• INCLUSION CRITERIA:

For both the U.S. and the Columbian Studies, we plan to obtain blood samples from subjects meeting the following criteria:

Children , ages 7-17, affected with ADHD with siblings who are either affected or unaffected, and their parents. (in the Columbian Study, we will also gather information and blood samples from extended families).

Adult participants 18 years or older selected for MRS from the Paisa population will be included if they:

1. share the haplotype that is in linkage disequilibrium at chormosome 11 p
2. do not have devices such as pace makers, cochlear implants, metal clips in the brain, etc that would preclude them from undergoing magnetic resonance technology
3. are not pregnant (pregnancy test will be administered) or breastfeeding

4. do not have a mental condition such as claustrophobia which would make magnetic resonance tehcnology unacceptable to them.

   EXCLUSION CRITERIA:

   Exclude the following (if the condition could cause false positive ADHD):

   • Prematurity
   • Neurological conditions
   • Cardiac surgery
   • Prenatal drug exposure
   • Hydrocephaly
   • Mental Retardation (IQ of less than 80)
   • Known genetic syndromes
   • Known CNS disorders
   • Known lead toxicity
   • Tourette Disorder
   • Obsessive-Compulsive Disorder
   • Major Depression on both proband and affected sibling
   • Pervasive Developmental Disorder
   • Age under 7 years old
   • Autism
   • Other Psychoses
   • Post Traumatic Stress Disorder
   • Language Disorder (if known)
   • Severe Sensory Impairment (visual and hearing).

   No bilineal families for statistical reasons are to be included, i.e. families in which both father and mother are known to be affected with ADHD. In order to involve either parent, there must be affected siblings.

   Include, but note:

   • Oppositional Defiant Disorder
   • Conduct Disorder
   • Tic Disorder
   • Obsessive/Compulsive Symptoms
   • Anxiety/Phobias
   • Learning Disabilities.