My thoughts are it's MTHFR gene mutations. Read through these links.
–"A defective MTHFR gene creates a vulnerability to disease processes as detoxification is impaired, leaving the body more susceptible to oxidative stress, and less tolerant of toxins such as heavy metals."
https://thevaccinereaction.org/2017/05/mthfr-mutations/
–"Who Should Know About MTHFR?
This article may be of greatest interest to those who have been diagnosed with one of the mental health issues linked to having an MTHFR mutation, such as depression, bipolar disorder, schizophrenia, attention-deficit hyperactivity disorder (ADHD), or autism."
https://www.psychologytoday.com/us/blog/the-integrationist/201409/genetic-mutation-can-affect-mental-physical-health
–"An increased vulnerability to oxidative stress and a decreased capacity for methylation may contribute to the development and clinical manifestation of autism."
https://academic.oup.com/ajcn/article/80/6/1611/4690493