This study will focus on a population of antipsychotic (AP) naïve adolescents and young adults and will measure fat accumulation in relation to exposure to atypical antipsychotic medications.

Atypical Antipsychotics (AAPs) are known to cause metabolic dysfunction, and adolescents are especially vulnerable to this effect. The anthropometric measures routinely used to monitor these metabolic side effects may, in fact, underestimate risk in the pediatric population as they are not a good index of hepatic and visceral adipose tissue.

This study will measure fat accumulation over a 12 week period in adolescents and young adults taking an AAP for the first time. MRI imaging will measure hepatic, and visceral adipose tissue at baseline and study end. An Oral Glucose Tolerance Test will measure glucose resistance and insulin sensitivity. In an exploratory fashion, investigators will also image the brain to assess for volumetric changes which may occur in association with AAP treatment and changes in metabolic indices.

Inclusion Criteria:

• AP naïve or AP-free for 3 months or greater
• prescribed an AP for treatment
• age 12-35
• using contraceptive (females of child bearing age)

Exclusion Criteria:

• currently taking AP or been taking AP for greater than 1 week within the past 3 months
• pregnant or planning to become pregnant
• eating disorder (active or previous)
• clinical or laboratory evidence of uncompensated cardiovascular, endocrine, haematological, or pulmonary disease
• major medical or surgical event in the preceding 3 months
• acute suicidal risk

Participants recruited will be selected from clinical settings. Participants will be flagged by their care provider and offered the opportunity to participate should they meet criteria. As well, participants who are interested in the study and may meet criteria can refer themselves to the study.