An implantable lead comprising: an elongated member having a distal end, a proximal end, and a longitudinal length; a plurality of electrodes disposed on the distal end of the elongated member ; a plurality of terminals disposed on the proximal end of the elongated member ; a plurality of conductors , each conductor electrically coupling at least one of the electrodes to at least one of the terminals , wherein at least one of the conductors comprises at least one unit , the at least one unit comprising a first conductor segment extending along the elongated member from a beginning point to a first position, a second conductor segment extending along the elongated member from the first position to a second position, and a third conductor segment extending along the elongated member from the second position to an endpoint, wherein the first position is between the second position and the endpoint, and the second position is between the beginning point and the first position; an inner insulator layer disposed along at least a portion of the elongated member , wherein the inner insulator layer is formed of a non-conductive material that is flowable when applied to the conductors to fill in at least some open spaces between portions of at least one of the units ; and an outer insulator layer formed of a non-conductive material and disposed over at least a portion of the inner insulator layer , wherein the outer insulator layer has at least one physical characteristic that is different from the inner insulator layer ; wherein at least one of the inner insulator layer or the outer insulator layer is formed from a doped material or a composite material. an elongated member having a distal end, a proximal end, and a longitudinal length; a plurality of electrodes disposed on the distal end of the elongated member ; a plurality of terminals disposed on the proximal end of the elongated member ; a plurality of conductors , each conductor electrically coupling at least one of the electrodes to at least one of the terminals , wherein at least one of the conductors comprises at least one unit , the at least one unit comprising a first conductor segment extending along the elongated member from a beginning point to a first position, a second conductor segment extending along the elongated member from the first position to a second position, and a third conductor segment extending along the elongated member from the second position to an endpoint, wherein the first position is between the second position and the endpoint, and the second position is between the beginning point and the first position; a first conductor segment extending along the elongated member from a beginning point to a first position, a second conductor segment extending along the elongated member from the first position to a second position, and a third conductor segment extending along the elongated member from the second position to an endpoint, wherein the first position is between the second position and the endpoint, and the second position is between the beginning point and the first position; an inner insulator layer disposed along at least a portion of the elongated member , wherein the inner insulator layer is formed of a non-conductive material that is flowable when applied to the conductors to fill in at least some open spaces between portions of at least one of the units ; and an outer insulator layer formed of a non-conductive material and disposed over at least a portion of the inner insulator layer , wherein the outer insulator layer has at least one physical characteristic that is different from the inner insulator layer ; wherein at least one of the inner insulator layer or the outer insulator layer is formed from a doped material or a composite material. <EOS>