It's not uncommon to feel a dull lethargy engulfing you during the winter months. Some might call it "cabin fever," some label it the "winter blues" and some say they have "SAD" short for seasonal affective disorder. However, even if these terms seem to imply the same thing and occur around the same time of the year, they are not the same.

"Seasonal affective disorder is actually defined in the diagnostic manual as a type of major depression disorder, though it is unique in that it recurs in a seasonal cycle ," said Dr. Simon Kung, director of mood disorders program at the Mayo Clinic in Rochester, Minn.

"When a patient comes in and tells me she has the winter blues," Kung said, he tries to find out if it's something benign, or if she actually has symptoms that fit the profile of depression.

SAD affects about 1 to 10 percent of the adult population in the U.S., and sufferers are most likely to feel depressed during the winter months, when there are fewer daylight hours, Kung said. Like most other depression patients , they often experience depressed mood, diminished interest in daily activities, feelings of insignificance and diminished abilities to think or concentrate.

In addition, SAD sufferers are more likely than those with other types of depression to have symptoms such as sleepiness, carbohydrate cravings and interpersonal difficulties.

However, some patients with these symptoms might instead have an adjustment disorder, which can be brought on by temporary situational stresses unrelated to the time of the year, he said.

"For this to be SAD, the symptoms have to persist daily for more than two weeks, and they fit at least five out of the nine diagnostic criteria" in the Diagnostic and Statistical Manual of Mental Disorders (DSM), Kung said. "And most importantly, it has to occur seasonally."

Most patients go into remission and recovery after the depression phase. However, a small minority swing into a manic phase, Kung told MyHeatlhNewsDaily. In such cases, doctors have to consider that the patient could have a bipolar disorder, even if there's a seasonal rhythm to it.

"This is something that the psychiatrists or psychologists need to look for in the medical history," Kung said. "It's important because the patient would require a different set of treatments, and medication during the manic phase. For example, you'd have to switch out the antidepressant medication when the patient goes through mania."

Like depression and bipolar disorder, some patients with SAD are helped by medication and cognitive behavioral therapy . Psychiatrists might also recommend light therapy if the SAD symptoms are mild. During light therapy, patients sit near a specialized artificial light box for a prescribed amount of time, usually during the morning.

"Light therapy and cognitive behavioral therapy can be equally effective at first," said Yael Nillni, a researcher who studies SAD at the University of Vermont.

"However, after the 1-year and 2-year follow-up, we see that cognitive behavioral therapy does a better job of prepping the patient and preventing recurrences of depression during the following winter," she said.

Both Kung and Nillni agreed that SAD, though it may sound almost harmless, can be a serious mental illness and require patience and careful diagnosis by a trained health professional.

"Sometimes we may not realize it is SAD during the first consultation, since the symptoms can overlap with other mood disorders," Kung said.

"That's why it's important to stick with the same psychiatrist for a few visits, in order to give them the opportunity to strip away at the symptoms, get to the right diagnosis, and offer the proper treatment."

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