Although you normally think of medication as something that heals or cures a condition, when it comes to adult ADHD some medications produce symptoms that actually mimic the disorder. For instance, that flu medicine you took this morning may have left you feeling nervous, jittery, and irritable, while the sleeping pill you took the night before may have left you feeling confused and lethargic.

Whether it's a seemingly benign over-the-counter pill for a headache, a prescription drug your doctor ordered, or an illegal drug you took because you thought it might help you relax, nearly every drug has side effects that can affect you.

If you think you may have adult ADHD, your doctor will probably ask you to stop taking your medications until he can figure out which symptoms are caused by the medication and which symptoms are caused by the disorder. If you are already addicted to one or more illegal drugs, your doctor may recommend that you undergo detoxification or enter a rehab program before starting treatment for adult ADHD.

Over-the-Counter Drugs

Allergy medications like Claritin and Zyrtec can cause restlessness, nervousness, sleeplessness, excitability, and poor coordination. Diet pills may contain excessive amounts of stimulants like caffeine or green tea that result in nervousness, anxiety, restlessness, an inability to focus, and insomnia.

Sleeping pills can cause confusion, lethargy, and apathy. Cold and flu tablets and syrups that contain antihistamine-decongestant combinations like pseudoephedrine and/or phenylephrine can cause excitability, nervousness, anxiety, and sleeplessness.

Over-the-counter drugs are easy to abuse because they don't require a prescription. To ensure your doctor doesn't confuse the side effects of over-the-counter medications with symptoms of adult ADHD, write down a list of everything you take, including dosage details.

Prescription Drugs

Many prescription drugs also have side effects that can mimic symptoms of adult ADHD. Here is a list of some prescription drugs whose side effects may be mistaken for adult ADHD symptoms.

• Beta blockers: Common side effects include confusion, depression, and memory loss.

• Wellbutrin, prescribed for depression and anxiety as well as smoking cessation: Side effects include nervousness, lightheadedness, excitability, insomnia, nightmares, difficulty concentrating, anger and hostility, depression, and loss of interest.

• Anticonvulsants like Klonopin: Common side effects include poor muscle control and behavioral changes.

• Oral contraceptives: Side effects include depression, nervousness, and tiredness and fatigue.

• Benzodiazepam tranquilizers like Valium and Ativan: Side effects include confusion, depression, lethargy, nervousness, hysteria, and tremors.

• Selective serotonin reuptake inhibitors (SSRIs) prescribed for depression: Common side effects include anxiety, nervousness, sleeplessness, and changes in sex drive.

• Thyroid replacement drugs: Common side effects include nervousness, anxiety, sleeplessness, and heart palpitations.

As with over-the-counter drugs, make a list and give it to your medical doctor so he doesn't confuse side effects for symptoms that may indicate adult ADHD.

Substance Abuse

Unfortunately, many adults with undiagnosed adult ADHD use illegal drugs to mask the symptoms of their disorder. In fact, studies show adult ADHD is associated with an earlier onset of substance abuse, a longer period of active abuse, and a lower rate of recovery.

Adults with ADHD may use a variety of illegal drugs to mask social phobias, nervousness, anxiety, insomnia, an inability to concentrate and focus, and other tell-tale signs of adult ADHD. These drugs include cocaine, marijuana, street amphetamines, street tranquilizers, and the illegal use of stimulant prescription drugs like Ritalin, Adderall, and Concertal.

By the time a patient sees a doctor for adult ADHD, he may already be addicted to a drug that requires a detoxification program. Although stimulant medications like Ritalin and Adderall are commonly prescribed for adult ADHD, they should never be taken without a doctor's supervision or used for off-label purposes like weight loss.