ADHD Research Today is a free monthly online journal that collates and summarizes the latest research about ADHD, including details on attention-deficit hyperactivity disorder, drugs, treatment, symptoms. | ||||||||
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Genetic contributions to the development of ADHD subtypes from childhood to adolescence.Larsson H, Lichtenstein P, Larsson JO Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm. Henrik.Larsson@meb.ki.se OBJECTIVES: Little is known about how genes influence the development of symptoms included in the DSM-IV subtypes of attention-deficit/hyperactivity disorder (ADHD) from childhood to adolescence. The aim of this study was to examine genetic influences contributing to the development of hyperactive-impulsive symptoms and inattentive symptoms of ADHD from childhood to adolescence. METHOD: The sample included all 1,480 twin pairs born in Sweden between May 1985 and December 1986. Parents responded to mailed questionnaires on three occasions, when the twins were 8 to 9, 13 to 14, and 16 to 17 years old. The authors used dimensional scales of hyperactivity-impulsivity and inattention derived from a checklist of items based on the DSM symptoms of ADHD. RESULTS: Symptoms of hyperactivity-impulsivity declined with increasing age, whereas there was no decline in symptoms of inattention. Persistent genetic influences explain between 45% and 90% of the total genetic variance in hyperactivity-impulsivity and inattention across age. Persistent genetic variance was primarily operating across subtypes, even though persistent subtype-specific influences were also significant. CONCLUSIONS: The finding of persistent cross-subtype (i.e., combined) and persistent subtype-specific genetic influences (i.e., primarily hyperactive-impulsive and primarily inattentive) are in line with a genetic basis for the DSM-IV classification of ADHD subtypes. Published 25 July 2006 in J Am Acad Child Adolesc Psychiatry, 45(8): 973-81.
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