This invention provides methods of treatment using retro-inverso peptides derived from interleukin-6 (IL-6) having between 15 and about 40 amino acids, and including the sequence that is retro-inverso with respect to SEQ ID NO: 1, i.e. wherein said peptide comprises the sequence D-Glu-D-Ala-D-Met-D-Lys-D-Pro-D-Leu-D-Asn-D-Leu-D-Asn-D-Asn-D-Glu-D-Ala-D-Leu-D-Ala-D-Glu. The peptides of the invention have the same activity as native IL-6 and also have neurotrophic activity. The peptides of the invention are also less susceptible to proteolytic degradation in vivo because of their D-amino acid linkage.