The Efficacy of Photobiomodulation Therapy in Improving Cognitive Function and Reducing Depression and Anxiety in Patients with Mild-to-Moderate Dementia: A Double-Blinded Randomized Clinical Trial

Abstract

Background:

There is strong evidence supporting the effectiveness of photobiomodulation therapy (PBMT) in improving neuronal damage and enhancing neuropsychological activities. However, there is limited research on the effects of this method on cognitive function and mood disorders. This project aimed to evaluate the potential benefits of PBMT in improving cognitive status and mood disorders in patients with dementia.

Methods:

In this randomized, double-blinded, controlled trial, 30 patients with mild-to-moderate dementia participated. The patients were divided into two groups: the first group (n = 15) received standard treatment along with PBMT, whereas the second group (n = 15) received standard treatment along with the use of an off-device on the head. Cognitive function, anxiety, and depression levels were assessed before, immediately after treatment, and 1 month later.

Results:

The comparison of cognitive functional score at baseline, after completing the therapeutic regimen, as well as one later showed no difference between the two groups (Table 1). Similarly, the two groups had similar mean scores for depression and anxiety at baseline and after treatment interventions.

Table 1.

The Mean Change from the Baseline of the MMSE Test, Anxiety Scale, and Cognitive Scale Among the Mild-to-Moderate Patients in the Case and Control Group (at Baseline, After Treatment, and 1 Month After the Treatment Completion)

Characteristics	PBMT group (n = 15)	Control group (n = 15)	p value
Gender, %			1.000
Male	7 (46.7)	7 (46.7)
Female	8 (53.3)	8 (53.3)
Mean age, year	69.13 ± 2.89	70.12 ± 3.26	0.889
Educational level, %			0.546
Illiterate	6 (40.2)	5 (33.4)
Undergraduate	5 (33.4)	5 (33.4)
Diploma	3 (25.0)	3 (25.0)
Academic	1 (6.6)	2 (13.2)
Job status, %			0.459
Retired	3 (25.0)	3 (25.0)
Self-employed	5 (33.4)	3 (25.0)
Employed	2 (13.2)	2 (13.2)
Housekeeper	5 (33.4)	6 (40.2)
Worker	0 (0.0)	1 (6.6)

MMSE, Mini-Mental State Examination; PBMT, photobiomodulation therapy.

Conclusion:

The treatment likely has no significant impact on improving cognitive status or mood disorders in patients with mild-to-moderate dementia.

Keywords

cognitive function depression anxiety dementia photobiomodulation

Introduction

Dementia is a clinical syndrome characterized by significant cognitive impairment in one or more areas, including complex attention, executive function, learning and memory, language, perceptual-motor ability, and social cognition. This leads to disruption in daily activities and ultimately reduces the quality of life.¹ From a neuropathological point of view, dementia results in the loss of neurons and reduction of the volume of cortical areas, which can be measured using magnetic resonance imaging (MRI) through visual scales or volumetric techniques.^2,3 Currently, about 12 million people worldwide suffer from dementia, and this number is expected to reach 25 million by 2040.⁴ The usual management strategy for this disease is drug therapy,⁵ but there is uncertainty regarding its efficacy, safety, and higher rates of adverse effects.⁶ Recent efforts to develop a nonpharmacological approach for dementia patients are considered more favorable. Photobiomodulation (PBM) using laser or light-emitting diode (LED) has been used for wound healing and pain relief purposes.⁷ Recent studies have found that this method can restore damaged nerve cells in brain tissue.⁸ Transcranial PBM therapy (PBMT) using LED light sources has been used by various researchers to treat brain damage and psychiatric disorders such as depression, dementia, and Parkinson’s disease.^9–11 Pathophysiologically, transcranial PBMT has been associated with the stimulation of neurogenesis, as shown in some animal models.¹² There is also substantial evidence that this method increases brain-derived neurotrophic factor, heals brain lesions caused by stroke, and improves brain function in animals.^13,14 Recent studies show that PBMT reduces hippocampal neurodegeneration caused by water accumulation.¹⁵ Moreover, this method effectively increases cerebral blood flow and modulates the cognitive abilities of patients with dementia, thereby improving executive function in these patients.¹⁶

