The purpose of this research is to learn more about how children with mental health problems, including bipolar disorder (BD), attention deficit hyperactivity disorder (ADHD), and generalized anxiety disorder (GAD), differ from children without these problems. The investigators want to understand how these 4 groups of children differ in brain activity, function, and structure.

This study has 2 visits (total time ~6 hours):

Visit #1 (2-3 hours), includes: (a) detailed description of study and study consent, (b) interviews about the child's mental health, mood, and behavior, and (c) a screening IQ test (word games, playing with blocks).

If a child fits our study criteria, they will play some special computer games, provide a spit sample for DNA, and parents/children will complete questionnaires.

All children fitting our study criteria, will also be invited to complete visit #2 (2 hours) consisting of a special MRI brain scan at Brown University (Providence, RI). To make sure all children feel comfortable in the MRI, they will spend time in our practice MRI (i.e., "MRI simulator") that looks and sounds just like the real MRI. During the actual MRI, children will play a computerized game in which they can win and lose points. The MRI lasts one and a half hours (at most).

Participants are compensated for their time.

General Inclusion Criteria:

• English- speaking,children & adolescents between the ages of 7- 17
• consenting parent/guardian

General Exclusion Criteria:

• estimated IQ less than 70
• substance/alcohol use or dependence within the last 2 months
• Autism Spectrum Disorders or primary psychosis
• medical/neurological conditions that mimic the psychiatric disorders of interest
• implanted metal (NO BRACES or COCHLEAR IMPLANT)

For inclusion in the Bipolar group, participants:

• have to meet Diagnostic and Statistical Manual, 4th Edition Text Revision (DSM-IV-TR) criteria for BD Type I, including at least one lifetime episode of mania

For inclusion in the ADHD/ADD group, participants:

• meet DSM-IV-TR criteria for any subtype of ADHD or ADD
• can not currently meet diagnostic criteria for bipolar, depressive or anxiety disorders

For inclusion in the Generalized Anxiety Group (GAD), participants:

• have to meet DSM-IV-TR criteria for GAD
• can not currently meet diagnostic criteria for Obsessive Compulsive Disorder (OCD) or Post-Traumatic Stress Disorder (PTSD)

For inclusion in the Healthy Control group, participants:

• can not have a past/current history of psychiatric or substance use disorders
• can not have a first-degree relative (parents, brothers/sisters) with a history of psychiatric illness

Participants will be recruited from in and around the Providence. Rhode Island area