The short days and low light levels of winter may be proving particularly difficult for some.
Seasonal affective disorder, or SAD, is estimated to impact the lives of at least 10 million Americans each year, and is generally observed to peak during the winter months.
Possible symptoms include lethargy, lack of appetite or (conversely) overeating, disruption to normal sleep patterns, depression and, in more extreme cases, feelings of suicide.
Simple measures, including ensuring daily exercise, remaining well hydrated and moving close to a window when the sun is out, can go some way to tackling milder forms of the condition, experts say.
Nutritional health supplements and herbal supplements may also prove useful health resources for battling low mood during the winter months and beyond.
According to the Mayo Clinic, seasonal affective disorder normally commences in early adulthood although it is not common in people under 20.
The incidence of SAD rises in more northern regions, and is believed to decline with age. Its precise mechanisms are not yet properly understood by experts, although links have been made with changes in the bodys melatonin and serotonin levels during periods of low light. 