Disruptions in mood often accompany the onset of a new season, either remission or onset of depressive episodes. This phenomenon was referred to as "Seasonal Affective Disorder" (SAD) in DSM-IV. It's now listed under "Depressive Disorder with Seasonal Pattern." Episodes typically emerge in fall or winter, and remit in the spring. There are also cases that do not fit this pattern, as many people report episodes of low mood with the onset of spring. The challenging and overlong winter many of us have just survived, along with a seemingly abrupt change to milder weather, may account for current depressive symptoms.
I've suffered from major depression throughout my adult life, and experience a dramatic drop in mood during the first few days of January, a drop that digs in for the rest of the winter. I also feel uplifted in the fall, and get mixed results in the spring.
Seasonal depression often presents as a decrease in energy, overeating, craving carbohydrates, weight gain, and sleeping longer than normally...or at least staying in bed longer than usual. These symptoms are not exclusive to seasonal depression, and other symptoms are known to manifest as well. We also know that, due in part to the increased production of melatonin and the availability of Vitamin D, people who live in moderate climates combined with reliable sunshine suffer fewer symptoms of depression over the life span than their peers in colder or four-season climates.
Although suffering from depressive symptoms when winter changes to spring is less common, the symptoms also tend to remit more quickly as we adjust to the warmth and sunshine, and we can look forward to more stable mood states up until the fall (for those who experience seasonal effects).
The good news is that, if it's not a case of major depression, it doesn't last forever.