Yes, low blood pressure can cause depression. Although researchers are not conclusively certain that having low blood pressure necessarily causes individuals to be susceptible to anxiety and depression, they haven't denied the possibility of the two relating. It is however important that you visit a qualified physician for expert analysis.
sometimes....also depend on the environment also...but its highly probable, my best friend has LBP and she's deppressed a lot, more than I get....but there are foods that can help treat that, though curing it is a different story! Leafy greens: Broccli, spinach, cabbage, banana, mangoes etc, help with that