As I've said a few posts before: If my depression had to do with a Vitamin D deficiency, it should be gone during the summer, when I spend a lot of time outside. Also, I am taking Vitamin D in the winter together with my B12.
But it's the winter, and you're still depressed. Not to mention you're willfully ignoring the wide array of studies and data that overwhelmingly shows links between sun exposure and mental health benefits. For someone who's desperate for solutions, and yet you're not exploring all the avenues available to you, is in a way a sign of mental illness.
Synthetic vitamin D cannot be absorbed by the body at the large requirements one requires when there is a nutrient/vitamin/mineral/hormone deficiency going on (which is all depression is really) and UV radiation exposure in amounts that don't cause you to sunburn will produce 4-5 times the amount of vitamin D that is considered unsafe to take orally.
In comparison, full-body sunbathing for a period of time that will just make you turn pink will produce 10,000-20,000 IU of vitamin D, equivalent to 100 to 200 glasses of fortified milk. Given such copious production, relatively casual sun exposure (arms, etc) should meet vitamin-D needs.
The importance of solar-produced vitamin D was underscored in a study that evaluated vitamin-D status in a submarine crew after two months of acute sun deprivation. Although the crew consumed a vitamin-D fortified diet, their levels of this nutrient plummeted.http://www.healingtherapies.info/sunlight&vitamind.htm
Vitamin D can be toxic if too much is consumed from supplements or mistakenly over-fortified foods. However, prolonged sun exposure does not generate toxic vitamin-D levels due to the body’s feedback regulatory mechanisms.
Furthermore, what I'm reading from that webpage is again backed up and sourced in The China Study, by T. Colin Campbell