ANZCTR - Registration

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Trial registered on ANZCTR

Registration number

ACTRN12626000932369

Ethics application status

Approved

Date submitted

15/07/2026

Date registered

29/07/2026

Date last updated

29/07/2026

Date data sharing statement initially provided

29/07/2026

Type of registration

Retrospectively registered

Titles & IDs

Public title

Effect of a circadian-informed light intervention on depression in individuals taking an antidepressant

Scientific title

The effect of a circadian-informed light intervention on improving depressive symptoms in individuals taking selective serotonin reuptake inhibitors (SSRIs)

Additional trial identifiers [1]

Nil

Universal Trial Number (UTN)

Trial acronym

Related trial records

Health condition

Health condition(s) studied:

depression

Condition category

Condition code

Mental Health

Depression

Intervention/exposure

Study type

Interventional

Description of the intervention or exposure

Participants allocated to the intervention group replaced their usual home lighting with pre-configured low-intensity warm smart LED bulbs (6.00 lux, 2452 K), used in place of their regular lighting in main living areas after sunset and before bedtime, for a period of four weeks. They were also asked to seek bright outdoor light during the day and reduce evening screen use before bed. This design aimed to reduce the disruptive effects of modern lighting environments (e.g., dim light during the day and bright light in the evening) on the circadian system (known as the 'body clock') and subsequent mood.

Participants received the pre-configured smart lighting equipment and a printed psychoeducation handout outlining the intervention instructions during an in-person visit at the laboratory, The intervention was then self-administered by participants in their own homes each evening over the four week period.

Adherence to the intervention was assessed objectively using a wearable light monitoring device.

Intervention code [1]

Lifestyle

Description of the comparator or control

Participants in this group continued their usual evening home lighting and routines for four weeks. No lighting equipment, psychoeducation materials, or behavioural instructions were provided.

Participants completed the same at-home monitoring of sleep, mood, and light as the intervention group.

Control group

Active

Outcomes

Primary outcome [1]

Depressive symptom severity

Timepoint [1]

At baseline and each week of the intervention period (Week 1, Week 2, Week 3, Week 4)

Secondary outcome [1]

Insomnia symptom severity

Timepoint [1]

At baseline and each week of the intervention period (Week 1, Week 2, Week 3, Week 4)

Secondary outcome [2]

Amount of evening light exposure

Timepoint [2]

Baseline & intervention period (Weeks 1-4), measured every 2 minutes across the 24-hour day

Secondary outcome [3]

Amount of morning light exposure

Timepoint [3]

Baseline & intervention period (Weeks 1-4), measured every 2 minutes across the 24-hour day

Secondary outcome [4]

Time spent in bright light across the day

Timepoint [4]

Baseline & intervention period (Weeks 1-4), measured every 2 minutes across the 24-hour day

Eligibility

Key inclusion criteria

- A Beck Depression Inventory-II (BDI-II) score of 20 or more, indicating at least moderate depressive symptom severity.
- Regular use of a SSRI for a minimum of 8 weeks prior to enrolment.

Minimum age

18 Years

Maximum age

40 Years

Sex

Both males and females

Healthy volunteers

Key exclusion criteria

- Major medical conditions
- Current use of medications other than their antidepressant which may affect sleep or circadian rhythms
- Recent shit-work or travel across time-zones
- A history of psychosis or a family history of bipolar disorder
- Current substance use disorder.
- High risk of suicide

Study design

Purpose of the study

Treatment

Allocation to intervention

Randomised controlled trial

Procedure for enrolling a subject and allocating the treatment (allocation concealment procedures)

Allocation was not concealed.

Methods used to generate the sequence in which subjects will be randomised (sequence generation)

Randomisation was computer generated and stratified by sex and BDI-II (five bands spanning total scores of 20-36+).

Masking / blinding

Open (masking not used)

Who is / are masked / blinded?

Intervention assignment

Parallel

Other design features

Phase

Not Applicable

Type of endpoint/s

Efficacy

Statistical methods / analysis

Recruitment

Recruitment status

Completed

Date of first participant enrolment

Anticipated

Actual

22/08/2022

Date of last participant enrolment

Anticipated

Actual

13/09/2023

Date of last data collection

Anticipated

Actual

18/10/2023

Sample size

Target

Accrual to date

Final

Recruitment in Australia

Recruitment state(s)

VIC

Funding & Sponsors

Funding source category [1]

Other

Name [1]

Beacon Lighting

Address [1]

Country [1]

Australia

Primary sponsor type

University

Name

Monash University

Address

Country

Australia

Secondary sponsor category [1]

None

Name [1]

Address [1]

Country [1]

Ethics approval

Ethics application status

Approved

Ethics committee name [1]

Monash University Human Research Ethics Committee

Ethics committee address [1]

https://www.monash.edu/researchoffice/ethics

Ethics committee country [1]

Australia

Date submitted for ethics approval [1]

14/10/2019

Approval date [1]

05/12/2019

Ethics approval number [1]

Summary

Brief summary

By the year 2030, depression is projected to the leading cause of disease burden worldwide. Although 1 in 10 Australians are currently taking an antidepressant medication, as many as 45% of patients will not respond to the beneficial effects of antidepressants. Depression is commonly associated with disrupted sleep and circadian ('body clock') rhythms, which rely on light from the environment. Previous research has found that there are individual differences in the sensitivity towards light, especially in patients taking Selective Serotonin Reuptake Inhibitors (SSRIs; the most common antidepressant medication). The increase in the effect of light from antidepressant medication on patients with depression may depend on the individual’s light exposure patterns. Individuals who tend to expose themselves to irregular light patterns especially at night, report poorer responses to SSRI treatment and increased depression during SSRI treatment compared to those that tend to seek bright light during the morning. Therefore, reducing evening home lighting and encouraging increased daylight exposure may enhance antidepressant efficacy.

We aimed to investigate the ability of a circadian-informed light intervention to increase the beneficial effects of light and reduce the adverse effects of light on depressive symptoms and insomnia symptoms for individuals taking an SSRI.

Trial website

Trial related presentations / publications

Public notes

Contacts

Principal investigator

Name

Prof Sean Cain

Address

Flinders Health and Medical Research Institute, College of Medicine and Public Health, 5 Laffer Drive Bedford Park SA 5062

Country

Australia

Phone

+61 08 8432 4242

Fax

[email protected]

Contact person for public queries

Name

Rebecca Fitton

Address

Turner Institute for Brain and Mental Health, School of Psychological Sciences, Monash University, 18 Innovation Walk, Clayton, VIC, 3800

Country

Australia

Phone

+61 3 9905 4098

Fax

[email protected]

Contact person for scientific queries

Name

Sean Cain

Address

Flinders Health and Medical Research Institute, College of Medicine and Public Health, 5 Laffer Drive Bedford Park SA 5062

Country

Australia

Phone

+61 08 8432 4242

Fax

[email protected]

Data sharing statement

Will the study consider sharing individual participant data?

No
No IPD sharing reason/comment: We do not currently have ethical approval for sharing this kind of data.

What supporting documents are/will be available?

No Supporting Document Provided

Results publications and other study-related documents

Documents added manually

No documents have been uploaded by study researchers.

Documents added automatically

No additional documents have been identified.

Trial Review

Documents added manually

Documents added automatically