Given the rising global prevalence of dementia, it is important to consider noninvasive and nonpharmacological methods for improving the physiological and functional states related to this disorder. However, there have been few interventional studies conducted on human samples regarding the effectiveness of PBMT as a treatment method. Therefore, the present study aimed to investigate the effect of PBMT in reducing cognitive symptoms and mood disorders in patients with mild and moderate dementia.

Materials and Methods

Study population

A randomized, double-blinded controlled trial was conducted on 30 patients with mild-to-moderate dementia at Taleghani Hospital in Tehran in 2023. The study included patients over 65 years old who had been diagnosed with dementia for at least 2 years and were receiving standard medical treatment. Patients with a history of major psychiatric disorders, severe head trauma, claustrophobia, substance abuse, or those taking benzodiazepines were excluded from the study. In addition, individuals who had experienced significant changes in symptoms and/or medication regimen in the last 6 months were also excluded. Informed consent was obtained from all patients and their close relatives, and the study protocol was ethically approved by the ethics committee at Shahid Beheshti University of Medical Sciences. The clinical trial was registered under IRCT20220614055175N1 in the Iranian Registry of Clinical Trials (Registration date: 2022-12-12). This study was conducted by the Declaration of Helsinki and was approved by the ethical committee of Shahid Beheshti University of Medical Sciences, Tehran, Iran (Ethical code: IR.SBMU.MSP.REC.1401.349).

Study interventions

The patients were randomly assigned into two groups using a computerized random number table: the PBM group and the control group. Patients in the PBM group received PBM treatment three times a week for 2 weeks, with each session lasting 20 min. A new PBM system designed for transcranial PBM was used, which consisted of a helmet and a control device. The helmet was equipped with 12 visible LEDs (630 nm, 100 mW) and 12 infrared LEDs (850 nm, 100 mW). PBMT protocol parameters are all provided in Table 2 for easier recognition. As part of the initial assessment, we gathered baseline information on demographics, clinical symptoms, and disease duration from all subjects. Additionally, we conducted evaluations for dementia, depression, and anxiety. The state of dementia was determined using the Mini-Mental State Examination (MMSE), an 11-question measure that assesses orientation, registration, attention and calculation, recall, and language. Scores on this scale range from 0 to 30, and a score of 23 or lower suggests cognitive impairment. The validated Persian version of the MMSE questionnaire developed by Zohre Khodamoradi and colleagues was used.¹⁷

Table 2.

Photobiomodulation Therapy Protocol Parameters

Parameter	Specification
Device type	Custom-designed transcranial LED helmet
LED types	12 Red LEDs + 12 infrared LEDs
Wavelengths	Red: 630 nm; infrared: 850 nm
Power output per LED	100 mW
Total power output	2.4 W (24 LEDs × 100 mW)
Irradiated area	Approximately 250 cm² (helmet coverage of frontal, parietal, and temporal regions)
Irradiance (power density)	∼9.6 mW/cm² (assuming uniform distribution over 250 cm²)
Session duration	20 min (1200 sec) per session
Sessions per week	3 sessions
Total treatment duration	2 weeks (6 sessions total)
Energy per session	2.4W × 1200 s = 2880 J
Fluence (energy density)	2880 J ÷ 250 cm² ≈ 11.5 J/cm²
Mode of operation	Continuous wave, nonpulsed
Application sites	Full cranial coverage via helmet (frontal, parietal, and temporal lobes)
Distance from scalp	Direct contact via fitted helmet

LED, light-emitting diode.

