When we talk about seasonal depression, the short, frosty days of winter probably come to mind. After all, the bulk of people who experience seasonal mood changes feel the most stress and anxiety during the thick of winter .

But seasonal affective disorder can happen at any time, in any season. And right now, as we transition away from summer and settle into our new fall routines, many people will notice that theyre feeling a bit more anxious or melancholy than they did a month ago.

This time of year, when the days become shorter, you can already start to develop some of the symptoms of the seasonal pattern of depression even if it doesnt rise to the level of a medical diagnosis, Dr. Eric Golden , a psychiatrist at University of Pittsburgh Medical Centers Western Psychiatric Hospital, told HuffPost.

Heres why fall can cause so much anxiety or sadness

There are multiple reasons as to why the change in seasons affects our mood. For one, our schedules tend to ramp up in the fall and with that comes new stressors and responsibilities that can impact our well-being .

The days are also getting shorter and were less exposed to sunlight. According to Dr. Paul Desan , an associate professor of psychiatry at Yale School of Medicine, the brain is pretty sensitive to the light-dark cycle.

Scientists are still learning about all the ways in which daylight impacts the neurotransmitters in our brain that influence how we feel, but growing evidence suggests that the change in seasons can trigger chemical changes in the brain. We know, for example, that lower levels of daylight are associated with lower levels of serotonin the neurotransmitter thats associated with depression and mood regulation, Golden said.

Lastly, some peoples brains may start preparing for the fact that winter is approaching. If they experience seasonal depression or anxiety in past years, they may get anxious that the hardest time of year for them is right around the corner, Desan explained.

Seasonal mood changes are a spectrum. According to Desan, data has shown that most people feel better in the summer than the winter, but the symptoms can really vary in terms of severity. Some may only experience milder symptoms, like less energy, while others will develop major depressive disorder.

Much of this is influenced by a mix of risk factors , such as your underlying health, family history, where you live, along with your age and gender. The main takeaway, however, is that most people feel worse in the winter and better in the summer, Desan said.