This study aims to evaluate the effectiveness of internet-based cognitive behavioral therapy (ICBT) combined with treatment as usual (TAU) for adults diagnosed with generalized anxiety disorder (GAD) or major depressive disorder (MDD) in Taiwan.

CBT is a proven treatment for anxiety and depression, but traditional face-to-face sessions require frequent clinic visits, which may be costly and time-consuming. ICBT delivers similar therapy content online, allowing participants to complete sessions at their own pace, reducing barriers such as travel and scheduling.

A total of 160 participants will be randomly assigned to receive either TAU alone or TAU plus an 8-week ICBT program delivered via a secure national research platform. The program includes 12 online modules covering cognitive restructuring, emotion regulation, and behavioral activation techniques. Participants will complete assessments before, during, and after the program, with follow-up at 3 months.

The results will help determine whether ICBT can improve symptoms, enhance treatment accessibility, and support the integration of digital mental health interventions into clinical practice in Taiwan.

This randomized controlled trial will assess the efficacy and feasibility of a locally adapted internet-based cognitive behavioral therapy (ICBT) program for patients with generalized anxiety disorder (GAD) or major depressive disorder (MDD) in Taiwan. The trial will be conducted at the Department of Psychiatry, National Taiwan University Hospital Hsin-Chu Branch, in collaboration with the National Health Research Institutes (NHRI).

A total of 160 eligible participants (aged 20-65 years) diagnosed with GAD or MDD will be recruited and randomly assigned to either the experimental group (TAU + ICBT) or the control group (TAU only), with 80 participants in each diagnostic category. The ICBT program lasts for 8 weeks and consists of 12 online modules, each released every 5 days, incorporating techniques such as cognitive restructuring, mindfulness, self-compassion, and behavioral activation. The control group will receive TAU and will be offered access to the ICBT program after study completion.

Assessments will be conducted at baseline, mid-intervention (week 5), post-intervention (week 9), and 3-month follow-up, using standardized self-report measures including GAD-7, PHQ-9, DASS-21, ISI, and other psychological well-being and user experience scales.

Primary outcomes are symptom reduction in anxiety (GAD-7) and depression (PHQ-9). Secondary outcomes include changes in psychological distress, insomnia severity, self-compassion, intolerance of uncertainty, and user satisfaction. Data will be analyzed using between-group comparisons and hierarchical linear modeling to evaluate both immediate and sustained intervention effects.

The study is expected to provide empirical evidence for the integration of digital mental health interventions into clinical practice, improve treatment accessibility, and support policy and service innovation in Taiwan.

Inclusion Criteria:

• Age between 20 and 65 years.
• Diagnosis of Generalized Anxiety Disorder (GAD) confirmed by a psychiatrist.
• Diagnosis of Major Depressive Disorder (MDD) confirmed by a psychiatrist, without acute suicidal risk (screened by PHQ-9 Item 9; score of 3 requires further clinical assessment to exclude active suicidal plan or recent self-harm).

Exclusion Criteria:

• For GAD ICBT participants

  • Current or past history of obsessive-compulsive disorder, panic disorder, bipolar disorder, eating disorder, schizophrenia, or substance abuse.
  • Severe depressive symptoms impairing daily functioning.
  • Current suicidal ideation.
  • Experiencing acute life stressors (e.g., domestic violence, ongoing treatment for serious physical illness).
  • Currently receiving psychological counseling or psychotherapy.
  • Other serious factors limiting participation (e.g., intellectual disability, significant cognitive impairment, severe vision or hearing impairment).

• For MDD ICBT participants

  • Diagnosis of bipolar disorder, eating disorder, schizophrenia, psychotic symptoms, or substance abuse.
  • Current suicidal ideation or recent self-harm (PHQ-9 Item 9 score of 3 triggers further assessment; exclusion if active suicidal plan or recent self-harm present).
  • Experiencing acute life stressors (e.g., domestic violence, ongoing treatment for serious physical illness).
  • Currently receiving psychological counseling or psychotherapy.
  • Other serious factors limiting participation (e.g., intellectual disability, significant cognitive impairment, severe vision or hearing impairment).