Do drawings depict hidden things about the artist in them?

All artworks are the physicality of an artist's practice. So yes, I'd say that a lot about the artist is hidden in an artwork. Anger, unsecurity, drug usage, etc translate into specific structural qualities in a drawing. My drawings are uniquely mine, for reasons I can't quite pinpoint but exist somewhere, hidden in my lines.

A teacher once told me that inexperienced artists often draw themselves when drawing the human figure, even when working from a live model. Good drawers are less likely to make this mistake, but everyone will still draw the same model differently, so it makes sense that something of the artist is in the drawing.

Here's a quote from Oscar Wilde's "The Picture of Dorian Gray" which I thought fitted your question pretty well. The painter Basil says this after he paints a portrait of Dorian, and refuses to show it to anyone.

"I have put too much of myself into it.... Every portrait that is painted with feeling is a portrait of the artist, not of the sitter. The sitter is merely the accident, the occasion. It is not he who is revealed by the painter; it is rather the painter who, on the coloured canvas, reveals himself. The reason I will not exhibit this picture is that I am afraid that I have shown in it the secret of my own soul."

yes very much so. well at least for serious artist. every line in a drawing shows how an artist feels and the subject of the drawing shows what the artist thinks about.

Frequently, for example, a portrait artist will try to include the character of the sitter in their piece, in making that choice and the choices they make they might be showing something of their own character.

However just by viewing one or few images it would be difficult/fruitless/impossible to try to draw conclusions about the state of mind of the artist.

I do know! I hate when parents say its 'satanic!' its not! That's just racist, critisizing jap drawings... In any case, i might reccommend getting a plastic box and hiding it, like below a bush or whatever, or maybe inside of a pocket in a enormous wintry weather coat within the closet? Beneath the couch? Beneath the television. In an un-used kitchen cupboard? At the back of a bulliton board/ or a reflect? Underneath the computing device pc? Inside of a image body in the back of a picture? Under the dvd participant? Hold them on your locker at college?