How common is it to have ADHD and bipolar disorder (BD) together?

In 2016, the National Survey of Children’s Health (NSCH) found that an estimated 6.1 million children between the ages of 2 and 17 were diagnosed with and treated for ADHD (Danielson et al., 2018). Up to 20% of patient’s meeting criteria for BD also meet the criteria for ADHD; however, treatment for both disorders are very different. Due to the presentation of both disorders, which includes irritability, poor impulse control, mood symptoms and restlessness, both disorders are under diagnosed, misdiagnosed or over diagnosed.