Portal vein hypertension

My son has portal vein hypertension which resulted from a clot during his first open heart surgery.  The TIPS procedure was unsuccessful b/c the portal vein was occluded.  During the fall and winter months my son will have bleeding episodes which require blood transfusions, however, little if any bleeding during the summer.  We have central air so I don't think it's temperature related.  We live in Michigan and it is suspected that he has SAD.  Can depression (lack of vitamin D, etc.) cause the pressures in the portal vein to increase thus leading to bleeding?  I know this sounds strange but we really would appreciate any thoughts you might have.
Thanks