This is a parallel arm randomized (1:1) controlled trial. Adolescents aged 12-17 years (n=228) who are starting or changing a selective serotonin reuptake inhibitor (SSRI) for depression and/or anxiety will be randomly allocated to receive 12-weeks of pharmacogenetic-guided antidepressant therapy (experimental intervention) or current prescribing guidelines/recommendations guided therapy (control intervention).

Goal: To test the efficacy of pharmacogenetic-guided antidepressant prescribing for adolescents with depression.

Background: For an adolescent with depression and anxiety, antidepressant medication is prescribed, often in combination with psychotherapy. The class of antidepressants recommended for use is selective serotonin reuptake inhibitors (SSRIs) with fluoxetine recommended as the first-line medication, and four other SSRIs recommended for consideration (sertraline, citalopram, escitalopram, fluvoxamine) if the adolescent does not respond or tolerate fluoxetine. For most adolescents, medication prescribing, and monitoring will be managed by a primary care physician or community pediatrician rather than by a mental health care provider, and guidelines exist to support this management. However, current prescribing guidelines/recommendations do not account for SSRI metabolism phenotypes that could change whether the SSRI selected is efficacious or tolerated. Our team of researchers, clinician scientists, patient partners, and primary care providers has designed a trial to test the impact of accounting for metabolism phenotypes, through pharmacogenetic-guided antidepressant prescribing, on adolescent outcomes, experiences, and health care utilization.

Principal Question: Compared to current prescribing guideline/recommendation informed prescribing, does pharmacogenetic-guided prescribing for adolescents with depression and/or anxiety have superior efficacy following 12-weeks of therapy with a SSRI?

The Trial: This is a parallel arm randomized controlled trial. Adolescents aged 12-17 years (n=228) who are starting or changing a SSRI for depression and/or anxiety will be randomly allocated to receive pharmacogenetic-guided antidepressant therapy (experimental intervention) or current prescribing guideline/recommendation guided prescribing (control intervention). Participants and prescribing physicians will be blinded to which intervention was received. The primary outcome is depressive symptom remission at 12 weeks measured using the Quick Inventory of Depressive Symptomatology - Adolescent (17-item) (QIDS-A17) and anxiety symptom remission at 12 weeks measures using the Screen for Child Anxiety Related Disorders (SCARED). Secondary outcomes include side effects, role functioning, medication adherence, and health-related quality of life measured 4-, 8-, and 12-weeks after intervention initiation as well as cost-effectiveness.

Inclusion Criteria:

• Age 12-17
• Depression and/or anxiety as the primary concern, confirmed by the treating physician
• Intention to start a new SSRI
• English fluency

Exclusion Criteria:

• Co-occurring obsessive compulsive disorder, psychosis, bipolar disorder, eating disorder, autism spectrum disorder, fetal alcohol spectrum disorder, or intellectual disability
• History of non-response to 3 or more SSRI medications as confirmed by the treating physician
• Brain stimulation-based therapy initiated within 8 weeks of referral, or plans to initiate/change brain stimulation during study participation
• History of liver or hematopoietic cell transplant
• History of CYP2B6, CYP2C19, or CYP2D6 testing

Anonymized, individual participant PGx-GAP data will be shared using a controlled-access model. Under this model, the data will be released to a researcher if access criteria are met.

All requests for data sharing should be made to the Co-Principal Investigators who will be responsible for reviewing and granting requests. Requestors should provide a research proposal for review. In the event that a data sharing request is declined, reasons will be provided to the requestor. If the data sharing request is granted, a data-sharing agreement will be initiated by the Co-Principal Investigators alongside the University of Calgary (lead institution). This agreement will include information on the individual data to be shared; if other documents will be available (e.g., statistical codes, data dictionary), when the data will be available and for how long, and how data access will be provided (e.g., file transfer).

1. The requestor is affiliated with an academic institution as an independent investigator or trainee of an independent investigator;
2. The proposed research question(s) and hypothesis(es) are specific, measurable, and achievable;
3. The proposed research project will be governed/overseen by a local legal/regulatory body;
4. The proposed research project poses no risk of invasion of privacy or breaches of confidentiality for trial participants;
5. A member of the proposed research team has sufficient statistical skills to carry out the proposed analytic plan;
6. The requestor has sufficient financial and/or human resources to see the proposed research project to completion;
7. The proposed research question(s) and hypothesis(es) do not conflict with active or planned studies of the Co-Principal Investigators.

Participants, their prescribing physician, and the investigator will all be blinded to study arm. The study coordinator will be the only one unblinded to study arm allocation.