Understanding Seasonal Depression

Everyone experiences unhappiness, but depression may be diagnosed when symptoms last for two consecutive weeks (or longer) and that are severe enough to interrupt daily life.

Twenty-six million or 46 million: One is the number of American adults living with mental illness and one is the number of Americans living with Type 2 diabetes, one of the fastest growing diseases in the U.S. right now. Would you be surprised that as many as 20 percent of American adults -- that's almost 46 million people -- suffered not from diabetes, but rather from a mental illness during the past year, and as many as 5 percent (that's about 11.5 million people) suffered so severely that their symptoms impaired their normal daily lives [source: Substance Abuse and Mental Health Service Administration]?

Anxiety disorders, eating disorders, impulse control disorders and addiction, mood disorders, personality disorders and psychotic disorders are the most common recognized types of mental health disease in the United States. If we look even closer, a little more than 24 million people are affected specifically by the symptoms of depression, a mood disorder, every year -- roughly the same number of American adults diagnosed with Type 2 diabetes [sources: American Foundation for Suicide Prevention, Centers for Disease Control and Prevention]. Like diabetes, mental illness is a medical condition that is a growing public health problem.

Mood disorders are the most commonly diagnosed mental health condition in the U.S., but can look and feel a bit different from person to person. Some people may have one mild depressive episode in a lifetime, while others may suffer from chronic periods of severe depression. Some may suffer from psychotic symptoms such as delusions or from symptoms of melancholia. Some people may have depressive episodes followed by periods of mania, known as bipolar disease. And even still, some forms of depression may be triggered postpartum, while others may follow a seasonal pattern.

Seasonal depression, also known as seasonal affective disorder or SAD, is a type of major depression, with recurrent depressive episodes triggered by seasonal changes. An estimated 11 million Americans suffer from SAD [source: Marano].

Let's find out more about the symptoms of seasonal affective disorder next.