Anxiety status was evaluated using the Hamilton Rating Scale for Anxiety (HRSA), a 14-scale clinician rating system that assesses the severity of biological and behavioral symptoms of anxiety. The scale includes a psychic subscale that addresses subjective cognitive and affective symptoms and a somatic component that focuses on physical symptoms such as autonomic arousal and respiratory, gastrointestinal, and cardiovascular symptoms.¹⁸

The status of depression was determined using the Geriatric Depression Scale (GDS) Long Form, a 30-item questionnaire where participants responded with “yes” or “no” based on how they felt over the past week. In 1986, a Short-Form GDS with 15 questions was developed. The questions were selected from the Long-Form GDS based on their strong correlation with depressive symptoms in validation studies. Out of the 15 items, 10 indicate the presence of depression when answered positively, whereas the rest indicate depression when answered negatively. Scores of 0–4 are considered normal, depending on age, education, and complaints; 5–8 indicate mild depression; 9–11 indicate moderate depression; and 12–15 indicate severe depression.¹⁹ These evaluations were conducted before treatment (in the first session) and were repeated after completing treatment, as well as 1 month later (Figs. 1 and 2).

FIG. 1.

Consort flowchart of the study.

FIG. 2.

Patient participating in the study.

Statistical analysis

The data were analyzed using SPSS software (version 23). The results were presented in two sections: descriptive and analytical. The descriptive section used mean and standard deviation for quantitative variables and number and percentage for qualitative variables. In the analytical section, we used an independent T test or Mann–Whitney U test to compare scaling scores between the two groups. We also used the Chi-Square test for comparing qualitative parameters and the repeated measure analysis of variance test to assess the trend of changes in study parameters between the groups. In all tests, the significance level was set at p < 0.05.

Results

The two groups scheduled for PBMT and the control group were similar in baseline characteristics, including gender, average age, educational level, and occupational status (Table 3). The comparison of cognitive functional scores at baseline, after completing the therapeutic regimen, and 1 month later showed no difference between the two groups (refer to Table 1). Similarly, the two groups had similar mean scores for depression and anxiety at baseline and after the treatment interventions (Table 1). Assessing the changes in cognition, depression, and anxiety scores from before the intervention to 1 month after showed no significant trend in either group. Additionally, the trend of the changes in the mentioned scores was not statistically different across the two PBMT and control groups (Fig. 3).

FIG. 3.

The trend of the changes in the scores of cognitive function (A), anxiety (B), and depression (C) among the mild-to-moderate patients in the case and control group.

Table 3.

Baseline Characteristics of Patients with Mild-to-Moderate Dementia Who Participated in This Study

Characteristics	PBMT group(n = 15)	Control group(n = 15)	p value
Cognitive scale (MMSE)
Before treatment	15.20 ± 3.58	16.46 ± 3.66	0.347
After treatment	15.33 ± 3.69	16.60 ± 3.58	0.349
One month later	15.20 ± 3.91	16.40 ± 3.64	0.392
p value	0.334	0.582
Anxiety Scale (HRSA)
Before treatment	19.66 ± 4.62	17.80 ± 4.16	0.255
After treatment	18.40 ± 6.20	17.53 ± 4.27	0.660
1 month later	18.93 ± 5.61	18.06 ± 3.91	0.628
	0.252	0.334
Cognitive scale (GDS)
Before treatment	10.00 ± 1.96	11.00 ± 1.96	0.174
After treatment	10.46 ± 2.23	11.06 ± 2.01	0.466
One month later	10.13 ± 2.85	11.33 ± 2.09	0.199
	0.207	0.685

GDS, Geriatric Depression Scale; HRSA, Hamilton Rating Scale for Anxiety; MMSE, Mini-Mental State Examination; PBMT, photobiomodulation therapy.

