Not all miracles are adequately explained by scientific factors. However, that some people could be healed by the so-called placebo effect is a possible explanation worth considering.
According to the Harvard Medical School, it is possible for the mind to help treat a physical ailment. However, the placebo effect encompasses more than merely the power of positive thinking, because the effect is that the mind can trick the body into believing that it must help stimulate an autoimmune healing process.
The Harvard Medical School also points to scientific data that supports the success of the placebo effect as a legitimate treatment for certain medical issues. For instance, medical professionals do not believe that the placebo effect can effectively treat cholesterol or tumors, but they have found that it can help with pain management and with treating conditions such as stress-related insomnia, fatigue, and nausea that often accompany traditional treatments of illnesses.
With some faith-based healing that Jesus and the disciples practiced, it seems likely that the powerful effect the mind can exert on the body in stimulating physical improvements could have been at play. For this reason, the power or degree of the faith involved can be an important factor. For someone who was skeptical about the healer’s ability to help with treatment, there was probably not as great an improvement as there might have been with another person who had greater faith in the process and power of the faith-based healer, depending on the underlying medical condition.