Understanding your personal health and your family's health history is another important part of the diagnosis, especially if your symptoms came on recently — a strong indication you are suffering from a condition other than adult ADHD. Your doctor may administer or prescribe a psychiatric and medical exam to look for diseases and conditions that may impact your ability to pay attention and focus, or which may cause you to feel and act hyperactive and impulsive. These may include learning disabilities, hyperthyroidism, hypothyroidism, fetal alcohol syndrome, depression, and anxiety.

Other Childhood Illness That May Have an Impact on ADHD

Your medical expert will also probably review your childhood medical records for evidence of diseases and conditions that are often linked with ADHD.

• Vision and hearing problems may also cause or masquerade as ADHD in childhood. Recent studies show that children with convergence insufficiency, a physical eye problem that makes it hard to keep both eyes pointed and focused at a near target, are three times as likely to be diagnosed with ADHD than children without the disorder.

• Central Auditory Processing Disorder (CAPD) will sometimes occur in children who have had a history of ear infections and/or PE tubes. Symptoms include distractibility, inability to follow a set of verbal instructions, and spacing out.

• Yeast infections cause hyperactivity in children. Most children who suffer from yeast infections have some underlying problem that is frequently traced to an immune disorder or a disorder affecting carbohydrate metabolism that alters blood sugar levels. In yeast infections, intestinal parasites rob the body of needed nutrients, which in turn affects behavior.

• Streptococcus bacteria, better known as strep, can cause rheumatic fever and a movement disorder known as Sydenham's chorea if left untreated. Recurrent infections can also lead to a group of symptoms collectively known as PANDAS (pediatric autoimmune neuropsychiatric disorders). Some symptoms of PANDAS include obsessive-compulsive behavior, Tourette's syndrome, hyperactivity, cognitive problems, and fidgeting.

• Hypoglycemia, or low blood sugar, can stem from thyroid disorders, liver or pancreatic problems, adrenal gland abnormalities, or insufficient diet.

• Head injuries such as post-concussion syndrome have symptoms that include irritability, mood swings, memory problems, depression, and sleeping problems.

• Some spinal problems can cause ADHD-like behavior. If the spine is not connected to the brain properly, nerves from the spinal cord can give the brain all of the signals at once and cause a child to be hyperactive.

• Some drugs can cause the brain to atrophy, leading to disturbed cognition and behavior. If a child routinely takes prescription or over-the-counter medications for asthma, hay fever, allergies, headaches, or any other condition, medication may cause or contribute to behavior problems.

• Sniffing materials such as modeling glue or other household products can cause hyperactivity and inattention.

Your physician will gather information on your personal and family medical history, including records of allergies, asthma, tics, epilepsy, or other medical conditions, and a history of your major developmental milestones, such as when you first crawled, walked, spoke, and read. He will also inquire about psychiatric disease, depression, alcoholism, and substance abuse in your family history.

Coexisting Conditions That Mimic ADHD

Most children and adults with ADHD also suffer from a variety of comorbid conditions. Brain scans, such as EEG, CT, or MRI, may be done to rule out brain abnormalities that are not consistent with ADHD, and a variety of tests may be given to test IQ and memory and detect learning disabilities and cognitive defects.

Finding Patterns in Childhood Tests

While no single medical, neurological, or attention test reliably identifies ADHD, sometimes doctors can identify patterns across several different tests that point to the presence of the condition.

While the particular combination of tests you take will be determined by your doctor, they will probably include measurements of personality and problem solving styles, current fears and concerns, and intellectual functioning. You may also be asked to take a self-report test in which you answer a series of questions about your symptoms, thoughts, and feelings. Your doctor may also ask a spouse, parent, or close friend to fill out a behavior checklist that describes various behaviors associated with ADHD.