The Serotonin Transporter in Attention Deficit Hyperactivity Disorder

The Serotonin Transporter in Attention Deficit Hyperactivity Disorder Investigated With Positron Emission Tomography

The aim of the present proposal is to prove that adult attention deficit hyperactivity disorder (ADHD) patients show lower serotonin transporter (5-HTT) binding using positron emission tomography (PET) and the selective radioligand [11C]DASB. Specifically, the 5-HTT binding will be quantified in 20 adult medication-free ADHD patients (50% females) and in 20 age- and sexmatched healthy controls. Investigating untreated adult ADHD patients without any psychiatric comorbidities will provide the opportunity to estimate the change of serotonin transporter binding in adult ADHD patients compared to a group of healthy controls. Several lines of evidence support the hypothesis that serotonergic neurotransmission may, in addition to dopamine, play an important role in the aetiology of ADHD. So far, no PET study investigating serotonergic neurotransmission in adult ADHD patients has been conducted, although alterations in the serotonin system may be substantially involved in the susceptibility and subtype characterization of ADHD.

Inclusion Criteria:

• Patients must be male or female outpatients who are at least 18 years of age and no more than 65 years of age when informed consent is obtained.
• Patients must meet DSM-IV-TR criteria for current ADHD as well as for historical diagnosis of ADHD during childhood as assessed by the Conner´s Adult ADHD Diagnostic Interview for DSM-IV (CAADID, Conners 1999).
• Patients must have a score of >2 on at least 6 items of either the inattentive or hyperactive score subscales at screening on the rated CAARS-Inv:SV (Conners 1999). In addition, their CAARS-Inv:SV 18-item total ADHD symptom score (the sum of the inattention and hyperactivity/impulsivity subscales) must be >20.
• Patients must have a CGI-ADHD-S score of >4 (moderate symptoms) at screening.
• Patients must be physically healthy.
• Patients must be able to understand and willing to sign the written informed consent document.

Exclusion Criteria:

• Patients suffering from severe somatic diseases will be excluded from the study.
• Any treatment with stimulants, selective norepinephrine reuptake inhibitors or any other psychotropic treatments, such as SSRIs, etc. within six months prior to screening.
• Patients suffering from any current comorbid psychiatric disorder (Axis I or Axis II diagnosis according to DSM-IV-TR) will be excluded.
• Patients who are currently using alcohol, drugs of abuse, or any medication in a manner which is indicative of chronic abuse or who meet DSM-IV-TR criteria for alcohol or other substance dependence.
• Any implant or stainless steel graft.
• Positive urine pregnancy test.
• Participation in studies with PET or SPECT within the last 10 years.