Effectiveness of Light Therapy Across Seasons

NCT07599124 | Completed

• 1 other identifier: ILB/2020038
• Study Type: observational
• Target: 212
• Locations: 1 country
• Sites: 1

Brief Summary

This study investigates whether the antidepressant effects of bright light therapy (BLT) differ between the spring/summer season and the autumn/winter season in adults with depressive disorders. While BLT is an established treatment for seasonal affective disorder, increasing evidence suggests it may also be effective for non-seasonal depression. However, it remains unclear whether its effectiveness depends on seasonal variation in natural daylight exposure. In this prospective study conducted in a routine clinical care setting, patients referred for depressive symptoms and a score of \> 6 on the Quick Inventory of Depressive Symptomatology-Self-Report (QIDS-SR) receive BLT in a structured "Light Café" environment. Participants undergo daily morning light therapy sessions (30 minutes at 10,000 lux) for at least one week, with possible extension up to three weeks based on treatment response. A delayed-start design is used, where a subset of participants begins treatment two weeks later, allowing comparison with the natural course of depressive symptoms. Depressive symptoms are assessed using the QIDS-SR at baseline, during treatment, and at follow-up (6 weeks and 3 months post-treatment). Sleep quality, chronotype, circadian timing, and side effects are also measured. The primary objective is to compare the effectiveness of BLT across seasons. Secondary objectives include evaluating the persistence of treatment effects, assessing the change in sleep quality and day-to-day sleep-wake pattern, and exploring whether outcomes vary by chronotype, circadian phase, and patient characteristics. This study aims to inform whether BLT should be considered a year-round treatment option for depressive disorders and to better understand factors influencing individual treatment response.

Conditions

Depression; Unipolar Depression; Bipolar Depression Depressed Phase

Keywords

Depression; Bright Light Therapy; Chronotherapy; Sleep

Outcome Measures

Primary Outcomes (1)

• Change in depressive symptom severity (QIDS-SR)

  Depressive symptom severity is assessed using the Quick Inventory of Depressive Symptomatology - Self-Report (QIDS-SR), a validated 16-item questionnaire with total scores ranging from 0 to 27 (higher scores indicating greater symptom severity). The primary outcome is the change in QIDS-SR score from baseline (pre-treatment) to end of light therapy. The analysis compares changes between participants treated in the spring/summer season and those treated in the autumn/winter season, while accounting for the delayed-start control condition.

  Baseline to end of treatment (approximately 1-3 weeks after initiation of light therapy)

Secondary Outcomes (5)

• Sustained change in depressive symptoms (QIDS-SR follow-up)

  End of treatment to 6 weeks and 3 months post-treatment

• Change in sleep quality (PSQI)

  Baseline to 6 weeks and 3 months post-treatment

• Chronotype (MEQ)

  Baseline (chronotype assessment), end of treatment (1-3 weeks after initiation of light therapy), 6 weeks post-treatment, and 3 months post-treatment

• Adverse Events and Side Effects

  At the end of each treatment week, up to 3 weeks

• Change in Sleep-Wake Pattern during treatment

  Twice weekly during treatment, up to 3 weeks

Study Arms (2)

Spring/summer

Patients with a depression who received bright light therapy as part of routine clinical care. For the purpose of the analyses, participants were categorized based on the season of treatment initiation, with this cohort including those who started treatment during the spring and summer seasons.

Device: Bright Light Therapy

Autumn/winter

Patients with a depression who received bright light therapy as part of routine clinical care. For the purpose of the analyses, participants were categorized based on the season of treatment initiation, with this cohort including those who started treatment during the autumn and winter seasons.

Device: Bright Light Therapy

Interventions

Bright Light Therapy DEVICE

Bright Light Therapy (BLT) will be administered according to Dutch depression guidelines, using Innolux LED light lamp (3800K, 10,000 lux). BLT will be given for one work week (Mon-Fri), 7:30-10:30 AM, 30 mins/session. Patients can have breakfast, read, or use devices. Treatment effectiveness will be evaluated using Self-Rated Quick Inventory of Depressive Symptoms (QIDS-SR). If remission is achieved (QIDS-SR \< 6), no additional treatment is given. If response is insufficient (QIDS-SR ≥ 6), 5 more sessions will be added in the following week, with maximum two extensions (1-3 weeks total).

Autumn/winter; Spring/summer

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)
• Sampling Method: Non-Probability Sample

Study Population

The study population consists of patients with depression who are referred for treatment of depressive symptoms within a mental health care setting (GGzE, Eindhoven, The Netherlands), where bright light therapy is offered in a structured "Light Café" environment as part of routine clinical care.

You may qualify if:

• Adults aged 18 years or older
• Diagnosis of a depressive disorder (unipolar or bipolar), including both seasonal and non-seasonal depression
• Currently indicated for bright light therapy
• QIDS-SR score ≥ 6 at baseline
• Able to provide informed consent
• Sufficient proficiency in Dutch or English to complete questionnaires

You may not qualify if:

• Current (hypo)manic or mixed episode
• Current psychotic episode
• Severe suicidal ideation requiring immediate intervention
• Diagnosis of dementia
• QIDS-SR score ≤ 5 at baseline
• Age \< 18 years
• Inability to provide informed consent
• Insufficient language proficiency to complete study questionnaires
• Initiation, dose change, or switch of antidepressant medication within 3 weeks before or during light therapy
• Long-term use of agomelatine
• Relative Contraindications (require consultation with treating physician before participation):
• Pregnancy (first trimester)
• Diabetes or other systemic vascular diseases
• Eye conditions associated with increased light sensitivity
• Epilepsy

Sponsors & Collaborators

• Geestelijke Gezondheidszorg Eindhoven (GGzE): lead

Study Sites (1)

GGzE

Eindhoven, 5626ND, Netherlands

Location

MeSH Terms

Conditions

Depression; Depressive Disorder

Interventions

Ultraviolet Therapy

Condition Hierarchy (Ancestors)

Behavioral Symptoms; Behavior; Mood Disorders; Mental Disorders

Intervention Hierarchy (Ancestors)

Phototherapy; Therapeutics

Study Design

• Study Type: observational
• Observational Model: COHORT
• Time Perspective: RETROSPECTIVE
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Senior researcher

Study Record Dates

• First Submitted: May 12, 2026
• First Posted: May 20, 2026
• Study Start: January 1, 2021
• Primary Completion: October 7, 2022
• Study Completion: December 23, 2022
• Last Updated: May 20, 2026

Record last verified: 2026-05

Data Sharing

• IPD Sharing: Will not share

Locations

NL (1)