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. 2024 Jan 19;14(1):112. doi: 10.3390/jpm14010112

Table 2.

Summary of clinical trials using photobiomodulation to treat the symptoms of Parkinson’s disease.

Study Participants Design PBM Parameters Outcomes
TRANSCRANIAL
Santos et al., 2019 [169] Idiopathic Parkinson’s disease;
H & Y stage 1–2;
No severe dyskinesis;
20 males; 15 females.		 RCT;
Sham (low dose) (n = 18)/PBM (n = 17).		 670 nm LED;
Transcranial;
60 mW/cm2 for 60 s alternating between left and right temples with 30 s rest between six treatments;
Twice per week for 9 weeks (18 treatments);
“sham” received 5 s treatment.		 Improved fast rhythm 10-metre walk test;
No other significant improvements.
Hamilton et al., 2019 [170] Idiopathic Parkinson’s disease. Case studies of three patients;
No placebo group.		 home-made PBM devices;
Transcranial.
670 nm + 850 nm or 810 nm LED strips;
30 min once per day
OR
20 min twice per day.		 A variety of self-reported improvements including motor (gait, tremor, fine motor skills and writing) and non-motor (sleeping, swallowing, sense of smell, speech, self-esteem and social interactions).
Hamilton et al., 2019 [171] Idiopathic Parkinson’s disease. Case studies of six patients
(two repeated from previous report) [170];
No placebo group.		 Variety of PBM devices;
Transcranial + intranasal.
Home-made device with 670 nm + 850 nm or 810 nm;
20 min or 30 min, once or twice per day
OR
Manufactured device with 670 nm + 810 nm LEDs;
20 min once or twice daily
OR
Intranasal device 660 nm;
20 min per day;
Ongoing treatment up to 24 months.		 A variety of self-reported improvements including motor (gait, tremor, rigidity, fine motor skills and writing) and non-motor (sleeping, swallowing, sweating, sense of smell, speech, self-esteem, social interactions and constipation).
Berman and Nichols 2019 [172] NR Case study;
Two participants;
No placebo group.		 1068 nm LED;
Transcranial;
2.6 mW/cm2 for 5 min;
Twice daily for 28 days.		 Improved clock drawing.
Tamae et al., 2020 [173] Idiopathic Parkinson’s disease;
Ages 30 to 80 years;
H & Y stage 1.5–2;
Muscle pain and stiffness.		 Parallel group trial;
Vacuum therapy (n = 6)/PBM (n = 6)/vacuum therapy + PBM (n = 6);
No placebo group.		 670 nm + 808 nm laser;
Cervical to lumbar spine + dorsal trunk + forearms and palm;
Power NR; time applied NR;
Two PBM treatments per week for 3 weeks (six treatments).		 Combined vacuum and PBM gave more pain relief (VAS) than either single treatment.
Liebert et al., 2019 [174] Idiopathic Parkinson’s disease;
Seven females; five males;
Aged between 60 and 80 years.		 Waitlist design;
Immediate treatment (n = 6)/waitlist (n = 6);
No placebo group.		 904 nm laser;
Abdominal;
30 mW/cm2 for 60 s on 9 points of abdomen + 1 point of neck;
PLUS
810 nm LED;
Transcranial;
100 mW/cm2 and 75 mW/cm2 for 20 min;
PLUS
810 nm LED;
Intranasal;
25 mW/cm2 for 25 min;
All 3 times per week for 4 weeks, then 2 times per week for 4 weeks then 1 time per week for 4 weeks, then 3 times per week for up to 1 year.		 Improvements in a range of motor (including gait, balance and fine motor skills) and cognitive outcome measures at both 12 weeks and 1 year;
Measurable Hawthorne effect, with outcome measures further improved on treatment.
Bullock-Saxton et al., 2019 [176] Idiopathic Parkinson’s disease. RCT;
Placebo (n = 10)/PBM (n = 10).		 904 nm laser;
Transcranial;
60 mW for 33 s;
PLUS
Intraoral;
60 mW for 33 s;
Three PBM treatments per week for 4 weeks;
4 weeks no treatment;
One PBM treatment per week for 4 weeks.		 No significant changes but indications of positive effects for fine motor skills and dynamic balance.
Hong et al., 2021 [177] Idiopathic Parkinson’s disease;
8 females; 12 males;
Aged 30 to 80 years;
H & Y stage 2–3.		 Case series (n = 18);
Combined therapy (PBM + h2 water);
No placebo group.		 940 nm LED;
Neck;
6 mW/cm2 for 30 min for 5 consecutive days.		 Improved UPDRS scores.
Liebert et al., 2022 [188] Idiopathic Parkinson’s disease;
Seven males;
Aged between 60 and 80 years.		 Case series (n = 7);
No placebo group.		 904 nm laser;
Abdominal;
30 mW/cm2 for 120 s on 9 points of abdomen + 1 point of neck;
For 12 weeks.		 Improvements in a range of motor (including gait, balance and fine motor skills) and cognitive outcome measures at both 12 weeks and 1 year.
Bicknell et al., 2022 [189]

