Use of particular substituted heterocycle fused gamma-carboline compounds as pharmaceuticals and pharmaceutical compositions comprising them for the treatment of one or more disorders involving the 5-HT2A, SERT and/or dopamine D2 pathways are disclosed. In addition, the compounds may be combined with other therapeutic agents for the treatment of one or more sleep disorders, depression, psychosis, dyskinesias, and/or Parkinsons disease or any combinations.