Background: Symptoms of depression and anxiety are prevalent among Spanish university students. Minimally guided online interventions have shown promise in reducing symptomatology and preventing increased mental distress. There is a need to evaluate the effectiveness of guided preventive mental health interventions for depression and anxiety in university students.

Methods: two-arm multicenter randomized controlled trial (RCT), addressed to undergraduate students from 6 public universities with symptoms of depression and/or anxiety. Students will be evaluated through an online survey assessing mental health problems, use of mental health services, sociodemographic variables, self-perceived health, childhood and adolescent adversities, recent stressful events, social networks, personality and university experiences. A total of 600 students will be randomly assigned to: intervention group (guided E-health prevention intervention) or control group (treatment as usual with self-monitoring). The intervention, in app format, is based on principles of cognitive behavioral therapy, includes weekly feedback based on content and participation from a psychologist and self-monitoring. Assessments will take place post-intervention (up to 6 weeks), at 6 months and 12 months after randomization. The primary outcome will be the reduction of depressive or anxiety symptoms post-intervention, assessed with the Patient Health Questionnaire-9 (PHQ-9), the Generalized Anxiety Disorder-7 (GAD-7) and the Patient Health Questionnaire-Anxiety and Depression Scale (PHQ-ADS). Secondary outcomes of the RCT will be mental wellbeing, academic stress, comorbid symptoms, and adherence. Analyses will be conducted on an intention-to-treat and per protocol basis.

Discussion: The results of the PROMES-U RCT will provide valuable information on a guided preventive online intervention that could be delivered in the campus context. In addition, results will provide information on the positive impact of the intervention on other relevant factors involved in mental health among university students.

Inclusion Criteria:

• Eligible participants are all undergraduate students at the 6 participating universities and students followed in the PROMES-U observational study
• Having 18 years of age or more
• Having literacy in Spanish
• Having access to a smartphone (Android or Apple)
• With mild or moderate depression and/or anxiety symptoms screened (i.e., depression (5≤ (PHQ-9) ≤14); and/or anxiety (5≤ GAD-7 ≤14).

Exclusion Criteria:

• Moderately severe or severe depression and/or anxiety (i.e., PHQ-9≥15 and/or GAD-7≥15)
• High suicide risk
• A history of severe psychiatric disorder (e.g., bipolar, psychosis)
• Being on mental health treatment (i.e., medication, psychotherapy or other intervention)

Students with high suicide risk will receive a clinical alert recommending them to visit a specialist and a list of available mental health resources.