Further results of Liebert et al.’s study [174]		 Idiopathic Parkinson’s disease;
Seven females; five males;
Aged between 60 and 80 years.		 Waitlist design;
Immediate treatment (n = 6)/waitlist (n = 6);
No placebo group.		 904 nm laser;
Abdominal;
30 mW/cm2 for 60 s on 9 points of abdomen + 1 point of neck;
PLUS
810 nm LED;
Transcranial;
100 mW/cm2 and 75 mW/cm2 for 20 min;
PLUS
810 nm LED;
Intranasal;
25 mW/cm2 for 25 min;
All 3 times per week for 4 weeks, then 2 times per week for 4 weeks, then 1 time per week for 4 weeks, then 3 times per week for up to 1 year.		 Changes to the microbiome following PBM.
Peci et al., 2023 [178] Idiopathic Parkinson’s disease;
13 females; 25 males;
Aged 60 to 75 years.		 Parallel group trial;
Physiotherapy (n = 26)/physiotherapy + PBM (n = 12);
No placebo group.		 810 nm LED array (256);
Transcranial;
24 mW/cm2 for 18 min, twice per week for 4 weeks.		 Combination of PBM and physiotherapy superior to physiotherapy alone for motor UPDRS scores.
Liebert et al., 2023 [175]
3-year follow-up of Liebert et al.’s 2019 study [174]		 Idiopathic Parkinson’s disease;
Seven females; five males;
Aged between 60 and 80 years.		 Waitlist design;
PBM treatment (n = 6)/no treatment (n = 2);
No placebo group.		 904 nm laser;
Abdominal;
30 mW/cm2 for 60 s on 9 points of abdomen + 1 point of neck;
PLUS
A variety of transcranial PBM devices.		 Mobility and cognition outcomes continued to improve up to 2 years and did not decline at 3 years if PBM was maintained; no outcome measure declined to below pre-treatment (3 years previous) if PBM had continued.
Herkes et al., 2023 [180] Idiopathic Parkinson’s disease;
20 females; 20 males;
Aged 60 to 80 years.		 Parallel randomised feasibility trial;
Placebo (n = 20)/PBM (n = 20).		 635 nm + 810 nm LED (20 + 20);
Transcranial;
27 mW (635 nm) for 12 min then
52 mW (810 nm) for 12 min;
Once per day, 6 days per week for 12 weeks;
Placebo group switched to PBM after 12 weeks.		 Safe and feasible treatment;
No significant difference for MDS-UPDRS-III scores between groups at 12 weeks;
Placebo group continued to improve after PBM treatment.
McGee et al., 2023 [181]
Further results of Herkes et al.’s study [180]		 Idiopathic Parkinson’s disease;
20 females; 20 males;
Aged 60 to 80 years.		 Parallel randomised feasibility trial;
Placebo (n = 20)/PBM (n = 20).		 635 nm + 810 nm LED (20 + 20);
Transcranial;
27 mW (635 nm) for 12 min then
52 mW (810 nm) for 12 min;
once per day, 6 days per week for 12 weeks;

Placebo group switched to PBM after 12 weeks.		 Responders to PBM treatment showed improvements in all sub-scores of MDS-UPDRS-III scores (facial expression, upper limb, lower limb, gait and tremors) after 12 weeks, while placebo responders showed improvements in only lower limb sub-score.

PBM = photobiomodulation; H&Y = Hoehn and Yahr; LED = light emitting diode; RCT = randomized placebo-controlled trial.