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ABSTRACT
Introduction
Despite the growing number of different therapeutic options, treatment of depression is still a challenge. A broader perspective reveals the benefits of bright light therapy (BLT). It stimulates intrinsically photosensitive retinal ganglion cells, which induces a complex cascade of events, including alterations in melatonergic, neurotrophic, GABAergic, glutamatergic, noradrenergic, serotonergic systems, and HPA axis, suggesting that BLT effects expand beyond the circadian pacemaker.
Areas covered
In this review, the authors present and discuss recent data of BLT in major depressive disorder, non-seasonal depression, bipolar depression or depressive phase of bipolar disorder, and seasonal affective disorder, as well as in treatment-resistant depression (TRD). The authors further highlight BLT effects in various depressive disorders compared to placebo and report data from several studies suggesting a response to BLT in TRD. Also, the authors report data showing that BLT can be used both as a monotherapy or in combination with other pharmacological treatments.
Expert opinion
BLT is an easy-to-use and low-budget therapy with good tolerability. Future studies should focus on clinical and biological predictors of response to BLT, on defining specific populations which may benefit from BLT and establishing treatment protocols regarding timing, frequency, and duration of BLT.
Article highlights
The current knowledge on the effects and administration of BLT in different forms of depression (MDD, SAD, depressive episode of BD and in TRD) is described.
Effects of BLT expand beyond the circadian pacemaker and are achieved via intrinsically photosensitive retinal ganglion cells.
The BLT mechanism of action may include melatonergic, neurotrophic, GABAergic, glutamatergic, noradrenergic, serotonergic and orexinergic systems, HPA axis, and retina-ventral lateral geniculate nucleus and intergeniculate leaflet/lateral habenula pathway.
BLT has a wide availability, low costs, convenient use and a good tolerability with usually mild and short-lived side effects.
BLT can be used both as a monotherapy or in combination with other pharmacological treatments.
Abbreviations
| 5-HTT | = | 5-hydroxytriptamine or serotonin transporter |
| AA-NAT | = | N-acetyltransferase |
| AD | = | Alzheimer’s disease |
| ADs | = | antidepressants |
| aMT6s | = | 6-sulfatoxymelatonin |
| BD | = | bipolar disorder |
| BDI | = | Beck Depression Inventory |
| BDNF | = | brain derived neurotrophic factor |
| BLT | = | bright light therapy |
| CRH | = | corticotrophin-releasing hormone |
| DMLO | = | dim light melatonin onset |
| ECT | = | electroconvulsive therapy |
| EDI | = | equivalent of daytime illuminance |
| EMA | = | European Medicines Agency |
| HAMD-17 | = | Hamilton Rating Scale for depression |
| HPA | = | hypothalamic-pituitary-adrenal |
| IGL | = | intergeniculate leaflet |
| ipRGCs | = | intrinsically photosensitive retinal ganglion cells |
| MADRS | = | Montgomery–Åsberg Depression Rating Scale |
| MAO-A | = | monoamine oxidase type A |
| MDD | = | major depressive disorder |
| LHb | = | lateral habenula |
| LT | = | light therapy |
| PD | = | Parkinson’s disease |
| PET | = | positron emission tomography |
| PHb | = | perihabenular nucleus |
| PMDD | = | premenstrual dysphoric disorder |
| PLR | = | pupillary light reflex |
| POAG | = | primary narrow-angle glaucoma |
| PRC | = | Phase response curve |
| PVN | = | paraventricular nucleus |
| RCT | = | randomized clinical trial |
| RGCs | = | retinal ganglion cells |
| rTMS | = | repetitive transcranial magnetic stimulation |
| SAD | = | seasonal affective disorder |
| SCN | = | suprachiasmatic nucleus |
| SNRIs | = | serotonin and norepinephrine reuptake inhibitors |
| SSRIs | = | selective serotonin reuptake inhibitors |
| TMS | = | transcranial magnetic stimulation |
| TRD | = | treatment-resistant depression |
| vLGN | = | ventral lateral geniculate nucleus |
| VTA | = | ventral tegmental area. |
Declaration of interest
The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.
Reviewer disclosures
Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.