Major Depression (MD) is highly prevalent and has associated a high burden and economic costs. Mild levels of MD could be treated without antidepressants at Primary Care (PC).

Main objectives: 1) To calculate the cost-effectiveness of active monitoring (recommended by NICE) vs pharmacological antidepressant treatment to treat mild MD at PC level.

Methods: 300 patients (≥18 years) with MD (diagnosed by the GP) will be recruited at the PC center. Depending on the level of symptoms, the GP will choose between: A) Active Monitoring (n=150) and B) pharmacological treatment (n=150).

Patients will be followed-up for one year and data will be collected at baseline, 6 and 12 months. Severity will be assessed by Patient Health Questionnaire (PHQ-9), quality of life with the EuroQoL-5D (5 health dimensions), and the use of services with an adapted version of the Client Service Receipt Inventory (including lost productivity).

Cost-effectiveness and cost-utility analysis will be calculated and 5000 bootstrapping replications will be conducted to asses uncertainty. Cost-acceptability curves will be done using two perspectives: the National Health Service perspective and the Societal perspective.

The Propensity Score technique will minimize the absence of randomization, matching cases from both treatment options.

Inclusion Criteria:

1. Patients whose GP considers to have major depression. The indication of pharmacological or non-pharmacological treatment will be based strictly on the clinical judgment of the physician.
2. Adults (≥18 years)
3. Informed consent signed by the physician and the patient to participate in the study.

Exclusion Criteria:

1. Use of antidepressant drugs during the previous 60 days to inclusion date.
2. Alcohol or other toxic abuse.
3. Psychosis or bipolar disorder identified in the psychiatric interview
4. Use in the last 6 months of antipsychotic drugs, lithium or antiepileptic
5. Health status (pregnancy) and / or disease and / or treatments that contraindicate the use of antidepressant drugs.
6. Terminal illness.

Primary care patients who suffer from major depression.