• INCLUSION CRITERIA:
• Adults with a history of PD who have eligible children (see exclusionary criteria for offspring below) between the ages of 9 and 20 years.

EXCLUSION CRITERIA:

• Serious, unstable illnesses including hepatic, renal, gastroenterologic, respiratory, cardiovascular, endocrinologic, neurologic, immunologic, or hematologic disease; one or more past seizures without a clear and resolved etiology; subjects who are currently at high risk for homicide or suicide; subjects with psychotic features, and subjects with current DSM-IV substance abuse or dependence within the past year.
• The individual conducting the telephone screen also will ask the parent questions about their child(ren). Exclusionary criteria for children include: psychosis, mania, pervasive developmental disorder, use of psychotropic medication, an IQ less than 70, and acute medical conditions (e.g., asthma).
• Child participants must be psychotropic free for at least 14 days prior to the CO2 challenge session.
• For children taking fluoxetine, they must be free of this medication for at least 4 weeks.
• We will not take any child participant off their medication to participate in this study.
• The proband parent must be a legal guardian of the child to qualify for the study.
• Families passing screening criteria will be scheduled for an intake to complete a clinical interview, questionnaires, and CO2 challenge task with assessment of respiratory physiology.