Affective Disorder: A mental disorder characterized by a consistent, pervasive alteration in mood, and affecting thoughts, emotions, and behaviors.

Amphetamines: a racemic compound C9H13N or one of its derivatives (as dextroamphetamine or methamphetamine) frequently abused as a stimulant of the central nervous system but used clinically especially as the sulfate or hydrochloride salt to treat hyperactive children and the symptoms of narcolepsy and as a short-term appetite suppressant in dieting.

Amygdala: An almond-shaped neural structure composed of several nuclei and comprising part of the temporal lobe. It is classified as part of the limbic system and is intimately connected with the hypothalamus, hippocampus, the cingulate gyrus and the septum. It plays a significant role in emotional behavior and motivation, particularly aggressive behaviors, and, as part of the temporal lobe, apparently serves memory functions as well.

Anticonvulsant Medications: A drug that prevents or relieves convulsions or seizures.

Antiobsessional Drugs: A group of drugs used to reduce the symptoms of obsessive-compulsive disorders. Included are clomipramine, fluoxetine and fluvoxamine.

Antipsychotic Drugs: Drugs which help counteract or reverse psychosis, a disturbance in thought processing and behavior leading to a loss of contact with reality.

Asperger's Syndrome or Disorder: A disorder characterized by some of the features of autism such as abnormalities of social interaction and repetitive and stereotyped interests and activities but without the delay or retardation in language and cognitive development that is seen in true autism.

Attachment Disorder: A psychiatric disorder in infants and young children resulting from institutionalization, emotional neglect, or child abuse. Affected children are either withdrawn, aggressive, and fearful or attention-seeking and indiscriminately friendly.

Attention Deficit Disorder: Abbr. ADD. A syndrome, usually diagnosed in childhood, characterized by a persistent pattern of impulsiveness, a short attention span, and often hyperactivity, and interfering especially with academic, occupational, and social performance.

Attention Deficit Hyperactivity Disorder: Abbr. ADHD. Attention deficit disorder in which hyperactivity is present.

Autism: Autism is a complex developmental disability that typically appears during the first three years of life. The result of a neurological disorder that affects the functioning of the brain, autism impacts the normal development of the brain in the areas of social interaction and communication skills. Children and adults with autism typically have difficulties in verbal and non-verbal communication, social interactions, and leisure or play activities. Autism is one of five disorders coming under the umbrella of Pervasive Developmental Disorders (PDD), a category of neurological disorders characterized by ?severe and pervasive impairment in several areas of development. The five disorders under PDD are Autistic Disorder, Asperger?s Disorder, Childhood Disintegrative Disorder (CDD), Rett?s Disorder, and PDD-Not Otherwise Specified (PDD-NOS). Each of these disorders has specific diagnostic criteria as outlined by the American Psychiatric Association (APA) in its Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR).

Autism Spectrum Disorder (ASD): Autism is often referred to as a ?spectrum disorder,? meaning that the symptoms and characteristics of autism can present themselves in a variety of combinations, ranging from extremely mild to quite severe.

Behavior Disorder: A very general term used for any aberrant or maladaptive pattern of behavior that is sufficiently severe to warrant the attention of counselors or therapists. The term is preferred over any number of others previously used in this fashion, e.g., neurosis.

Cerebral Cortex: The outer portion of the brain where thought processes take place.

Childhood Disintegrative Disorder: Normal development for at least the first two years, significant loss of previously acquired skills.

Compulsive Behavior: Behaviors that are usually uncontrollable and often repetitive or obsessive.

Concordance: Agreement in types of data that occur in natural pairs?in autism a pair of identical twins is ?concordant? if BOTH are affected or unaffected. It is ?discordant? if one of them only is affected.

Cytomegalovirus Infection: a herpesvirus (genus Cytomegalovirus) that causes cellular enlargement and formation of eosinophilic inclusion bodies especially in the nucleus and acts as an opportunistic infectious agent in immunosuppressed conditions.

Developmental Disorders, Specific: A class of disorders that emerge during childhood characterized by disruption or delay in a specific area of perceptual or cognitive functioning that is independent of any other disorder.

Developmental Language Disorder: Developmental expressive language disorder is a disorder in which a child has lower-than-normal proficiency for his or her age in vocabulary, the production of complex sentences, and recall of words.

Disorder: An ailment that affects the function of mind or body.

Disease: Impairment of the normal state or functioning of the body as a whole or of any of its parts. One of the most common bases for classifying disease is according to cause. External factors that produce disease are infectious agents, including both microscopic organisms (bacteria, viruses, and protozoans) and macroscopic ones (fungi and various parasitic worms).

