There seems to be a great variability of the time it takes for patients to notice an effect from LDN. There are so many factors that effect this including the patient, the dose and what condition is being treated.
I have seen anywhere from literally one hour after taking the medicine to several months. Inflammatory conditions seem to respond faster in my experience, neurodegenerative conditions seem to take the longest. Something like MS or Parkinson’s Disease it could be up to a year.