Here's another study about low level laser therapy, this time studying the effects on chronic rhinosinusitis, with positive results lasting for an average of 5 months:
Chronic rhinosinusitis (CRS) is a common inflammatory disease of the nose and paranasal sinuses that has a significant impact on patients' quality of life. The aim of this study was to evaluate the effect of LLLT in patients with CRS. Fifteen adult patients with CRS participated in this pilot pretest-posttest clinical study...
Patients were asked to score their symptoms in accordance with a four-point scale (0-3), and a total symptom score for each patient was calculated. Percentage improvement of TSS was considered as the primary outcome measure. TSS was calculated at baseline, at 2 weeks, and at 4 weeks. The TSS was improved significantly at 2 weeks (39%) and at 4 weeks (46.34%). The therapeutic effect was sustained for a mean of 5 months. [Emphasis added.] This pilot study indicates that LLLT applied for 4 weeks improves symptoms in patients with CRS.
Physiother Theory Pract. 2013 Mar 22 (Epub ahead of print)