Two new studies led by researchers at McMaster University and St. Joseph's Healthcare Hamilton have found that individuals diagnosed with ADHD or obesity are more likely to choose smaller immediate rewards over larger future rewards.

This reduced capacity to delay gratification in many individuals diagnosed with ADHD or obesity may lead to new approaches for the clinical treatment of these conditions.

The studies, led by Drs. James MacKillop and Michael Amlung of the Peter Boris Centre for Addictions Research at McMaster University and St. Joseph's Healthcare Hamilton, have been published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging and Psychological Medicine.

The findings from these new studies parallel a 2011 study conducted by the authors that found that the ability to delay gratification was reduced in individuals diagnosed with addictive disorders.

"In the context of addictions, there is an increasing appreciation that we need to improve treatment that we provide for patients who substantially devalue future rewards," said MacKillop. "These studies suggest that a simple assessment that measures this phenomenon may also help clinicians to better understand some of their patients that have been diagnosed with ADHD and obesity."

The studies were meta-analyses, or studies that combine the findings across many previous investigations to detect consistent or inconsistent patterns of findings. In the case of the ADHD study, the meta-analysis combined the findings from 21 previous studies including almost 4,000 participants. In the case of the obesity study, the meta-analysis combined the findings from almost 39 studies including over 10,000 participants.

Although the results of prior research appeared to be mixed, these new studies found a highly consistent reduction in capacity to delay gratification in relation to both clinical conditions.

"While not all individuals diagnosed with ADHD and obesity display this pattern of reduced capacity to delay gratification, the connection between this phenomenon and addictions as well as these clinical conditions is clear," said Amlung.

"In the context of obesity specifically, these findings may help inform clinical approaches to weight management that increase individuals' focus toward the longer-term rewards of weight loss."

A second important finding in both studies was that, although the methods varied considerably across the previous studies, reanalyzing the data based on different methods did not appreciably alter the overall findings.

"These studies suggest that, despite different experimental tasks, ages and study designs, immediate reward orientation is robustly elevated in both ADHD and obesity," said Dr. MacKillop.

The studies were funded in part by grants from the National Institutes of Health and the Peter Boris Centre for Addictions Research.