This is an 8-week open-label study aimed at assessing the effectiveness and tolerability of Quetiapine, in the treatment of preschool children aged 4 to 6 years with bipolar and bipolar spectrum disorder. This is an exploratory, pilot study, seeking to determine whether Quetiapine is efficacious and well tolerated in the treatment of preschoolers with pediatric bipolar and bipolar spectrum disorder in this age group. The study results will be used to generate hypotheses for a larger randomized controlled clinical trial with explicit hypotheses and sufficient statistical power.

Seroquel is a psychotropic agent that affects multiple neurotransmitter receptors in the brain: serotonin 5HT1A and 5HT2, dopamine D1 and D2, histamine H1 (IC50=30nM), and adrenergic receptors.

This is an 8-week open-label study aimed at assessing the effectiveness and tolerability of Quetiapine, in the treatment of preschool children aged 4 to 6 years with bipolar and bipolar spectrum disorder. This is an exploratory, pilot study, seeking to determine whether Quetiapine is efficacious and well tolerated in the treatment of preschoolers with pediatric bipolar and bipolar spectrum disorder in this age group. The study results will be used to generate hypotheses for a larger randomized controlled clinical trial with explicit hypotheses and sufficient statistical power.

Inclusion Criteria:

• Male or female subjects, 4-6 years of age.
• Subjects must have a DSM-IV diagnosis of bipolar I, bipolar II disorder or bipolar spectrum disorder and currently displaying manic, hypomanic, or mixed symptoms (with or without psychotic features) according to the DSM-IV based on clinical assessment and confirmed by structured diagnostic interview (Kidd Schedule of Affective Disorders and Schizophrenia Epidemiological Version). Bipolar spectrum disorder (or sub-threshold bipolar disorder) is operationalized as having severe mood disturbance, which meets DSM-IV Criteria A for bipolar disorder but meet fewer elements in criteria B (only require 2 items for elation category and 3 for irritability).
• Subjects and their legal representative must have a level of understanding sufficient to communicate intelligently with the investigator and study coordinator, and to cooperate with all tests and examinations required by the protocol.
• Subjects and their legal representative must be considered reliable.
• Each subject and his/her authorized legal representative must understand the nature of the study. The subject's authorized legal representative must sign an informed consent document.
• Subjects must have an initial score on the Young Mania Rating Scale (Y-MRS) total score of at least 20.
• Subject must be able to participate in mandatory blood draws.
• Subjects with comorbid Attention Deficit Hyperactivity Disorder (ADHD), Oppositional Defiant Disorder (ODD), Conduct Disorder (CD), anxiety and depressive disorders will be allowed to participate in the study provided they do not meet for any of the exclusionary criteria.
• For concomitant stimulant therapy used to treat ADHD, subjects must have been on a stable dose of the medication for 1 month prior to study enrollment. The dose of the stimulant therapy will not change throughout the duration of the study.

Exclusion Criteria:

• Investigator and his/her immediate family; defined as the investigator's spouse, parent, child, grandparent, or grandchild.
• Serious, unstable illness including hepatic, renal, gastroenterological, respiratory, cardiovascular (including ischemic heart disease), endocrinologic, neurologic, immunologic, or hematologic disease.
• Uncorrected hypothyroidism or hyperthyroidism.
• History of severe allergies or multiple adverse drug reactions.
• Non-febrile seizures without a clear and resolved etiology.
• Leukopenia or history of leukopenia without a clear and resolved etiology.
• Judged clinically to be at serious suicidal risk.
• Any other concomitant medication with primarily central nervous system activity other than specified in Concomitant Medication portion of the protocol.
• A non-responder or a history of intolerance to an adequate trial of Quetiapine(2 months or more at an adequate dose) as determined by the clinician.
• Current diagnosis of schizophrenia.
• Non English speaking subjects will not be allowed into the study for the following reasons: a) the assessment instruments are not available and have not been adequately standardized in other languages; b) our clinical trials facility is located in Cambridge and not in the MGH main campus without the availability of translators; c) psychiatric questionnaires and evaluations are taxing and adding the complexity of a translator has the potential to make the patient experience even more exhausting.