the interaction was significant in the younger age group only (Figure 3: < 12 years of age (P = 0.002); tendency in ³ 12 years group (P = 0.090)).

There was a ceiling effect which was stronger in the Post-Reward Delay condition (62% ceiling) than in the No Post-Reward Delay condition (53% ceiling). Due to non-normal distributions, we chose a non-parametric approach for tests of effects and effect sizes. Analyses using dichotomous outcomes (more or less than 50 percent choice for the large rewards) gave the same pattern of results.

METHODS

Participants: 435 ADHD cases (376 males) between the ages 5 and 17 years of age (8 were inattentive and 15 hyperactive/impulsive subtype) with a research diagnosis using the Parental Account of Childhood Symptoms (Taylor et al., 1991), and 219 controls (137 males), between 6 and 16 years, recruited as part of the IMAGE (Brooks et al., 2006) study took part in the study. ADHD cases tended to be younger (p<0.001) and male (P<0.001).

Task: Children completed Maudsley Index of Delay Aversion (MIDA; Kuntsi et al., 2001; figure 1). This was a game-like presentation of a repeated choice between a small immediate reward (shoot one enemy spaceship after 2 seconds) and a large delayed reward (two enemy spaceships after 30 seconds). In one condition there was no post-reward delay and the next trial began immediately after the choice was made and the trial length was reduced if you chose the immediate reward, and in the second, there was post-reward delay so that trial length was not reduced if you chose the immediate alternative. Each trial completed 20 trials and all were aware of this trial constraint which was emphasized during testing using a visual aid.

Figure 1: A screen shot of the Maudsley Index of Delay Aversion

AFFILIATIONS1 Department of Developmental and Educational Psychology, University of Valencia, Spain2 School of Psychology, University of Southampton, UK3 Department of Psychiatry, Trinity Centre for Health Sciences, St. James's Hospital, Dublin,

Ireland4 Department of Child and Adolescent Psychiatry, University of Zurich, Switzerland5 MRC Social Genetic Developmental and Psychiatry Centre, Institute of Psychiatry, London,

UK 6 Dept. of Child and Adolescent Psychiatry, University of Göttingen, Germany7 University Clinic for Child Psychiatry, Essen, Germany8 Department of Experimental Clinical and Health Psychology, University of Ghent, Belgium9 ADHD Clinic, Geha Mental Health Centre, Petach-Tiqva, Israel

AcknowledgementsThe IMAGE-London cognitive endophenotype research is funded by UK Medical Research Council grant G0300189 to J. Kuntsi