There are a number of common comorbid, or coexisting conditions, that often accompany ADHD. Anxiety is one of them. According to the Anxiety Disorders Association of America, approximately one half of all adults with ADHD also suffer with an anxiety disorder.  We all feel stress or are nervous at some time but an anxiety disorder significantly impacts your ability to function or carry out daily activities.
What is an Anxiety Disorder?
Anxiety disorders are characterized by excessive and irrational worrying. You may worry about a disaster happening in the future or anticipate future problems even though you have no reason to do so. The fear brought about by anxiety can stop you from participating in events or, in some cases, even leaving the house. There are also a number of physical symptoms that you may experience, such as headaches, stomach aches, difficulty breathing, restlessness, insomnia and problems focusing.
Primary vs. Secondary Anxiety
With such a high percentage of individuals with ADHD also showing signs of anxiety, the question of whether anxiety can be a byproduct of ADHD is frequently asked. Living with ADHD can be stressful. Children with ADHD worry about fitting in with peers and may feel pressure over grades and school performance. They may feel that no matter what they do, they get into trouble. Adults with ADHD often struggle in their jobs and their relationships. All of this adds stress and can contribute to feelings of anxiety. When the symptoms of ADHD cause anxiety, this is considered secondary. In these cases, there is no family history of anxiety and, when the ADHD symptoms are treated and managed, the anxiety disappears.
Primary anxiety is when an anxiety disorder is separate, or exists alongside the ADHD. Because anxiety disorders are often hereditary, there is normally a family history of anxiety disorders. In these cases, you or your child may remember feeling overly anxious throughout your childhood. Managing stress has probably always been difficult.
Determining whether anxiety is primary or secondary is an important part of the diagnostic and treatment process. For example, in secondary anxiety, treating the symptoms of ADHD with medication and behavioral therapy can greatly reduce feelings of anxiety. However, if your anxiety is primary, it will probably need to be treated as a separate disorder.
Complications in Diagnosis
Because anxiety can cause symptoms such as restlessness and the inability to focus, it can sometimes be confused with ADHD, especially in children. Restlessness may be seen as hyperactivity and struggling with focus can be confused with inattention. Qualified mental health professionals should ask questions and probe deeply to find out if excessive worrying or intense feelings of nervousness signify an anxiety disorder. If your doctor is assuming these feelings are a result of failures and frustrations due to ADHD, you may not get any relief from your symptoms.
Stimulant medications, one of the most common ways to treat ADHD, can exacerbate symptoms of anxiety.
Your treatment plan should take into consideration whether your anxiety is primary or secondary. For secondary anxiety, treatment should focus on improving ADHD symptoms while at the same time addressing social and emotional issues to help you or your child develop coping strategies for dealing with stress. If using stimulant medication, you should pay attention to make sure the anxiety symptoms do not worsen. For primary anxiety disorders, your doctor may elect to treat the anxiety first to find out whether symptoms, such as inattention, improve with this treatment.
If symptoms of either ADHD or anxiety continue, or worsen, when one condition is treated, you may need treatment for both.
Besides medication, your doctor may recommend cognitive behavioral therapy, behavioral therapy, stress management training, social skills training and individual or family counseling. Because each person experiences ADHD and anxiety differently, your treatment plan should be tailored to individual needs.
 "Adult ADHD (Attention Deficit/Hyperactivity Disorder),"Date Unknown, Staff Writer, Anxiety Disorders Association of America: http://www.adaa.org/understanding-anxiety/related-illnesses/other-related-conditions/adult-adhd
“Is It Anxiety or ADHD?”, Date Unknown, Larry Silver, M.D., ADDitude Magazine: http://www.additudemag.com/adhd/article/5231.html