The attention deficit hyperactivity disorder phenotype as a summation of deficits in executive functioning and reward sensitivity: does this explain its relationship with oppositional defiant disorder?

OBJECTIVE: Attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD) commonly coexist but the relationship between them has not been well explained. We present a view of the ADHD phenotype as a summation of deficits in executive functioning and reward sensitivity and apply this to explain its co-occurrence with ODD. MODEL: ADHD relates to difficulty in sustaining concentration for completing tasks. This is associated with lack of reward due to lack of achievement. The unfavorable balance of effort to reward in ADHD is exacerbated in ODD, a condition in which lack of reward is responsible for an adverse effect on mood resulting in a negative attitude and oppositional behavior. We have called this model the "Mental effort-reward imbalances model".
CONCLUSION: This model predicts that oppositional symptoms would be highly prevalent in ADHD, to the extent that ODD would be a frequent co-morbidity.