To explore the efficacy of dCBT-I therapy for chronic insomnia among breast cancer survivors in China, we propose to conduct a randomized, parallel controlled clinical study in breast cancer survivors using a smartphone Chinese application (app) "resleep". Breast cancer survivors with chronic insomnia were recruited from our Breast Disease Center and externally, with the waiting group as a parallel control and the dCBT-I treatment group as an intervention group, in a 1:1 sample size. Intervention group (dCBT-I treatment group) will receive full self-help dCBT-I administered by smartphone APP for 6 weeks. The control group (waiting for treatment group) will not receive any additional interventions based on the original conventional treatment and will be followed up as planned, waiting for treatment.At the end of the 3-month follow-up, the decision to receive treatment was made according to the patient's wishes. The primary endpoint was the insomnia severity index (ISI) at the end of treatment and at 3 months of treatment.

Inclusion Criteria:

1. Age ≥ 18 years.
2. Breast cancer diagnosed within 5 years
3. Stable disease at the end of acute treatment (surgery, radiotherapy, chemotherapy) while meeting: ≥ 1 month after surgery, ≥ 3 months after the end of last chemotherapy, and ≥ 3 months after the end of last radiotherapy if radiotherapy is required.
4. Satisfy the diagnostic criteria for chronic insomnia disorder according to the (International Classification of Sleep Disorders-the Third Edition, ICSD-3)[ and Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5): problem with falling asleep or maintaining sleep for ≥3 months (≥3 times per week) with impaired daytime functioning, despite the availability of sleep opportunities.
5. ISI score ≥12.
6. Other sleep or psychiatric disorders, if present, must be stable and require no medication.
7. Be proficient in the use of a cell phone application, and be comfortable reading, filling out the electronic questionnaire, communicating, and fully understanding the content.
8. Sign the informed consent form. -

Exclusion Criteria:

1. New breast cancer progression, recurrence, or metastasis within 3 months, requiring new radiotherapy or immunotherapy regimen
2. Expected survival <12 months due to all causes
3. Presence of any of the following conditions: Concurrent active cancer or malignancy that is being treated other than breast cancer, shift work, alcohol abuse, substance abuse, significant suicidal ideation, bipolar disorder, aggressive behavior, mania, schizophrenia.
4. Presence of a diagnosed significant physical illness that interferes with sleep, such as cranial disease or trauma, cancer pain, unstable angina, uncontrolled cardiac insufficiency and severe respiratory distress due to various causes, etc.
5. Current or previous treatment with cognitive behavior therapy for insomnia (CBT-I).
6. Not signed informed consent.](streamdown:incomplete-link)