Why do people with seasonal affective disorder feel like their arms and legs are heavy like lead?

It is called a : Leaden depression.People who suffer from sad have many of the common signs of depression, including sadness, anxiety, irritability, a loss of interest in their usual activities, an inability to concentrate, extreme fatigue and lack of energy, a “leaden” sensation in the limbs, an increased need for sleep, a craving for carbohydrates and weight gain.http://www.prweb.com/releases/2013/12/prweb1144 i am afraid that we do not know exactly why it is that people get thattype of feeling in their limbs.

SAD: Seasonal affective disorder is a type of depression brought on especially in fall and winter when exposure to light is decreased. In some locales it can occur in the summer. A "leaden" feeling is simply part of this depressive syndrome. It may relate to the extreme fatigue which is also part of the syndrome.