[Biochemical bases and research in attention-deficit hyperactivity disorder].
BACKGROUND
Attention deficit hyperactivity disorder (ADHD) is a complex neurodevelopmental disorder, which is very common among the school aged population. Its core symptoms are inattention, hyperactivity, and impulsivity. Currently, three principal subtypes of ADHD are recognized: ADHD predominantly inattentive type, ADHD predominantly hyperactive/impulsive type or ADHD combined type. Affected individuals have increased comorbidity risks, often followed by cognitive, emotional and/or social impairments as adults. Stimulants drugs such methylphenidate (Ritalin) or D amphetamine (Dexedrine) represent the first line drugs for the treatment of ADHD.


METHODS
The clinical features of ADHD were first described by Dr. George Frederick Still for Lancet in 1902, and in spite of the investigations carried out since then, the precise cause is still not clear. The purpose of this review is to describe recent advances of the neurobiological basis of ADHD.


CONCLUSIONS
Recent neuroimaging studies in humans indicate a dysfunctions of the frontal striatal circuits in patients with ADHD, which can be improved by pharmacological treatment. Both pre and clinical studies implicate a dysregulation of the dopaminergic and noradrenergic systems, which are known to regulate the functions of these circuits. More recent evidence indicate that some features of ADHD could be linked to alterations in the posterior inferior vermis. These studies also stress the importance of taking into consideration factors such as age, gender and duration of pharmacological treatment when interpreting the results.
Díaz-Heijtz
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Neuropediatric Unit, Department of Womand and Child Health, Astrid Lindgren Children Hospital, Karolinska Institutet, Stockholm, Sweden. Rochellys.Heijtz@home.se
D000328:Adult; D001289:Attention Deficit Disorder with Hyperactivity / Q000145:classification / Q000188:drug therapy / Q000503:physiopathology*; D000697:Central Nervous System Stimulants / Q000627:therapeutic use; D002648:Child; D006801:Humans
D000697:Central Nervous System Stimulants