The main goal of the study is to test the efficacy of tDCS in combination with the Unified Protocol for transdiagnostic treatment of emotional disorders, to reduce anxiety symptoms in a mixed anxiety disorders sample, as assessed by the Hamilton Anxiety Rating Scale (HARS; Hamilton, 1959).

Participants will be randomly allocated to one of four parallel experimental arms, within a 2X2 factorial design in which two interventions (tDCS and CBT-UP) will be delivered, and assessed according to two levels (e.g., intervention vs. no intervention).

Each study participant will assigned to one factor level. Four intervention groups are defined

1. active tDCS + CBT-UP
2. sham tDCS + CBT-UP
3. active tDCS + Psychoeducation
4. sham tDCS + Psychoeducation

The four arms allow to experimentally control the two active therapeutic interventions: active tDCS and CBT-UP. Sham tDCS is the control for active tDCS and psychoeducation is the control condition for CBT-UP.

The intervention will last for 15 weeks, and all groups will comply with the same intervention structure according to the examination plan established in the protocol:

• week 1-2: 1 CBT-UP session/week
• week 3-4: 5 tDCS sessions and 1 CBT-UP session/week
• week 5-8: 2 tDCS sessions and 1 CBT-UP session/week
• week 9-14: 1 tDCS session and 1 CBT-UP session/week
• week 15: 1 CBT-UP session

The treatment will consist of 26 transcranial direct current stimulation sessions, each lasting 20 minutes, with a current intensity of 2 mA, the cathode placed over the right dorsolateral prefrontal cortex and the anode placed over the left deltoid muscle. tDCS will be combined with cognitive-behavioral therapy, in particular following the unified protocol for transdiagnostic treatment of emotional disorders (Barlow et al. 2018).

Safety:

No serious adverse effects are expected with conventional tDCS protocols in humans (≤40 min, ≤4 mA; conclusions from a meta-analysis observing >33200 sessions, >1000 subjects with repeated sessions; Bikson et al., 2016).

Plans for treatment or care after the subject has ended his/her participation in the trial:

Patients will be recommended and offered the best treatment as evidenced by the trial results. For patients that already completed that intervention further standard psychological/psychiatric treatment will be recommended according to patients' status.

Inclusion Criteria:

• Diagnosis of generalized anxiety disorder, specific phobia, panic disorder, agoraphobia, or social anxiety disorder.
• Willing to participate and to give written informed consent

Exclusion Criteria:

1. Contra-indications to tDCS use:

   • Presence of a cardiac or neurological condition
   • Metallic implants
   • If contact with scalp is not possible
   • Have had a head injury resulting in a loss of consciousness that has required further investigation
   • History of seizures
   • Epilepsy or a history of epilepsy
   • Past adverse effects with non-invasive stimulation treatments

2. Current diagnosis of another psychiatric disorder (except for depression, as long as secondary diagnosis), psychoactive medication or psychological treatment

3. Left-handedness

4. Pregnancy

5. Skin condition on the stimulation target area

6. Recreational drug use