Genetic contributions to the development of ADHD subtypes from childhood to adolescence.
OBJECTIVE
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.


METHODS
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.
Larsson
Henrik
H
Drs. H. Larsson and Lichtenstein are with the Department of Medical Epidemiology and Biostatistics and Dr. J.-O. Larsson is with the Department of Women and Child Health, Child and Adolescent Psychiatric Unit, Karolinska Institutet, Stockholm.. Electronic address: Henrik.Larsson@meb.ki.se.
Lichtenstein
Paul
P
Drs. H. Larsson and Lichtenstein are with the Department of Medical Epidemiology and Biostatistics and Dr. J.-O. Larsson is with the Department of Women and Child Health, Child and Adolescent Psychiatric Unit, Karolinska Institutet, Stockholm.
Larsson
Jan-Olov
JO
Drs. H. Larsson and Lichtenstein are with the Department of Medical Epidemiology and Biostatistics and Dr. J.-O. Larsson is with the Department of Women and Child Health, Child and Adolescent Psychiatric Unit, Karolinska Institutet, Stockholm.
D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000175:diagnosis* / Q000235:genetics* / Q000523:psychology; D002648:Child; D039721:Diagnostic and Statistical Manual of Mental Disorders; D018450:Disease Progression; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D011795:Surveys and Questionnaires