In the mid-1970s, ADHD was finally classified as an official disorder. Studies around this time showed the condition appeared to be highly genetic. Many parents of children with ADHD also suffered from the telltale signs of ADHD, including inattention, impulsivity, and hyperactivity. But the adults were manifesting their ADHD symptoms differently.

Today, scientists agree that ADHD is a biological disorder of the nervous system that begins in children and often continues into adulthood. While the jury is still out on the exact cause of the condition, studies increasingly point to a chemical imbalance in three of the brain's key neurotransmitters — dopamine, norepinephrine, and serotonin.

How ADD Became ADHD

To cover their bases, psychiatrists decided in 1980 to reclassify ADHD as two separate subsets. One was attention deficit disorder with hyperactivity, or ADD — H. The other was attention deficit disorder without hyperactivity, or ADD no H. On further study, researchers realized hyperactivity/impulsivity was actually a larger problem than inattention, and decided to change the name of the disorder to reflect their findings.

In 1987, the disorder was renamed attention deficit hyperactivity disorder, or ADHD, and reclassified as a disorder with not two, but three distinct subsets: inattentive, hyperactive/impulsive, and combination (people who display both inattentive and hyperactive/impulsive symptoms). For the purpose of this book, the disorder will be called adult ADHD to comply with current psychiatric terminology.