ADHD is a syndrome characterized by a collection of common symptoms, any one of which can be mimicked by numerous other problems. This is why making a careful diagnosis is so essential. The ADHD specialist, as part of this diagnosis, will consider all other possible causes of the clinical picture and will take a history, do an examination, and sometimes give tests to rule out these other causes. The most common include the following.Mental retardation.Borderline low intelligence. When these children are placed in academic settings beyond their intellectual ability, they frequently show symptoms of inattention and hyperactivity.Intellectually gifted children. If these children are placed in an academically understimulating environment, they may be bored, fidgety, and inattentive and may even exhibit behavior problems.Learning disabilities. There are several different kinds of learning disabilities that may occur in children of normal and superior intelligence and that can be diagnosed by neuropsychological testing. If not treated, these can result in academic underachievement, frustration, and low self-esteem and secondary inattention and behavior problems. It is essential that learning disabilities be ruled out as a cause of academic and behavioral difficulties in a hyperactive youngster. They may take several forms, including disorders of reading, mathematics, written expression, motor skills, or language.Vision or hearing impairment. If the pediatrician has any suspicion that one of these is present, the child should be examined by a specialist.Pervasive developmental disorder. This disorder includes what used to be called autism. It should be considered when a child with the features of ADHD also has severe language impairment, seems unable to relate to people and has strange, stereotypically autistic behaviors.Family problems. Situations such as divorce, a death in the family, or the loss of a parent’s job can greatly affect the emotional well-being of young children and adolescents, resulting in disruptive behavior, anger, aggression, and low self-esteem. In most cases, the child’s behavior returns to normal once the problem issue has been resolved or the child comes to terms with it. Excessively permissive or extremely punitive parenting, inadequate and chaotic home environments, and parental neglect may result in a clinical picture similar to that of ADHD.Oppositional defiant disorder (ODD). While some children with ADHD may develop ODD, it is possible for this condition to exist on its own. Signs of ODD include impulsive aggressivity, defiance of adults, deliberately annoying or hurting people, blaming others for behavior, and refusing or avoiding academic tasks. Conduct disorder. This diagnosis implies a persistent pattern of aggression toward people and animals, destruction of property, deceitfulness, theft, and serious violations of rules. In children this may include running away from home, drug use, and school truancy. Manic episode. The manic phase of a bipolar illness can resemble ADHD with its agitation, mood lability, restlessness, distractibility, and impulsivity. Usually, a careful history and exam will reveal differences. Depression. Similarly, a severe depression could look like ADHD, just as a person with ADHD may be secondarily quite depressed. It is important for the specialist to try to determine which is the primary condition.Adjustment disorder. An acutely traumatic situation or event can lead to an ADHD-like reaction. However, in this case, symptoms would not have the long history present in attention deficit hyperactivity disorder.Child or adolescent antisocial behavior.Antisocial personality disorder. This diagnosis is reserved for adults with a clinical picture similar to the conduct disorder described above. While antisocial personality disorder should be considered as an alternative diagnosis to adult ADHD, it is, unfortunately, often a coexisting condition.Food allergies. This is much less common than generally believed, but if a child is proven to be allergic to certain foods, then the symptoms of hyperactivity should abate when the food is omitted from the diet.Drug use. It is an unfortunate fact that children as young as elementary school age are already experimenting with marijuana, alcohol, speed, hallucinogens and other illicit drugs, and certain symptoms of ADHD, such as zoning out, irritability, poor attention, and hyperactivity may be the results of such use. No parent wants to believe that his or her child is involved in drugs, but it’s an issue that needs to be addressed if your child’s condition is to be diagnosed and managed.Viral diseases. Following the 1917 encephalitis outbreak, many children had a persistent post-encephalitis syndrome that closely mimicked ADHD. A rare cause like this should certainly be ruled out during the preliminary, thorough medical history and examination.Other medical conditions. Poor medical care, chronic infections, hormonal disorders, anemia, malnutrition, and sleep deprivation can all produce symptoms reminiscent of ADHD, and need to be ruled out during the preliminary health checkup.Temperament. Some children are just naturally energetic and rambunctious. Temperament is determined by a great many factors, including genetics, parenting, and environment, and can change dramatically from one developmental stage to another. A child who is colicky in infancy, for example, may grow up to be quiet and peaceful, while another who is calm in infancy may grow up to be hyperactive and difficult to manage. With this in mind, it’s important to remember that a child’s temperament is not always a predictor of ADHD. Other factors must also be taken into consideration.Hunger. It’s frightening to think that there are children in this country who go to bed hungry every night, but it does occur and in far greater numbers than many people realize. Sadly, many of these children may be exhibiting symptoms of ADHD. Poor nutrition can have a tremendous impact on a child’s ability to think, learn, and behave. Fatigue can have a similar impact.School difficulties. A poor student-teacher relationship, problems with friends or classmates, and other related classroom difficulties external to the child may cause otherwise healthy and normal youngsters to behave in ways that mimic ADHD. In the majority of cases, when these problems are properly addressed and students are placed in a class that’s on their level, behavior returns to normal.*12\173\2*