This is an open-label pilot clinical trial to evaluate the effects of transcranial alternating current stimulation (tACS) in adults diagnosed with generalized anxiety disorder (GAD) and chronic primary insomnia. The study will involve 30 participants who will receive 20 sessions of tACS over four weeks. The stimulation will be delivered at 15 mA and 77.5 Hz using the Nexalin device. The main goal is to assess improvements in anxiety and sleep quality. Results from this study will provide preliminary evidence for future randomized controlled trials.

Generalized Anxiety Disorder (GAD) and chronic primary insomnia are highly prevalent and frequently co-occurring psychiatric conditions associated with significant functional impairment and reduced quality of life. Both disorders are characterized by dysregulation of cortical and subcortical neural circuits involved in emotional regulation and sleep-wake control, including abnormal oscillatory activity in fronto-limbic networks. Although pharmacological and psychotherapeutic interventions are considered first-line treatments, a substantial proportion of patients remain symptomatic or experience adverse effects, highlighting the need for novel neuromodulatory strategies.

Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that delivers low-intensity sinusoidal electrical currents at specific frequencies to entrain endogenous neural oscillations. By modulating frequency-specific cortical rhythms, tACS may influence neural synchrony and connectivity patterns implicated in anxiety and sleep disturbances.

The present study is an open-label, single-arm pilot clinical trial designed to investigate the feasibility, safety, tolerability, and preliminary clinical effects of tACS in adults with GAD and chronic insomnia. Participants will undergo 20 stimulation sessions administered over four consecutive weeks (five sessions per week). Stimulation will be delivered using the Nexalin device at a frequency of 77.5 Hz and an intensity of 15 mA. Electrodes will be positioned over the frontal pole (Fpz) and bilateral mastoid regions according to the international 10-20 EEG system.

Clinical assessments will be conducted at baseline, at the end of the 4-week treatment phase, and at a 4-week post-treatment follow-up visit. The study will examine changes in anxiety severity, sleep quality, mood symptoms, global clinical status, and cognitive/functional performance to characterize the potential therapeutic effects of this intervention.

The trial will be conducted at the Interdisciplinary Neuromodulation Service of the Institute of Psychiatry, Hospital das Clínicas, University of São Paulo Medical School (IPq-HCFMUSP). Findings from this pilot study are intended to inform the design of future randomized, sham-controlled clinical trials and contribute to the expanding investigation of transcranial alternating current stimulation as a potential treatment modality in anxiety and sleep disorders.

Inclusion Criteria:

Age between 18 and 65 years; Diagnosis of Generalized Anxiety Disorder (GAD) based on Diagnostic and Statistical Manual of Mental Disorders (DSM) criteria; Diagnosis of chronic primary insomnia; Hamilton Anxiety Rating Scale (HAM-A) score ≥15 at screening, indicating at least moderate anxiety severity; Score >5 on the Pittsburgh Sleep Quality Index (PSQI); Stable use of antidepressants (SSRI or SNRI) is allowed; Limited use of benzodiazepines (maximum of 10 mg/day diazepam equivalent).

Exclusion Criteria:

History of mania, hypomania, or bipolar disorder; Contraindications to the use of transcranial stimulation; Active suicidal ideation or suicide attempt in the last 4 weeks; Refractoriness to 3 or more antidepressant treatments; Pregnancy; Other psychiatric diagnoses (e.g., schizophrenia, substance dependence, major depressive disorder); Severe medical or neurological conditions; Anxiety or insomnia secondary to other medical or psychiatric conditions (e.g., hypothyroidism, anemia).

Individual participant data (IPD) that underlie the results reported in this article will be made available after deidentification, including study protocol and statistical analysis plan.

Beginning 6 months following publication, for up to 2 years.

Qualified researchers whose proposals are approved by the principal investigator will be granted access to deidentified individual participant data. Requests must include a clear scientific rationale and plan for data use. Data will be shared through secure electronic transfer upon agreement with data use terms.

None (Open Label)