Preschooler depressed?

My four-year-old daughter seems to be whiney and crying more than she is happy.  I am worried that she may be depressed.  I have suffered from depression since I was a child and have been on medication for more than 15 years (with successful results).  My brother's depression caused him to take his own life, and my sister suffers some depression related to ADHD.  

Aside from the family history, my daughter is experiencing separation anxiety any time we part.  when she is whining or crying, I ask her what is bothering her and she often says that she doesn't know.  She has been having problems making simple decisions (such as what to play wih first, a puzzle or her crayons) and will say that she just can't decide and end up in tears.  It doesn't halp when I try to help her make a decision or try to guess what is bothering her.

Can children her age be depressed or is this just a long phase she is going through?

[Mili2004]

I heard they can. Sorry to hear about your family problems. The speaker who mentioned that, said the children are too overwhelmed with so many activities they cannot rest, they get anxious and depressed as little as 4 years old.
I remember being a depressed 10 years old child also. My parents had marital problems back then. Consequently, I gained weight because I started eating too much carbs and the depression got worse. I realized eventually that a good diet, exercise, out doors activities and positive thinking made me overcome my early depressions that were very deep in some point. I did not take medication; maybe my case was not that severe.

[jdtm]

Our child was diagnosed with depression at six years of age.  I expect a child could be suffering from depression at four years of age.  Please see your family doctor.