All of the links provided are single paragraph abstracts. They are not studies and there is no link to any real information in any of them.
Sorry they all are pointless and may as well be the opinions of someone's mom. They are on a Web site that I don't use and I don't care to spend my time sourcing through their link lists to see if I can find the actual studies done.
It is very easy to write something that has no basis in reality and publish it in the Internet and provide some supporting link to nothing of importance. People assume because there are lots of links some might be real but they are all unsupported opinions with no basis.
Back to your original question is marijuana neurotoxin, I would say there is zero evidence of it.
There is some support that early teenage use of marijuana may inhibit proper development of your brains pleasure center. This is somewhat vague and will remain that way as the only proof would be human testing and we probably won't permit child testing. As a society we have a pattern of telling children the most outrageous lies to prevent them from exploring areas of life we deem unfit for minors. Marijuana has been one of the big lies we've been conditioning our children with. It may cause some mental dissonance to just accept it isn't harmful in 99.99% of situations and we are not sure the last .001% is harmful either but we don't feel good about the method we need to use to prove that.
The difficult part is realizing every person throughout your life that has told you "drugs are bad M'Kay" has bought into a lie and passed it on to you leaving doubt about everything they ever told you. If my trusted parents and all those obviously smart people in leadership rolls throughout my life were all willing to buy into a lie so easily, when marijuana turned out to be the best possible choice of medication I've ever used, what else did they lie to me about?
Once I got past this boogieman in my own head I never have had any anxiety from weed again. I don't think I have any anxiety about anything anymore.
Certainly I have changed mentally from the way I thought prior to extended marijuana use but these neurological changes are not toxic. I would even consider my mental position prior to marijuana was highly toxic, I was a mess. These changes did not happen overnight and there was a period where I stopped marijuana use for over 100 days to see if I would revert back to the mess I was before. I had a lot of anxious days, most days I was trying to persuade myself that I was justified in my use of marijuana and it wasn't hurting me. I studied my ass off and read everything I could find and realized all the hype about danger from weed was just hype. I dug through thousands of pages of Internet crap over a period of about one year and found the only deaths from weed were from police enforcing the lie about how bad it was for us. Only the lie was dangerous not the weed, despite their involvement I don't blame the police I think we give them horrible rules to enforce and they must hate their lives.
About 6 years into my 8 year use I experience an awakening that at first I called "spiritual awakening" now I just feel aware of my life and am confidant in my decisions. Marijuana may have triggered this event and there was some related anxiety while I realized how much of what I believed was simply wrong. Now I'm happy, employed at a challenging job with much better pay and function socially without giving up sobriety.
I don't want to promise others that weed will be the cure for them but I do want to stop the lies. Without real medically and scientifically backed data from a well run study there is nothing I fear from weed. I could certainly be wrong, I've been wrong before but if I find I've been wrong I'll post here. I don't have a pony in this race (I don't make money from either pro or con weed camps) my mental health was my only concern beyond the method of marijuana use which I choose edible so I didn't have to smoke anything. My litmus test has been my work, I was a nearly unemployable alcoholic making barely enough to rent a roof. Last month I was headhunted for a plant management position, I'm making a lot more. My enjoyment of life has improved in every way, even my sex life is off the charts. I've stopped waiting for the other shoe to drop and am just glad I didn't off myself when I was a useless drunk.