Dizygotic: Fraternal twins produced from two separate fertilized eggs. This is opposed to ?monozygotic? twins, which are twins produced from one fertilized egg in the mother.

Dopamine: A chemical transmitter in the brain similar to adrenaline. Dopamine affects brain processes that control movement, emotional response, and ability to experience pleasure and pain.

Double Blind: A type of study in which neither the subject taking the drug nor the investigator giving them the drug know whether it is the active, real drug or a placebo.

Echolalia: 1. Psychiatry: The immediate and involuntary repetition of words or phrases just spoken by others, often a symptom of autism or some types of schizophrenia. 2. An infant?s repetition of the sounds made by others, a normal occurrence in childhood development.

Epidemiologic, Epidemiology: The part of medical science that deals with the incidence, distribution, and control of disease in a population.

Etiology: The study of the causes or origins of a disease.

Event-Related Brain Wave Potentials, ERP: A method used to measure electrical response from portions of the brain during presentation of various stimuli such as a spoken word or a tone.

Executive Disorder: Deficits within (or lack of) the theory of mind module.

Face Fusiform Area: A region of the lateral part of the brain, the Fusiform Gyrus?, is active during the recognition of human faces in typically developing people.

Fenfluramine: These tablets work by decreasing the craving for food by altering neurochemical balances, and possibly by delaying passage of food along the gastrointestinal tract. It is suggested that it may reduce serotonin levels, since observations in children with autism show higher serotonin levels.

Fragile X Syndrome: A genetic disorder marked by a weak arm on the X chromosome. Affected males have large ears, large testicles, poor speech, and mental retardation; affected females are often subclinical. There is also a suspected link between fragile X syndrome and autism.

Functional MRI: A type of magnetic resonant imaging (MRI) scanning in which scientists can see what parts of the brain are active while a subject is performing a task, such as solving a math problem in the MRI scanner. Functional MRI (fMRI) can tell us which areas of the brain are active in some individuals with a disorder (e.g., those with autism) versus typically developing individuals.

Genetic Disorder: A pathological condition caused by an absent or defective gene or by a chromosomal aberration. Also called hereditary disorder, inherited disorder.

Gyrus: Measure of the brain?s electrical activity (potentials) in response to stimuli (events) in the environment. The most widely used stimuli are auditory or visual.

High-Functioning Autism: High-functioning autism is defined by children who are autistic by definition yet are able to communicate, do not have overly severe social impairments, and have only minor deficits in autism. Their IQ ratings are near normal, normal, or even high.

Heritable: Capable of being inherited or of passing on by inheritance from one individual to another.

Holistically: All together, as a unit; Concerned with wholes rather than analysis or separation into parts.

Idiosyncratic Language: (Idiosyncrasy n.) Attitude, behavior, or opinion peculiar to a person; anything highly individual or eccentric.

IQ: Intelligence quotient; the mental age divided by the chronological age and multiplied by 100.

Intraveneous infusion: A method for delivering a drug in solution by placing a catheter in a vein and ?infusing? or delivering the fluid with the active drug.

Language Disorder, Developmental: A general label used for a number of disorders evidenced by significant impairment in the development of language skills during childhood. The term is restricted to cases in which there is no known neurological or anatomical defect. Often the disorders are divided into the expressive types, in which vocal output is disordered but language comprehension is normal, and a mixed receptive-expressive type, in which both are impaired.

Learning Disorder: (Also referred to Learning Disability) Abbr. LD. Any of various cognitive, neurological, or psychological disorders that impede the ability to learn, especially one that interferes with the ability to learn mathematics or develop language skills.

Linear regression: A type of analysis of data?linear regression is used to make predictions about a single value. Simple linear regression involves discovering the equation for a line that most nearly fits the given data. That linear equation is then used to predict values for the data.

Melatonin: A naturally occurring hormone secreted by the pineal gland. In humans, it likely plays a role in establishing 24-hour (circadian) sleep rhythms.

Monozygotic twin: Identical twins produced from the same fertilized egg. This is opposed to dizygotic twins, which are twins produced from separate fertilized eggs in the mother.

MRI Scans: Magnetic Resonant Imaging?a type of imaging technique used to see internal structures of the body, especially soft tissues like the brain. An MRI image is superior to a normal X-ray image.

Multiplex Families: Those families in which there is more than one child with the disorder - i.e., autism.

