Effects of methylphenidate on discounting of delayed rewards in attention deficit/hyperactivity disorder.

Abstract

Impulsivity is a central component of attention-deficit/hyperactivity disorder (ADHD). Delay discounting, or a preference for smaller, immediate rewards over larger, delayed rewards is considered an important aspect of impulsivity, and delay-related impulsivity has been emphasized in etiological models of ADHD. The current study examined whether stimulant medication, an effective treatment for ADHD, reduces discounting of delayed experiential and hypothetical rewards among 49 children (age 9-12 years) with ADHD. Following a practice day, participants completed a 3-day double-blind placebo-controlled acute medication assessment. Active doses were long-acting methylphenidate (Concerta), with the nearest equivalents of 0.3 and 0.6 mg/kg TID immediate-release methylphenidate. On each testing day, participants completed experiential (real-world money in real time) and hypothetical discounting tasks. Relative to placebo, methylphenidate reduced discounting of delayed experiential rewards, but not hypothetical rewards. Broadly consistent with etiological models that emphasize delay-related impulsivity among children with ADHD, these findings provide initial evidence that stimulant medication reduces delay discounting among those with the disorder. The present results also draw attention to task parameters that may influence the sensitivity of various delay discounting measures to medication effects.Attention-deficit/hyperactivity disorder (ADHD) is a heterogeneous disorder characterized by developmentally inappropriate and impairing levels of inattention and/or hyperactivity and impulsivity (see American Psychiatric Association, 2000;Swanson et al., 1998). Etiological models of ADHD implicate cognitive and motivational processes, and an integration of these processes as in the dual-pathway model of ADHD (Sonuga-Barke, 2002, 2005. Within this model, impulsive behavior is characterized in part as a rational choice to avoid delay because it is experienced as aversive. Delay aversion is considered an important pathway in the development of ADHD, along with executive function deficits such as inhibitory control . The delay aversion hypothesis emphasizes the negative motivational and emotional significance of delay for children with ADHD as an expression of a broader motivational style, which results in a preference for immediate over delayed rewards (Sonuga-Barke, Sergeant, Nigg, & Willcutt,

Functional Genetic Variation in Dopamine Signaling Moderates Prefrontal Cortical Activity During Risky Decision Making

“…A growing literature suggests that dopaminergic abnormalities underlie impairments in decision making, which accompany a number of neuropsychiatric disorders (Rahman et al, 2001), but the effects of dopaminergic drugs on risk-taking behavior are inconsistent. For example, administration of dopamine agonists promotes risky choices in Parkinson's disease (Cools and D'Esposito, 2011) and in healthy controls (Riba et al, 2008), but reduces risk-taking behaviors (DeVito et al, 2008) and impulsive decisions (Shiels et al, 2009) in children with attention deficit hyperactivity disorder. Although the effects of amphetamine and haloperidol are not limited to dopaminergic systems, the administration of either drug, despite the opposite effects on dopamine signaling increases motivation to gamble in problem gamblers Poulos, 2004, 2007), suggesting that the link between dopamine signaling and risk-taking behavior is not simply a linear relationship.…”

The Roles of Dopamine and Serotonin in Decision Making: Evidence from Pharmacological Experiments in Humans

“…Experimental evidence has also shown that administration of amphetamine and the D 2 receptor antagonist, haloperidol, can prime cognitions that promote gambling behavior as well as enhance its reinforcement value in samples of individuals with gambling problems (Zack and Poulos, 2004). Finally, the mixed dopamine and noradrenaline agent, methylphenidate, has also been shown to ameliorate the risk-taking behavior of children with diagnosis of DSM-IV attention-deficit-hyperactivity disorder (ADHD) when asked to place 'bets' on their previous decisions being correct (DeVito et al, 2008), as well as reducing the number of impulsive decisions in the performance of delay-discounting tasks (Shiels et al, 2009). Dopaminergic agents also appear to improve decision making in adult clinical populations.…”

Connectivity Strength of Dissociable Striatal Tracts Predict Individual Differences in Temporal Discounting

“…Understanding individual differences in how people trade off reward magnitude and delay (i.e., delay discounting) is of high ecological and clinical relevance. Rates of delay discounting predict important outcomes in education, health, and savings and are abnormal in a range of psychiatric conditions, including addiction and attention-deficit hyperactivity disorder (Madden et al, 1997;Vuchinich and Simpson, 1998;Kirby and Petry, 1999;Mitchell, 1999;Marco et al, 2009;Shiels et al, 2009).…”