1. Primary Raynaud syndrome is by far the more common type and has no known cause, but contributing factors include cold weather and emotional stress. It is estimated to occur in about 5 to 10 percent of nonsmokers and is much more common in women than men.

  2. Secondary Raynaud syndrome is the result of a known underlying condition, such as connective tissue disorders (e.g., scleroderma or lupus), nervous system diseases or certain occupationally related disabilities.