Autism is somehow related. In people with ME/CFS you see family histories of autism, Asperger's, ADHD, fibromyalgia, prostate cancer, leukemia, lymphoma, bipolar disorder and other neuropsychiatric problems, MS, ATLS, Alzheimer's, Parkinson's, IBS, Crohn's, UC, etc.
I think it's widely accepted that autism is a genetic thing, but some researchers suspect autism is not, and that it's more like an infection that could be reversed or cured. I believe that all of those illnesses have genetic predispositions but are activated by things we get infected with, which are all around us, so it's hard to avoid getting infected by them. A healthy person could avoid getting infected, but if you run into an infectious agent while you have the flu, for example, your immune system is overwhelmed, or if your body has gotten overloaded with mercury or toxins.
I have a lot to say about women versus men:
Don't women have some very clear immune system differences than men, since their bodies are made to carry a baby which is "foreign" to the body? I think that's the main reason why women get ME/CFS more.
In some other illnesses where women are more affected, they say it's because the higher testosterone levels in men are protective. I think that's a factor for ME/CFS too. There are also other clear hormonal differences between men and women (progesterone and others).
I also suspect that women are more likely to get infected if their body was stressed due to a pregnancy in the past few years. During the pregnancy their body will manufacture extra good hormones to keep them going, but I think most women will have postpartum depression because their body is fatigued from what it's gone through. Then add on top of that, they are waking frequently to care for their new baby.
And I suspect that women have less frequent orgasms than men in general and that is a small factor too. Orgasm triggers lots of hormonal and neurotransmitter changes and I believe it helps the immune system and other body systems.
Women are more likely to have eating disorders or go on crazy diets. I think the typical woman watches her fat intake more than a typical man, and this means their body has less resources when an infection comes around. I know there are many exceptions but I think this is a real factor for many women.
I hate to say it, please don't take this the wrong way, but I think studies prove that women have more trouble with emotional stress too. I don't mean that women are weaker necessarily but they handle things differently because they were taught that or maybe for biological/hormonal reasons. I suspect that women are under a lot of pressures than men don't have. (Not to say that men have it easier, but their expectations are more physical or mental than emotional.) I won't get into the details but I think anyone who is going through emotional stress has a weaker immune system for that time, and some time after.
I also suspect that men are more likely to use alcohol and drugs more often. I am not talking about alcoholism. I mean in moderation. I personally believe alcohol and most drugs are protective against some kinds of infections.
In addition, what has been proven in the medical system. Women seek help, but it takes them years longer to get it, than the men who seek help. I think some of those men get helped quickly enough that they can overcome the infections.