When the sun sets early in the day and the cold weather sets in, humans can find themselves suffering from the "winter blahs" to the more severe Seasonal Affective Disorder (SAD).
If you see your pets lounging around on gray winter days, they're not just following your lead but may be suffering from the winter blues too.
That was the case with Max Marvin, the human founder of Pawsitive Lighting, an Oregon-based company that offers a light box, a common treatment for humans with SAD, designed specifically for pets.
When Marvin found himself battling a severe case of insomnia, he began using a light box for 30 minutes every morning at the advice of a sleep specialist. The light box therapy worked for Marvin, and, to his surprise, also helped his golden retriever, Luke.
"Luke and I were both basking in the sun every single morning and I found that he was just completely drawn to the light," Marvin told ABC News' Dan Harris. "Luke would just be on his back enjoying the light, happy as can be."
After research and consultations with veterinarians confirmed Marvin's hunch that pets could suffer from SAD just like their owners, he partnered with a British light-therapy device manufacturer and developed the Sol Box, a 10,000 lux light box just for pets.
"Pawsitive Lighting was founded because no one was providing a holistic approach to the treatment of depression in pets," Marvin writes on his company's website. "Increasingly vets prescribe Prozac and other antidepressants in an attempt to boost their serotonin levels. That seemed rather cruel."
The $199 Sol Box can be used by pets all day long and promises to help your dog or cat enjoy "increased energy, decreased anxiety, enhanced sleep and elevated mood," according to the website.
Veterinarians like Dr. Marty Becker say Marvin is on to something in believing that pets, like humans, can become depressed.
"Unlike humans, pets don't fake it. They don't say I don't want to show up to work today so I'll call in sick, right?" Becker told ABC News. "But if you eliminate all the other things that are true problems, then you'd have to look from the fact that this pet may be depressed."