A new study has shown that workers with attention deficit hyperactivity disorder (ADHD) do 22 days less work per year than people without the disorder.
People with ADHD find it difficult to concentrate because they may be hyperactive, easily distracted, forgetful or impulsive, reports BMJ.
Kids who have the disorder are being increasingly diagnosed because they are likely to be tested for ADHD if they have problems with their schoolwork.
However, many adults with ADHD do not know they have the condition.
As part of the World Health Organisation World Mental Health Survey Initiative, more than 7,000 employed and self-employed workers aged 18-44 years were screened for ADHD.
The researchers, who are part of a WHO research consortium at Harvard Medical School, asked the participants about their performance at work in the last month.
On average 3.5 per cent of workers had ADHD. It was more prevalent in men and workers in developed rather than developing countries.
In the study, people who had ADHD were found to spend 22.1 more days not doing work than other workers per year.
This was made up of 8.4 days when they were unable to work or carry out their normal activities, plus 21.7 days of reduced work quantity and 13.6 days of reduced work quality.
The researchers suggest adult ADHD might be a candidate for targeted workplace screening and treatment programmes because cost-effective therapies exist which could improve some aspects of affected workers' performance.
"It might be cost-effective from the employer perspective to implement workplace screening programmes and provide treatment for workers with ADHD," the authors said.
The study is published online ahead of print in Occupational and Environmental Medicine.