Discussion

This study aimed to investigate the impact of PBMT on reducing cognitive impairments, anxiety, and depression in patients with mild and moderate dementia. The results indicated that there was no significant difference in anxiety, depression, and cognitive symptoms between the groups before, after the intervention, and 1 month later. Additionally, there was no difference in the average scores within each group before treatment, after treatment, and during follow-up. Similar studies have been conducted globally in recent years. For instance, Stephan et al. conducted a study to explore the effectiveness of PBM treatment for moderate and advanced dementia or Alzheimer’s disease. Their study showed significant improvement in moderate and advanced dementia with three or four 8-min treatments over a 5–7-day period using ultra-pulse technology.²⁰ In a study conducted by Kheradmand et al. to investigate the effects of PBMT on the cognitive symptoms of patients with dementia, 32 patients with dementia were randomly divided into the PBMT and sham groups. The findings show that PBMT could be a promising treatment method and an aid to drug treatment in dementia patients.²¹ However, the results were not significant in some groups, which is consistent with the present study. Additionally, Schiffer et al. investigated the effect of PBM infrared light on the forehead of 10 patients with depression and anxiety. The results showed significant improvement and reduction of both depression and anxiety status in the treated group, with the greatest reduction occurring 2 weeks after intervention. Also, cerebral blood flow increased significantly.²² In a study conducted by Naeser et al., patients with a history of traumatic brain injury were treated with PBMT three times a week for 6 weeks. The study found that after 1 week, 1 month, and 2 months of LED treatment, patients showed significant improvement in their sleep and interpersonal relationships, as reported by both the family members and the individuals themselves.²³ In another study by Chao et al., the effects of PBMT on cognitive and behavioral performance, brain perfusion, and functional connectivity at rest in dementia patients were investigated. The results showed that the treatment was well tolerated by patients and did not cause any side effects. Additionally, the study indicated that PBMT has the potential to be an effective home treatment for people with dementia.²⁴ Further, a study by Berman and colleagues examined the potential effect of PBMT on dementia in Alzheimer’s patients. The results of this study suggested an improvement in executive function, including clock design, immediate recall, praxis memory, visual attention, and task switching, as well as EEG range and overall communication during the treatment process.^25,26

Despite the promising results from previous studies on PBMT in cognitive and mood disorders, our findings did not show significant improvements in cognitive performance, anxiety, or depression. Several factors may account for this discrepancy, which will be discussed below.

First, the relatively short treatment duration (2 weeks) and limited number of sessions (six sessions in total) may have been insufficient to produce measurable clinical changes. Previous studies with positive outcomes often employed longer treatment durations or higher session frequencies. Second, individual variability in patient characteristics—such as disease severity, duration of illness, and comorbidities—could have influenced responsiveness to PBMT. In addition, our sample size, while comparable with other pilot studies, may have lacked the power to detect subtle effects.

There were also some differences in PBMT protocols across studies that may also contribute to inconsistent results. For example, variation in energy density, irradiated anatomical regions, wavelength, and session frequency can all impact treatment outcomes. While our study used LEDs emitting at 630 nm and 850 nm, other studies have employed different ranges, such as 1060–1080 nm, which may penetrate deeper and interact with different cellular targets. Similarly, the choice of transcranial application sites (e.g., frontal cortex vs. parietal lobe) and irradiated surface area may influence PBMT’s efficacy on specific cognitive domains. These differences highlight the need for protocol standardization to improve comparability and replicability across trials.

The absence of significant clinical changes may also be related to the technical parameters of the PBMT device. While our device delivered a total power output of 2.4 W through a combination of red and infrared LEDs, other protocols reporting benefits have used higher fluence or power density. In particular, insufficient light penetration due to scalp hair, skull thickness, or suboptimal anatomical targeting might have attenuated the biological response. The duration of each session (20 min) and the treatment frequency may also not have allowed adequate cumulative energy delivery to trigger mitochondrial and neurotrophic effects. Therefore, the technical design of PBMT delivery—including light dispersion, uniformity of exposure, and fluence calibration—should be carefully considered in future trials. It is also essential to transparently report all PBMT parameters in clinical studies to enable cross-study comparisons and meta-analyses. Future research should adopt standardized reporting frameworks, including fluence, irradiance, pulse mode, energy per session, and anatomical targeting, as well as provide justification for parameter selection. Moreover, clinical trials should investigate dose–response relationships and optimal treatment windows, as current evidence suggests that PBMT’s therapeutic efficacy is highly sensitive to variations in these parameters.

