Attention Deficit Hyperactivity Disorder (ADHD) and its Comorbid Mental Disorders: An Evaluation of their Labor Market Outcomes.

Background: Attention-deficit/hyper-activity disorder's (ADHD) prevalence rate has been increasing during the last decade. Evidence from different studies suggests that the effect of ADHD on earnings and employment could be more detrimental than other disorders such as depression or anxiety. Although it is widely known that these mental disorders can coexist with ADHD, none of these studies has considered the joint evaluation of ADHD and its comorbidities.

Objective: In this paper, we evaluate whether ADHD is a more severe disorder than three other comorbid mental disorders -- learning disabilities, depression, and anxiety -- regarding their effects on earnings and employment.

Methods: We use the National Longitudinal Study of Adolescent to Adult Health to estimate regression models of earnings and employment. We consider the use of the sampling weights, school fixed effects, and multiple imputation of missing values. Robustness checks include a more exogenous measure of depression.

Results: On average, an individual with ADHD or depression (but not both) has around 20% lower earnings than those without any of these disorders. The earnings gap for learning disabilities is around 25%. The probability of being employed is 5 percentage points lower for an individual who has any of these disorders. Anxiety is not associated with lower earnings. Females with learning disabilities have an earnings gap that is 20 percentage points larger than males. The employment gap for females or African Americans with learning disabilities is 8%.

Discussion and limitations: In contrast to existing evidence, we find that ADHD is not more serious than learning disabilities or depression. Although the magnitude of each employment gap is not substantial, the fact that these are comorbid disorders indicates that their joint occurrence could be detrimental for employment. Females and African Americans with learning disabilities could face more adverse labor market outcomes. Even though our results are robust to a more exogenous measure of depression, the potential endogeneity of the diagnosis of ADHD or anxiety could still bias the estimates. However, baseline results are also robust when individuals with an age of diagnosis equal to the year of the interview are dropped from the estimations.

Implications for health policy and for future research: The increasing number of Supplemental Security Income beneficiaries with ADHD is in line with the observed tendency to screen for ADHD more frequently than for other comorbid disorders, and with the evidence of ADHD overdiagnosis. Since our study shows that other disorders are equally or potentially more disabling than ADHD in terms of labor market outcomes, mental health policies should be reoriented to prevent policies targeting ADHD from crowding out those for other mental disorders. It would be interesting to verify our findings using a more recent cohort with a higher rate of ADHD diagnosis. Since we show that there are unexplained gender and race differences that persist after controlling for educational attainment or the number of hours worked, more research is needed to determine the reason behind these differences. Further research about the positive school effect on the adulthood performance of ADHD children is needed.