Efficacy of Transcranial Direct Current Stimulation (tDCS) in the Treatment of Adult Attention-Deficit/Hyperactivity Disorder (ADHD)

Attention-Deficit/Hyperactivity Disorder (ADHD) is a neurodevelopmental disorder characterized by attentional difficulties and/or hyperactivity-impulsivity (American Psychiatric Association, 2013). Its treatment is primarily based on a multimodal approach, with first-line pharmacological management using methylphenidate (Ritalin®, Medikinet®, etc.).

However, given the limitations of pharmacological treatments (side effects, contraindications, and risks of misuse), alternative approaches such as transcranial direct current stimulation (tDCS) are generating increasing interest.

tDCS is a non-invasive, safe, and low-cost neuromodulation technique that delivers a low-intensity electrical current through electrodes placed on the scalp. It is well tolerated, with mild and transient adverse effects (tingling sensations, local skin redness, mild fatigue), making it a particularly safe approach. Its low cost and ease of use allow for broad accessibility, including in resource-limited healthcare settings.

In ADHD, tDCS targets the left dorsolateral prefrontal cortex, a key region involved in attention and executive functions. Early studies have reported encouraging results in terms of both efficacy and tolerability, particularly when combined with psychotherapeutic interventions.

The aim of this study is to evaluate the efficacy of tDCS in patients with ADHD.

The findings will support the potential future integration of tDCS into the management of ADHD resistant to conventional treatments.

Inclusion criteria

• Adult patient aged 18 to 60 years inclusive
• Patient diagnosed with Attention-Deficit/Hyperactivity Disorder (ADHD), combined or predominantly inattentive presentation, previously established by a healthcare professional
• Patients must be registered in the active caseload of the Adult Neurodevelopmental Disorders Unit (STNDA)
• Stable psychotropic medication regimen for at least four weeks prior to inclusion, in terms of both molecule and dosage, particularly for methylphenidate, or no current psychotropic treatment. Medication must remain unchanged throughout study participation, unless medically justified changes are required
• Patient with a cognitive status deemed sufficient by the unit's referring psychiatrist to ensure appropriate completion of the scales and tests included in the protocol
• Free, informed, and written consent

Exclusion criteria

•General condition impairment (severe fatigue or marked weakness, convalescence after an acute illness or surgery, or recent alcohol consumption)

Psychiatric and neurological disorders

• Diagnosis of Autism Spectrum Disorder (ASD)
• Diagnosis of personality disorder (Cluster A, B, C, or other), according to DSM-5-TR
• Diagnosis of schizophrenia spectrum disorder or other psychotic disorders according to DSM-5-TR
• Diagnosis of bipolar disorder with manic episode or history of manic episodes according to DSM-5-TR
• Confirmed neurological disorder
• Epilepsy or history of epileptic seizures

Medical comorbidities

• Patient with known or suspected cardiac disease
• Patient with severe pulmonary disease
• Patient with cerebrovascular disease (e.g., stroke)

Dermatological and surgical contraindications

• Patient with scalp lesions, open wounds, or skin conditions (severe acne, herpes, burns, skin fissures)
• Patient with severe dermatitis, oozing eczema, or fragile scalp
• Patient with major surgical scars
• Patient with recent craniotomy

Implantable devices and materials

• Patient with a pacemaker or intracranial electrodes, presence of intracranial metal, or skull defects (e.g., post-craniectomy or trepanation without reconstruction)

Other criteria:

• Simultaneous participation in another non-pharmacological intervention provided in the STNDA day hospital (e.g., psychoeducation, cognitive remediation, body expression therapy, emotional regulation training)
• Patient with non-pathological ASRS screening scores (fewer than 4 of the first 6 items rated "Very often")
• Insufficient proficiency in the French language
• Patient under legal guardianship, curatorship, or judicial protection
• Pregnant or breastfeeding patient (based on clinical interview)