If you feel depressed, fatigued, and irritable shortly after this time change and you've noticed that this has occurred in previous years, you most likely have seasonal affective disorder (SAD). However, if your symptoms become severe enough that they significantly impact your typical daily routine or activities and you don't feel like you can’t get out of a "rut”, that would be a great time to see your primary care physician to get evaluated for other types of depression that may require a different course of therapy.