**9. Conclusion**

tPBM is the utilization of LLLT which is thought to modulate mitochondrial activity, ATP synthesis, and biosignaling processes [13, 14]. While comprehensive understanding of the mechanisms that underlie this modality remain elusive, LLLT interventions have shown efficacy in pediatric epilepsy as adjunctive therapies to AEDs and across neurodegenerative disorders [12, 59, 62].

Considerations of quantum mechanics suggest that the clinical utility of tPBM is related to the ability of cells to derive free energy from water [23, 41–43]. As the advent of femtosecond spectroscopy has allowed for the study of the dynamic processes that underlie chemical reactions and molecular rearrangement after exposure to laser technology, the ability of LLLT therapies to induce photochemical alterations within mitochondrial pathways has become possible [12, 23, 42–47].

CCO is an endogenous photoreceptor which is implicated in electron transfer and metabolic processes [59]. This molecule is implicated as a targeted mechanism of tPBM as it is a photoreceptor that can absorb photons to increase ATP synthesis within the mitochondrial respiratory chain [19, 59]. As hypoxia is thought to underlie the etiopathogenesis of AD, the ability of tPBM to alter biological signaling via exposure to QLEDs is a significant advancement in clinical medicine [12, 16, 42–47].

Applications of quantum mechanics to the study of light therapy interventions suggest that the cosine emission law and the inverse square law of illuminance are relevant to the pharmacodynamic processes that underlie clinical responsivity to tPBM [28, 36–40]. The inverse square law of illuminance states that the light received by any surface is dependent upon the distance of the targeted surface in relation to the source of light [39, 40]. Considerations of the cosine emissions law indicate that the intensity of light covaries according to the distribution area of the light and its angle of incidence [28, 36–38].

As the pharmacodynamic parameters tPBM may vary according to water concentration levels across human tissues, considerations of wavelength, time course of exposure, and scattering effects must be examined prior to clinical applications of this intervention [48]. These factors suggest that individualized dose response curves *Pharmacodynamic Implications of Transcranial Photobiomodulation and Quantum Physics… DOI: http://dx.doi.org/10.5772/intechopen.106553*

may be required despite robust utilization of 670 to 1040 nm of near infrared and infrared light tPBM interventions [59–61].

Continued research of applications of quantum physics and photochemical responses in the development of precision medicine therapeutics is required. As the clinical efficacy of LLLTs is being examined as electromagnetic interventions that may curtail neurodegenerative processes, this suggests that exposure to NIR and IR therapies may modulate functional mitochondrial pathways [1, 7, 12, 16, 27, 28]. Current examinations of therapeutic responses to LLLTs suggest that the clinical utility and pharmacodynamics of these interventions may require multifactorial analyses which include, but are not limited to age, depth of the targeted tissue, and body mass [48]. Future directions of clinical research for LLLT interventions must seek to establish proper irradiation parameters and time course exposure to near infrared and infrared light therapeutics [28, 30, 31]. These implications suggest that clinical responsivity may not only vary according to the frequency of exposure to tPBM interventions but also according to the severity level and symptomatic profile of the disorder by which this intervention is applied.