Neuroleptics: Any of the powerful tranquilizers (as the phenothiazines) used especially to treat psychosis and believed to act by blocking dopamine nervous receptors -- called also antipsychotic.

Neurotransmitter: A chemical in the brain that transmits messages from one nerve cell to another.

Obsessive-Compulsive Disorder (OCD): A sub-class of anxiety disorders with two essential characteristics: recurrent and persistent thoughts, ideas and feelings; and repetitive, ritualized behaviors.

Oppositional Defiance Disorder (ODD): In children with Oppositional Defiant Disorder (ODD), there is an ongoing pattern of uncooperative, defiant, and hostile behavior toward authority figures that seriously interferes with the youngster?s day to day functioning.

Pancreas: An organ in the body that secretes chemicals (enzymes) helping digestion as well as insulin, which regulates blood sugar levels.

Partial Tetrasomy 15 Syndrome: Duke University researchers concluded that autistic children with a particular genetic profile may be a specific subtype that can be distinguished from other forms of autism. These children all have two copies of the same small region of chromosome 15, while people without autism only have one copy per chromosome.

Pediatrician: A doctor who specializes in treating children.

Peptides: Small proteins in the body.

Pervasive Developmental Disorders (PDD): Disorders characterized by severe and pervasive impairments in several areas of development such as social skills, communication skills, or stereotyped behaviors, interests, and activities. PDDs include several disorders including autism and Asperger disorder.

Pervasive Developmental Disorders-Not Otherwise Specified (PDD-NOS): This category of disorders is used in severe and pervasive impairment in social interactions, verbal/nonverbal skills, or certain behaviors and activities?but the criteria are not met for PDD. This may include ?atypical autism.?

Physiognomy: Specifically, the use of the face and facial expressions to judge mental abilities, character, emotional attitudes, etc.

Placebo: A ?dummy? medication (?sugar pill?) having no specific activity or action in the body. With a pill taken by mouth (orally), for example, the placebo is a pill identical in appearance to the pill with the active medicine. Subjects are given a placebo to test for the psychological aspects of giving the medicine?that is, some people complain of side effects (nausea, headache) and even improve with a placebo.

Prevalence: The percentage of a population that is affected with a specific disease at a given time.

Proband: The first member of a family to come to the notice of a researcher, and through whom investigation of a pedigree began. Normally the individual is selected because of the presence of a disorder whose inheritance is to be studied.

Prosody: Contrasting terms in prosody, orthography, and phonetics, used to discuss and mark the duration (or quantity) of speech sounds. In prosody, they refer to syllables and vowels; in orthography and related aspects of pronunciation, they focus principally on written vowels; in phonetics, they apply to spoken vowels and their written representations in IPA transcription.

Purine Disorders: A number of cases have been reported in medical literature in which classic autistic symptoms (a lack of social interaction and repetitive behaviors) are combined with an overproduction of purine compounds. This almost certainly represents some defect of purine metabolism, although no specific enzyme defect has been identified.

Putamen: A part of the brain, one of the three major areas that make up the basal ganglia, an area deep in the brain that organizes motor behavior.

Reactive Attachment Disorder: A disorder of childhood or infancy characterized by the failure of the child to develop normal social relatedness prior to the age of five. The disturbance is marked either by persistent failure of the child to initiate or respond appropriately to social interactions or (in older children) by indiscriminate sociability particularly with strangers and other socially inappropriate individuals.

Retrospective Study: A retrospective study is a study that looks backwards in time. When we study a disease that takes a long time to appear, we may need to use a retrospective study. A retrospective study may be one in which doctors examine the medical charts of patients that have a disease to find out if certain medications had any effect on them?they were treated in the past and therefore, the doctors are studying the patients retrospectively.

Rett?s Disorder: Progressive disorder which, to date, has occurred only in girls. Period of normal development and then loss of previously acquired skills, loss of purposeful use of the hands replaced with repetitive hand movements beginning at the age of 1-4 years.

Serotonin: A neurotransmitter in the brain involved in regulating mood and behaviors.

Serotonin re-uptake inhibitors (SSRI?s): A class of drugs that are used as anti-depressants. They increase the levels of serotonin (see above) in the body by inhibiting its re-uptake in the nerve cell.

Stimulants: An agent (as a drug) that produces a temporary increase of the functional activity or efficiency of an organism or any of its parts.

Tricyclic Antidepressants: Any of a group of antidepressant drugs (as imipramine, amitriptyline, desipramine, and nortriptyline) that potentiate the action of catecholamines and do not inhibit the action of monoamine oxidase.

Sources: Definitions acquired from various resources