Research has shown that this technique can lead to changes at the cellular and molecular levels, which may contribute to improvements in cognitive performance and mood symptoms. Cellular changes include increased adenosine triphosphate synthesis, higher levels of active oxygen species, and enhanced mitochondrial activation. Molecular changes, such as regulation of gene expression, have also been observed following the use of PBMT.^27–29

These cellular and molecular changes in the biological pathways related to neuropathic and psychopathic disorders may provide a basis for the improvement of cognitive and mood disorders in patients.³⁰ The study had some potential limitations. In this study, all patients were included through a standard questionnaire, interview, and examination. Genetic and laboratory tests, as well as brain imaging, were not performed to assess neurological or psychological impairments. The patients underwent light therapy for 2 weeks and were re-evaluated after 4 weeks; thus, the long-term effect was not evaluated. Additionally, the severity of the disease was not considered. The age requirement for the entry of patients over 65 years old was noted, and in some studies with younger samples, the results may differ. Genetic and laboratory testing, as well as brain imaging, were not conducted on the study patients. The patients received PBMT for 2 weeks and were evaluated for 4 weeks after the therapy. It is important to note that the duration of the light therapy and the time between the end of the treatment and the clinical assessment could lead to varying and unpredictable results. The study included patients over 65 years old who had been diagnosed with the disease for at least 2 years. However, it is worth considering that studies with younger participants may yield different results. In this research, MMSE, GDS, and HRSA tests were utilized. It is recommended to include ADAS-Cog tests and clock drawing tests for a more comprehensive evaluation. The study excluded patients who had experienced significant changes in their symptoms and medication regimen in the last 6 months. Using this treatment as an additional therapy is recommended because it has minimal side effects. Administering the treatment at home also helps in overcoming the challenges of transporting dementia patients to a clinic, making it easier for them to participate in research. In future studies, enhancing the sample size by including younger individuals, extending the treatment and follow-up periods, and using more comprehensive tools and paraclinical methods can help in obtaining more meaningful results. In addition, increasing the sample size will allow for the examination of treatment effects based on the severity of dementia and gender. Although this treatment has not shown any significant side effects, it is important to report even mild symptoms such as headaches or sweating.

Conclusions

According to our study, the use of therapeutic methods did not have a significant effect on cognitive function or improvement of anxiety and depression disorders. It seems that the protocol for using this method should be reconsidered, especially the wavelength used, the length of the treatment period, or the background conditions of the patients.

Authors’ Contributions

P.T.T. and A.K.: Supervisors. F.T.: Consulting supervisor. T.K.: Data collection. S.J., N.S., and A. K.: Writer.

Footnotes

Acknowledgments

The authors would like to acknowledge the support of Taleghani Hospital, Shahid Beheshti University of Medical Sciences (SBMU).

Author Disclosure Statement

The authors declare that they have no competing interests.

Funding Information

No funding was received for this article.

Ethics Approval and Consent to Participate

All procedures followed were under the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000. Informed consent was obtained from all patients to be included in the study. The clinical trial was registered under IRCT20220614055175N1 in the Iranian Registry of Clinical Trials (Registration date: 2022-12-12). This study was conducted by the Declaration of Helsinki and was approved by the ethical committee of Shahid Beheshti University of Medical Sciences, Tehran, Iran (Ethical code: IR.SBMU.MSP.REC.1401.349). Informed consent was obtained from all patients and their close relatives.

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