Is seasonal affective disorder real or a made up thing. ?

Real: I live in the NorthEast where Seasonal Affective Disorder can be a real problem. SAD symptoms usually occur with change in season (often fall and winter) & can include carbohydrate craving, increased appetite with weight gain, low energy level, irritability, moodiness, sleeping more, heavy feeling in extremities, being overly sensitive to rejection and it can impact relationships.