Because people with diabetes can feel depressed when their blood sugar levels drop, the first step in managing seasonal affective disorder (SAD) is to take control of your blood glucose. That means eating regular meals, choosing whole foods that have lots of fiber, and avoiding processed foods and sugar when possible. Here are some other tips for maintaining or recovering a positive mood in the winter:

• Exercise. Exercising regularly can improve blood sugar control, increase energy levels, lead to better sleep, and trigger the release of hormones and other chemicals associated with positive mood and contentment.
• Light therapy. Light therapy has been shown in some research to help people with SAD, and has even been found to improve insulin sensitivity in people with diabetes, decrease carbohydrate cravings, and improve sleep.
• Certain supplements. Supplements such as B-complex vitamins, vitamin D, and omega-3 fatty acids from fish may have a role to play in helping you with wintertime depression, but speak with your doctor before beginning any supplement regimen.

Source: Psychiatry Research