In 2005 the Center for Disease Control
published an update of their priority “questions to be answered” on
ADHD, including several relevant to adults in the workplace.

Of note: they specifically  mention a need to assess the economic impact of ADHD in the workplace. 

Below, an
excerpt from ADHD — A Public Health Perspective:

ADHD can be managed through medical and psychosocial interventions.

Recent
research suggests that combining medical and behavioral therapies is an
especially effective approach to treating ADHD and its comorbidities.
However, information on the long-term effects of all treatments is
lacking, as is knowledge of the effects of long-term use of ADHD
medications in children. On-going, systematic monitoring of ADHD,
comorbidities, and treatment modalities is needed.

CDC acknowledges the need for further research in ADHD.  Specifically, key public health questions yet to be answered include:

• What are the causes and risk factors of ADHD?  What is the prevalence of ADHD?  Is the prevalence increasing?

• What social and economic impacts does ADHD have on families; schools; the workforce; and judicial and health systems?

• Are ADHD and its comorbidities being appropriately
  diagnosed and treated? Are people with ADHD able to access appropriate
  and timely treatment?

• How effective are current interventions?  What are the long-term effects of drug treatments?

Full article here at the CDC.