Interesting. After reading your comment on Friday, now it is my third day on 5000 IUO, I did not really dare to try 10, so far not much of an effect. Probably masked by having visited a rural friend on Sunday who always has homemade brandy ready, well, I guess I won because he fell asleep and I didn't, still, there is hangover :)

You male? Heard about Vit D and testosterone being connected and T shots being used to treat male depression with some success. To test this: combine it with zinc, zinc deficiency is also fairly common and can be a T bottleneck.

On causality - I tend to look at these things differently. For example when they treat depression with exercise, it is more useful to look at it the opposite way: any natural animal would get a lot of exercise. Lacking it must cause some sort of a symptom, depression being in this case. And perhaps the same thing can be said about sunlight, the most natural thing for an animal is to run around in it, spending our lives in artificial caves must have some sort of an effect.