Changes in sunlight can upset our circadian rhythms — and disrupt our moods. A clinical psychologist explains how seasonal affective disorder can still happen in the summer.

Seasonal affective disorder (SAD) is commonly linked to the colder months, but a lesser-known variant can also occur in the summer. While winter SAD often leads to social withdrawal, excessive sleep, and increased appetite, the summer version can cause restlessness, insomnia, and reduced appetite. 

Experts explain that these mood changes are tied to disruptions in circadian rhythms, which are sensitive to changes in sunlight and daily routines. Strategies to manage summer SAD include adapting sleeping environments, staying active, and maintaining social connections. Consulting a healthcare professional is also recommended for those experiencing significant symptoms.

Summertime sadness is a real thing. Here’s what you need to know

Winter is over. The sun is shining, birds are singing, flowers are blooming, but maybe your mood isn't reflecting the nicer weather. If that's the case, you could be dealing with seasonal depression in the summer. As Canadians, many of us know about the winter blues. An unfortunate minority of Canadians know about winter seasonal affective disorder, which is a depressive episode that coincides with changes in the seasons, usually as we're making that transition into the fall-winter period. Now a lesser known, but still important and disabling variant of this is summer seasonal affective disorder. Winter seasonal affective disorder can cause people to feel sad or hopeless. While it's not a standalone diagnosis, it can be diagnosed as major depressive disorder with seasonal patterns. The summer version of this, Sherry says, can have both similar and opposite symptoms. You'll get the theme with the winter side of things. It starts to sound like the bears go into the caves, that there's a hibernation-like state occurring, and that involves social withdrawal on the winter side of the symptoms. Whereas in the summer, you might see more of a restlessness and an agitation. You're going to see a somewhat different symptom profile if we try and contrast the winter and summer patterns. For instance, you're going to see sleep problems in both cases. But in the winter, you tend to have people sleeping way too much. Whereas in the summer, you may find that people are actually suffering more from insomnia. They can't get to sleep. So there's a contrast there. There also seems to be a contrast where in the winter, people are more prone to overeating and to unnecessary weight gain. Whereas in contrast, in the summer, you're going to see people on average losing some weight and having a poor appetite. So if winter seasonal affective disorder is triggered by the loss of sunlight, why do people experience depressive symptoms in the summer? Well, Sherry says it has to do with our circadian rhythm, or our sleep clock. It's a biological process that tells us when to sleep and when to wake up. If that gets disrupted, Sherry says, our moods can become dysregulated. In the summer, for example, the sun rises much earlier and sets much later, throwing our winter sleeping patterns into disorder. Our circadian rhythm is sensitive. One example would be the time changes we undergo here. That's just one hour. But that spring ahead, fall back is quite consequential. Even though an hour time change in our circadian rhythm seems small, you'll find more accidents, more new onset cases of depression, more suicide deaths, more consumption of substances. So this circadian rhythm is fairly finely calibrated, and even a small deviation from it can be important. While fighting seasonal depression in the winter can look more like taking your vitamin D or using light therapy, Sherry says the summer is all about adapting to your environment. He suggests re-engineering your sleeping environment, using sleeping masks or thicker curtains. Embrace the stuffy weather, doubling up on sunscreen and water to go for walks. You can also talk to a health care professional or psychiatrist, but Sherry says not isolating yourself is one of the best strategies in fighting seasonal affective disorder. So whether it's summer, winter, or otherwise, it's important to remain engaged and to participate in activities so you're not living a sheltered and unsatisfying life.

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