Seasonal depression or "Seasonal Affective Disorder" (SAD) is a type of depression that recurs on a seasonal basis. Mostly this occurs in the winter months and is more prevalent in regions with significantly less light or worse weather during winter. Scientists believe reduced exposure to sunlight, an increased production of Melatonin, a lower level of Serotonin and a change in the body's internal clock (circadian rhythm) are some causes of SAD.
Lack of sunlight is manageable now thanks to sunlight-mimicking devices called "Light Boxes". There are many to choose from and these devices are getting better and better at mimicking the affects of the Sun on our bodies. All you need is to sit in front of one for 30 minutes a day. Most choose to do so in the mornings which also helps set a better sleep and waking up cycle (circadian rhythm).
Gift Tip: This makes a great gift for individuals living in northern states or countries where days are short and nights long during winter months.