It may be due to the colder seasons because they can promote mental health issues such as seasonal depression, major depressive disorder, and anxiety. It’s also said that the reduced level of sunlight in colder seasons winter on-set seasonal affective disorder (AKA SAD).
What is it?

SAD- Seasonal Affective Disorder is a mood disorder that happens every year around the same time. It’s more common in the winter, though some people can experience it going into summer. It can affect people in any season and weather.
What happens?
Appetite might change, in particular, people with SAD tend to crave foods high in carbohydrates. The lower levels of serotonin, because these foods high in carbs tend to get our mood boosted and our energy levels, in short. If you have another mental health condition, you might find that your symptoms get worse when you’re affected by SAD. Different symptoms of SAD are agitation, feeling super sluggish/tired, changes in appetite or weight, insomnia, low energy, feeling hopeless or worthless, having difficulty focusing, social withdrawal, and others like depression.
Causes?
The exact causes of this mental condition are unclear, but it’s often linked back to reduced sunlight in winter. It can affect your body clock, lower light levels in winter can affect your melatonin levels and the “clock” your body uses to wake up or sleep. People with SAD may produce more melatonin, making them more tired, and their production of serotonin, a hormone affecting sleep, mood, and appetite. These lower sun levels can cause lower levels of serotonin, making them feel depressed.

You are more likely to develop SAD if you have something that will go hand in hand with SAD (depression or anxiety).

Cope?
Recommended treatment consists of the same as depression, through therapy and/or medication, this is because there isn’t enough evidence to show other types of treatment for SAD.
What can you do to help yourself? Light, especially natural light, exercise, or spending time in green places and plan in case, you can freeze meals if you know you won’t have the energy. You can also talk to someone like a therapist, keep a diary, and plan for difficult times. As I mentioned before, peer support, learning different ways to relax, looking after physical health, exercising, and eating well.

* Re-arrange stressful activities for another time, try different relaxing activities, plan ahead and stock up with things you need, make more spare time for yourself, or create a self-care box. SAD can be hard to deal with, but at least you can have a cheat sheet now.