This study estimates the prevalence and correlates of DSM-IV adult ADHD in ten countries across the Americas, Europe, and the Middle East (n=11,422). The prevalence of adult ADHD was found to be 3.4%, with lower rates in lower-income countries (1.9%) compared to higher-income countries (4.2%). Adult ADHD often co-occurs with other DSM-IV disorders and is associated with significant role disability. However, few cases are treated for ADHD, with treatment more commonly given for comorbid disorders. The study used a combination of direct interviews and multiple imputation to estimate prevalence and correlates, assuming cross-national calibration comparability. Adult ADHD was assessed using a retrospective interview, with a clinical reappraisal interview used to calibrate the screen. The assessment was limited to respondents aged 18–44 due to concerns about the accuracy of retrospective recall. Adult ADHD was significantly associated with a wide range of other DSM-IV disorders, with the strongest associations found with mood, anxiety, and substance use disorders. The study also found that adult ADHD was more prevalent among men and among individuals with lower educational levels. However, the prevalence of ADHD was not higher among unemployed individuals. The study found that adult ADHD is associated with significant disability in mobility and cognition, but not in self-care. It is also associated with a high number of days out of role and disability in social functioning. Despite these findings, the study notes that the prevalence estimate may be conservative due to limitations in the diagnostic criteria and the use of imputation methods. The study highlights the importance of further research on adult ADHD, as it is a common and often seriously impairing disorder. The findings suggest that adult ADHD is often co-occurring with other disorders and is associated with significant disability. The study also notes that the use of self-reporting in the assessment of adult ADHD may lead to underestimation of the true prevalence and severity of the disorder.This study estimates the prevalence and correlates of DSM-IV adult ADHD in ten countries across the Americas, Europe, and the Middle East (n=11,422). The prevalence of adult ADHD was found to be 3.4%, with lower rates in lower-income countries (1.9%) compared to higher-income countries (4.2%). Adult ADHD often co-occurs with other DSM-IV disorders and is associated with significant role disability. However, few cases are treated for ADHD, with treatment more commonly given for comorbid disorders. The study used a combination of direct interviews and multiple imputation to estimate prevalence and correlates, assuming cross-national calibration comparability. Adult ADHD was assessed using a retrospective interview, with a clinical reappraisal interview used to calibrate the screen. The assessment was limited to respondents aged 18–44 due to concerns about the accuracy of retrospective recall. Adult ADHD was significantly associated with a wide range of other DSM-IV disorders, with the strongest associations found with mood, anxiety, and substance use disorders. The study also found that adult ADHD was more prevalent among men and among individuals with lower educational levels. However, the prevalence of ADHD was not higher among unemployed individuals. The study found that adult ADHD is associated with significant disability in mobility and cognition, but not in self-care. It is also associated with a high number of days out of role and disability in social functioning. Despite these findings, the study notes that the prevalence estimate may be conservative due to limitations in the diagnostic criteria and the use of imputation methods. The study highlights the importance of further research on adult ADHD, as it is a common and often seriously impairing disorder. The findings suggest that adult ADHD is often co-occurring with other disorders and is associated with significant disability. The study also notes that the use of self-reporting in the assessment of adult ADHD may lead to underestimation of the true prevalence and severity of the disorder.