The aim of the present study is to investigate the effect of prefrontal transcranial Direct Current Stimulation (tDCS) on clinical severity, attentional bias and interoceptive accuracy in panic disorder (PD).

The participants will be assigned to active and sham groups (1:1) and will receive 10 sessions of tDCS. The study will also examine if the effects may last for a month.

Panic Disorder (PD) is one of the most common anxiety disorders. In spite of several available medications, there are unsatisfactory outcomes in a considerable proportion of PD patients and novel treatment approaches are lacking. Given that response to pharmacotherapeutical and psychological treatments occur after long intervals and medications may cause substantial adverse effects which may affect treatment compliance, fast acting and well-tolerated treatments such as non-invasive brain stimulation are considered to be useful as primary treatment approach or as an add-on treatment in PD. Repetitive Transcranial Magnetic Stimulation (rTMS) trials targeting prefrontal cortex mostly reported favorable outcomes in PD.

Transcranial Direct Current Stimulation (tDCS) is another promising non-invasive brain stimulation method with numerous distinctive aspects including its low-cost, robust safety and tolerability, low dropout rates, easy application, reliable blinding procedures and the opportunity to use concomitantly with other treatments. Left anodal/right anodal tDCS over the dorsolateral prefrontal cortex has been demonstrated to decrease attentional bias and amygdala reactivity to threat in individuals with high trait anxiety. Moreover, a treatment-resistant case of PD was reported to have significant amelioration of symptoms up to one month after 10 sessions of tDCS.

The study is a triple-blind randomized controlled trial. The sample will be consisted of thirty participants diagnosed as having PD due to Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria. The participants will be assigned to active or sham groups equally. Clinical severity will be assessed with adequate scales. Emotion recognition, attentional bias to threat and interoceptive accuracy will also be measured. Then, participants will be applied ten active or sham sessions of left anodal/right cathodal tDCS over the dorsolateral prefrontal cortex (DLPFC). All measurements will be repeated after the applications. Succinctly, the aim of this study is to assess the effect of ten sessions left anodal/right cathodal tDCS over the DLPFC on clinical severity, attentional bias and interoceptive accuracy in PD.

Inclusion Criteria:

• Patients with a primary diagnosis of Panic Disorder, as confirmed by the Structured Clinical Interview for the DSM-5 (SCID-5);
• Patients currently on medication must be at the same stable dose(s) for one month prior to enrollment and be willing to continue at the same dose(s) through the duration of the study;
• Right-hand dominancy assessed by Edinburgh Handedness Inventory;
• Willingness and ability to comply with the requirements of the study protocol;
• Naïve to tDCS.
• 5 or more years of education

Exclusion Criteria:

• Illiteracy, deficient language or refusal to participate or being not able to follow instructions or complete study tasks;
• Less than 5 years of education
• Individuals with any current or lifetime diagnosis of other Axis I disorders, as confirmed by the Structured Clinical Interview for the DSM-5 (SCID-5);
• History of substance or psychoactive compound use,with the exception of nicotine consumption;
• The presence of mental retardation diagnosis (previously identified)
• Individuals with a clinically defined neurological disorder, with an increased risk of seizure for any reason, with a history of treatment with rTMS, deep brain stimulation for any disorder will be excluded;
• Any personal or family history (1st degree relatives) of seizures other than febrile childhood seizures
• Personal history of head trauma that resulted in loss of consciousness for > 5 minutes and retrograde amnesia for > 30 minutes;
• Significant hearing loss or visual impairment;
• Diagnosis of any serious or uncontrolled medical condition such as chronic obstructive pulmonary disease, congestive heart failure or renal failure;
• Skin diseases that could potentially cause irritations under electrodes;
• Patients missing two consecutive protocol sessions;
• Patients with cardiac pacemakers, implanted medication pumps, intracardiac lines, or acute, unstable cardiac disease, with intracranial implants (e.g. aneurysm clips, shunts, stimulators, cochlear implants, or electrodes) or any other metal object within or near the head, excluding the mouth, that cannot be safely removed will be excluded.