Biological aging can be quantified at the individual cell level by measuring telomere length in peripheral immune cells (leukocytes). Telomeres are located at the end of each chromosome and protect the genetic material during cell division. Telomerase is an enzyme that can lengthen telomeres, and have in this way a protective function against accelerated cellular aging. Variations in these bodily processes have been associated with psychiatric manifestations such as anxiety and depression. In the current study the participant´s telomere length and telomerase activity will be assessed at three occasion. a) Twice before treatment initiation (9 weeks apart), and b) directly after treatment termination.