There are many amazing underground creatures. The stars of the underground show are earthworms,__16__ their role in building soil, their importance to gardeners, and the fascination they afford schoolchildren. Earthworms are giants compared with most other soil__17__ . The earthworm’s body is made of__18__ cylinders, which look like many little rings joined together. They are__19__ that chew their way through soil, feeding on plant and animal detritus and on microbes, digesting and thoroughly mixing organic and inorganic components before eliminating it as humus. This__20__breaks complex organic molecules down into simpler forms more suitable for uptake by plants.

        When he moved from South Africa to New York City, Norman Rosenthal, a psychiatrist, noticed he felt more depressed during the cold, short days of the city’s winters than he had in his home country. Years later, he published the first paper to scientifically name the winter blues: Seasonal Affective Disorder (SAD). Subsequent studies have found that the seasonal depression affects those in northern latitudes more and that about 10 percent of SAD sufferers have symptoms in the summertime instead.          The most commonly reported symptoms of winter depression are hypersomnia, the desire to sleep more than usual, as well as an increased appetite and lack of interest in things. According to experts, most people experience symptoms in young adulthood, but SAD can begin at any stage of life. The condition also varies by sex. About three times as many women as men get SAD.

       But why does less daylight make some people clinically depressed? One leading theory is that the change in daylight disrupts our bodies' release of melatonin, a hormone the brain releases every night to promote sleep. As the supply of daylight dwindles in winter, melatonin may wear off later. That means in the morning the body is still in a state of biological night. As for summer SAD, triggers might include the heat and humidity. Instead of feeling lethargic, summer SAD patients more often feel irritable and agitated.

       Experts say a professional diagnosis is a crucial first step toward treatment and self-diagnosis is not suggested. One common treatment is sitting in front of a bright box of light for 30 minutes to signal to the body that it’s time to wake up. But the drawback to light boxes is that they only work on the day that you use them, so you need to use them daily. Another treatment that may have longer lasting benefits is Cognitive Behavioral Therapy (CBT), a form of talk therapy. As negative thinking tends to breed negative emotions, CBT aims to encourage more neutral thoughts. For example, “I hate winter” might be reframed as “winter isn’t my favorite season, but I still find things to enjoy.” Moreover, finding wintertime hobbies may also help. People with SAD often have hobbies that are summer specific, such as growing gardens or beach going. Instead of hibernating under a blanket, people are encouraged to find indoor hobbies, such as knitting, reading, or going to the gym, to boost their mood. Whether using light or talk therapy, there is no reason to not seek mental health treatment, even if symptoms are only present for a few months out of the year.