The summer got off to a slow start in Santa Monica, Calif., -- and Saskia Smith could not have been more pleased.
"We had two months of relative cool and cloud coverage," she recalled. "That really was like a soothing balm."
But then the weather got warmer. And unlike the throngs of sun worshippers who head to the outdoors at the first sign of warm weather, the 32-year-old Smith said for her the summer months bring about depression and anxiety.
"I look outside now, and I acknowledge a perfect, beautiful blue sky," she said. "But then I look at the sun and the heat coming off the pavement and I say, 'Ugh, I don't want to go outside.'"
It may seem like an unusual reaction, and it is; psychology experts say only a handful of people experience this particular variation of what is known as seasonal depression. And some even doubt that a depressive condition specifically linked to the summer months actually exists.
"As a clinical psychologist in the practice and research sphere, my understanding is that 'reverse' seasonal affective disorder is not a true disorder or diagnosis and is mentioned only a few times in the existing clinical literature," said Katherine Muller, assistant professor of psychiatry at Montefiore Medical Center in New York. "Depending on the presenting symptoms, clinicians would likely label this as a mood disorder and offer treatments that we know are effective for depression, such as antidepressant medications and/or cognitive behavioral psychotherapy."
Smith is not alone, however. John, 73, of Oregon (who requested that his full name be withheld) said he has experienced periods of depression, each lasting for several months, that have coincided with seven of the last eight summers. At the time John spoke with ABCNews.com, he said he was in the midst of just such an episode.
"They typically start around May, and they tend to go into some degree of remission between September and November," John said.
But during these months, he said, the symptoms he experiences are debilitating. "Things that I enjoy doing, I lose all enthusiasm for," he said. "I experience what is known as anhedonia -- joylessness, an inability to experience pleasure."
And even though John has experience helping others discover the root of their depression -- he is a psychologist himself -- he said that when it comes to the origins of his own depression, he is at a loss.
"I'm really stumped," he said. "I have no good sense for what brings these episodes on."
People who say they suffer from summer-onset depression face what many would consider a rough deal. Not only do their depressive symptoms occur during a season normally associated with recreation and fun, but they also strike at a time when psychiatrists and therapists are notorious for taking their August vacations.
But despite the scarcity of scientific literature on summer depression, research on seasonal affective disorder -- or by the evocative acronym SAD -- has led to a greater acceptance that winter blues, at least, are a legitimate diagnosis.
SAD is normally associated with depression, lethargy, fatigue and other symptoms that coincide with the colder, darker months of the year. According to the National Institute of Mental Health, up to 10 million people in the United States have some degree of winter-onset depression.
A number of studies dating back to the early 1980s suggest that these depressive symptoms are consequences of too little light, and today researchers believe that a dearth of light can lead to low levels of serotonin in the brain. This chemical plays an important role in mood regulation and proper sleep-wake cycles.
Dr. Alfred Lewy, director of the Sleep and Mood Disorders Laboratory at Oregon Health and Science University, published a paper in the journal Proceedings of the National Academy of Sciences three years ago in which he and his colleagues found convincing evidence that winter SAD was a result of a concept known as "circadian misalignment" -- a jet lag-like disruption of sleep/wake patterns brought about by a change in the seasons.
The root cause of summer depression is much less clear. Lewy said that the first real studies conducted to determine the existence of a summer version of SAD were conducted in 1991 by Dr. Thomas Wehr of the National Institute of Mental Health and colleagues. He said that these initial studies showed that in general, sufferers tended to experience a different range of symptoms than their winter SAD counterparts.
"In people with summer depression, you see a decreased appetite and insomnia; with winter depression, you get an increased appetite and increased sleep," Lewy said.
It is a feeling with which Smith is familiar.
"I started getting anxiety... It's very difficult because there is nowhere to escape," Smith said. "I liken it to feeling like a little insect under a magnifying glass. All you can do is hide away in a dark place."
But because cases of summer depression are relatively rare -- less than 1 percent of the population, by some estimates -- researchers in the field have a difficult time finding enough people with the condition to conduct large studies. Lewy said he has encountered only a few patients who seem to have depression linked to the approach of summer.
Still, he said, this does not mean that summer-onset depression doesn't exist.
"It's a fairly rare disorder, but I think Dr. Wehr is on to something," Lewy said. But as for the underlying causes, he added, "We don't know the answer to that."
Smith said that when she has too much exposure to the bright sun of summer, her symptoms can range from irritability to anxiety and panic attacks.
"It becomes very disabling at a certain point," she said. "At my lowest point I felt very suicidal."
Fortunately, Lewy said, existing treatments for depression are generally effective for those who experience similar symptoms. "As far as I know, the antidepressant that is used to treat non-seasonal depression has also been used in treating summer depression and winter depression," he said.
While Smith said that she has never taken antidepressants or any other medication, relying instead on supplements and other non-medical remedies, she has also found other ways to deal with the condition. She said that she even makes it a point to leave town during the worst of the summer months to head for a cooler, less sunny locale for a couple of weeks. Smith also manages a community web site for others who experience summer depression.
Lewy said that as researchers and clinicians discover more about the disorder, new treatment options may become available. He said that he is currently working to establish whether levels of another brain chemical known as melatonin might have anything to do with the phenomenon -- and whether treatment with it could be the key to relieving the symptoms in some.
"Summer depression may eventually be treated with dark or orange goggles that block out blue light," he said. "Perhaps we will use a low dose of melatonin to adjust the 24-hour cycle, or some other intervention. But as to whether this would help, that research still needs to be done."