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Bad weather can really affect your mood, (can't) it? Most of us get depressed at some point (during) the winter and we can not wait for spring to come. For some people (however) those dark cold winter days can cause real medical problems.
doctors have (produced) acondition which is (known) as SAD. and it can be a big problem in countries. SAD sufferers find it difficult to (concentrate) often feel depressed or anxious their behavior affects the people around them.
Bright light affects the chemistry of the brain although scientists do not understand (exactly) how. the first is to travel to a country that has a warm (climate) with bright, sunny winters. the second is to use (artificial) light.