Personal observation: As a transsexual person who cannot take estrogen orally, I rely on Premarin which I take daily. If I miss several days I will feel depressed. The estrogen in Premarin is necessary so my body will make a sufficient supply of serotonin without which I feel depressed.
The autism/antidepressant link may have to do with serotonin metabolism, which is also impacted by vitamin D. The link between vitamin D deficiency in pregnant women and the proportionate jump in autism has been highlighted by Vitamin D Council founder Dr. John Cannell and others.
Vitamin D receptors appear in a wide variety of brain tissue early in the fetal development, and activated vitamin D receptors increase nerve growth in your brain.
In addition, according to a study by the Children's Hospital Oakland Research Institute, vitamin D may affect autistic behavior by activating a gene responsible for the production of tryptophan hydroxylase 2 (TPH2), an enzyme that converts tryptophan to serotonin in your brain.10
The research also shows that two other brain hormones associated with social behavior, oxytocin and vasopressin, are activated by vitamin D. As reported by Newswise:11
"This suggests that adequate levels of vitamin D may be required to produce serotonin in the brain where it shapes the structure and wiring of the brain, acts as a neurotransmitter, and affects social behavior.
They also found evidence that the gene that makes the enzyme tryptophan hydroxylase 1 (TPH1) is inhibited by vitamin D hormone, which subsequently halts the production of serotonin in the gut and other tissues, where when found in excess it promotes inflammation.
This mechanism explains many of the known, but previously not understood, facts about autism including:
1) The 'serotonin anomaly' low levels of serotonin in the brain and high levels in the blood of autistic children
2) The preponderance of male over female autistic children: estrogen, a similar steroid hormone, can also boost the brain levels of serotonin in girls
3) The presence of autoimmune antibodies to the fetal brain in the mothers of autistic children: vitamin D regulates the production of regulatory T-cells via repression of TPH1."
The researchers propose treating ASD with a combination of vitamin D, tryptophan and omega-3 fats in order to naturally elevate the concentration of brain serotonin without side effects. This isn't the first time vitamin D has been implicated as a contributing factor to rising autism rates.
According to previous research, there is indeed a link between rampant vitamin D deficiency in pregnant women and the proportionate jump in autism.12