Do one in 20 Australians need amphetamines?

Key points:

• New research has revealed that people with attention-deficit/hyperactivity disorder have lower motivation to invest effort in both cognitive and physical tasks

• Amphetamine use increased motivation for cognitive and physical tasks in individuals with ADHD in a recent trial

• One in 20 Australians lives with ADHD

In a world-first study, Monash University researchers have found that the hallmark ‘lower motivation’ observed in people with ADHD is actually an avoidance of effort, both mental and physical.

The study found that through the use of prescription amphetamines, people with ADHD were able to demonstrate similar levels of motivation and effort in physical and cognitive tasks to people without the condition.

The research team, led by Associate Professor Trevor Chong, from the Turner Institute for Brain and Mental Health and Monash School of Psychological Sciences, is the first to study people with ADHD’s sensitivity to effort and how medication can amend that.

“Until now, no study has explicitly tested the proposition that ADHD is associated with lower motivation to invest cognitive effort and very few have examined the motivation to invest physical effort in this population,” he said.

“Our study provides the first evidence that cognitive motivation is indeed lower in individuals with ADHD than those without and that this is also accompanied by a lower willingness to invest physical effort.

 

“Our data reassuringly shows that medications that are commonly used to treat ADHD are effective in improving motivation to [a] level similar to those who do not have the condition.”

The researchers tested 24 control participants and 20 individuals with ADHD — 11 males, 9 females — who were managed with amphetamine-based medications: dexamphetamine and its prodrug, lisdexamphetamine.

Currently, all States and Territories have different laws about Schedule 8 prescribed stimulants. Some drugs commonly prescribed in the United States of America, such as Adderall, are illicit in Australia.

The participants with ADHD were tested when they were off-medication and when they were on their medication, in an effort-based decision-making task. Participants revealed their preference between a fixed, low-effort/low-reward baseline option and a variable, high-effort/high-reward offer.

Participants were also required to monitor a series of rapidly changing letters and press a button whenever they detected the target letter — ‘T’ — as part of an increasingly difficult cognitive task.

In the physical effort task, participants exerted one of six levels of force on a hand-held dynamometer and had to maintain their contraction to receive a reward. 

The results revealed three main findings:

• Individuals with ADHD had lower motivation to invest effort in both the cognitive and physical domains
• Amphetamine increased motivation uniformly across both domains
• The net effect of amphetamine treatment was to mostly restore motivation across both domains of effort relative to healthy controls

The 37-page research study, published in the Journal of Neuroscience, concluded:

“This provides further confirmatory evidence that the motivational deficits in ADHD are not secondary to dysfunction of particular cognitive domains; rather, it is likely to represent a primary dysfunction in these individuals.”

Do you live with ADHD? Let the team at Talking Disability know your experiences with motivation, medication and more!