Alright, so this sounds crazy but based on these research findings it is safe to assume that meth would allow wounds and diseases to heal faster by interleukin 6 . On the otherhand, using meth during illness would cause higher neurotoxicity due to extreme hyperthermia and fever.
Correct me if I'm wrong:
Firstly, dopamine increases interleukin 6 (IL-6) release and inhibits tumor necrosis factor release. Interleukin-6 is the source of fevers and hyperthermia. Most importantly, IL-6 heals skin wounds. It's main goal is to regulate the immune system by raising and lowering temperature depending on if a person is sick or not. Raising body temperature will prevent a person from being sick and will make wounds heal faster, but will induce neurotoxicity, lowering it will prevent neurotoxicity but make someone vulnerable to infection. According to Wikipedia, IL-6 stimulates the inflammatory and auto-immune processes in many diseases such as diabetes, atherosclerosis, depression, Alzheimer's Disease (interestingly though, Alzheimer disease is reliant on dopamine depletion, and people with Alzheimer had significantly higher levels of IL-6, which is surprising. One possibility is due to the fact that dopamine increases interleukin 6 release, and without dopamine, IL-6 cant be released, meaning more IL-6 will be metabolized but not used).
IL-6 is also the main, and perhaps only, cause of meth-induced neurotoxicity. It is responsible for neurotoxicity by means including, but not limited to, cell death, ROS generation, and neuronal damage. Lowering enviromental temprature significantly prevents neurotoxicity. To verify this claim, I Googled "methamphetamine neurotoxicity interleukin-6", and came to this article, furthering the evidence that meth vastly potentiates IL-6 and IL-6 induced hyperthermia is the result of meth-induced neurotoxocity, as mice with a mutation for IL-6 blocked meth-induced neurotoxicity, which also means that these mice won't be able to reheal faster.
To bring an update to this post, I have found this paper that shows that happiness potentiates the immune system. But this is a very minor influence as meth produces >1000 "units" of dopamine, relative to 300 units which cocaine produces. Meth would be much more efficient.
To bring further updates, it seems that my assumptions were correct. By googling "site:nih.gov methamphetamine neuroprotective", I was led to the following: https://www.ncbi.nlm.nih.gov/pubmed/24333768 and https://www.ncbi.nlm.nih.gov/pubmed/25724762
Surprisingly it is neuroprotective following stroke.
So, putting all this into account, is it possible that meth actually heals wounds and diseases (while at the same time inducing neurotoxicity)?
This assumption came to me because I have an aggressive cat and whenever I'm high on meth I noticed how wounds from a cat scratch would heal within a day or two instead of a week.