Just recently it has been brought to light that negative ions may help with the symptoms of SAD. This article covers what these are and how they can help.
To quote :
Not everyone with seasonal affective disorder (SAD) can afford to slumber amidst the babbling mist of a nearby brook with the gentle caress of the day’s first sun softly nudging them awake. It’s ideal, but studies indicate that simulating those conditions with negative ion generators, naturalistic dawn simulating lights, and someone blowing raspberries at your face can be just as effective at combating SAD as bright light therapy (okay, maybe not that last one).
Chronic non-seasonal depression has also been shown to be improved with negative ion therapy. High density ion therapy was far more effective than low density ion therapy.
Negative ions (along with bright light and auditory stimuli) reduced subjective measurements of depression, improved mood, and reduced anger in both depressed and non-depressed college students.”