tDCS for Social Media Addiction

The goal of this clinical trial is to learn whether transcranial direct current stimulation (tDCS), a non-invasive brain stimulation, can reduce "craving" and problematic levels of social media/internet use in university students.

The main questions it aims to answer are:

* Does active tDCS reduce craving to use social media during the intervention period compared with sham stimulation and no stimulation? * Does active tDCS reduce internet/social media addiction severity (measured with the Internet Addiction Test, IAT) compared with sham stimulation and no stimulation, and are any effects still present at follow-up? Researchers will compare three groups-active tDCS, sham tDCS (a simulation where stimulation is stopped after the first seconds), and a control group (no stimulation)-to see whether changes are due to tDCS rather than placebo effects or time.

Participants will:

* Complete an initial screening and baseline questionnaires (a sociodemographic questionnaire and the IAT). * Be randomly assigned to one of three groups: active tDCS, sham tDCS, or control (no stimulation). * Complete the IAT again after the intervention and again about 5 weeks later (follow-up), along with questions about social media use habits.

During intervention, participants in active tDCS and sham tDCS will:

* Attend 10 sessions over 2 consecutive weeks (Monday-Friday), with each session lasting about 30 minutes; mobile phone use is not allowed during sessions. * Rate craving on a Visual Analogue Scale (VAS) at the start and end of each session.

This study will be conducted with university students in the Greater Lisbon area and will follow double-blind procedures for the active vs sham conditions (participants and researchers will not know the assigned condition until the end of the study).