Pharmacogenomics of Selective Serotonin Reuptake Inhibitor (SSRI)-Induced Behavioural Activation

Inclusion criteria: Participants will be eligible for participation if all of the following are true. * Resident of Manitoba * Age, 6 - 24 years * Diagnosis of major depressive disorder (MDD), anxiety disorder, or obsessive-compulsive disorder (OCD) * Current or past history of selective serotonin reuptake inhibitor (SSRI), e.g., Citalopram \[Celexa\], Escitalopram \[Cipralex\], Fluoxetine \[Prozac\], Fluvoxamine \[Luvox\], Sertraline \[Zoloft\], Paroxetine \[Paxil/Plaxil CR\]) therapy * \[Cases Only\] Have experienced behavioural side effects after taking an SSRI that resolved after reducing the dose or discontinuation of the drug * \[Controls Only\] Did not experience any side effects after taking an SSRI for eight (8) continuous weeks Exclusion criteria: Participants will be excluded from participation if any of the following are true. * Inability of parent/legal guardian/mature minors to give informed consent * Inability of the child (6 - 13 years) to give informed assent * Unwillingness of the child to provide a saliva sample for genetic analysis * Current, past, or suspected diagnosis of attention deficit hyperactivity disorder (combined or hyperactive type), oppositional defiant disorder, conduct disorder, bipolar disorder, psychotic disorder, pervasive developmental disorder * History of liver or bone marrow (hematopoietic cell) transplant.