This randomized clinical trial is focused on perimenopausal women who have difficulty sleeping. It will randomize digital cognitive behavioral therapy for insomnia (dCBT-I) or a sleep hygiene intervention (SHI). After treatment, participants will be assessed every 3-months over a 2-year period.

The two main questions the study aims to answer are:

1. Do participants receiving dCBT-I experience less severe depressive symptoms compared with sleep hygiene (SH) over 2 years of study participation?
2. Are the effects of dCBT-I on depressive symptom severity mediated by an improvement in insomnia symptoms?

Insomnia is a common problem for women in perimenopause. Previous research found that insomnia predicts future development of depression and suggests that treating insomnia can lead to improvement in mood. This study will investigate the long-term effects of treating insomnia with two different interventions on depression among perimenopausal individuals. The two interventions are, digital cognitive behavioral therapy for insomnia (dCBT-I), which has been proven effective, and sleep hygiene intervetion (SHI), which is in common use in general practice.

Participants will be screened for eligibility. Those eligible will be randomized to one of the two treatment arms (dCBT-I or SHI) and complete assessments at 3-month intervals across a 2-year period. Assessments will include questionnaires, clinical interviews, and using a wearable device. All assessments will be done remotely.

Aim 1: To determine if dCBT-I in the menopause transition prospectively prevents depressive symptoms and improves menopause-specific quality of life.

Aim 2: To determine whether the effect of dCBT-I on depressive symptoms is mediated through improving insomnia symptom severity (primary) and secondarily, reducing wakefulness after sleep onset in the menopause transition.

The study will also explore pathways linking dCBT-I and prevention of depressive symptoms.

Inclusion Criteria:

1. At least 40 years old and in the perimenopause,
2. Willingness to participate in a digital research protocol,
3. Current moderate to severe insomnia symptoms that started or worsened in association with perimenopause,
4. English fluency.

Exclusion Criteria:

1. Current major depressive disorder
2. Existing diagnosis of a sleep disorder other than insomnia
3. Experiencing excessive daytime sleepiness
4. Having received CBT-I in the preceding 6 months
5. Severe psychiatric or medical conditions or medications that could compromise safe participation in the study or interfere with the scientific aims
6. Hysterectomy and/or bilateral ovariectomy or current hormonal therapy,
7. Night shift worker