The present invention relates to compositions comprising N,N-dimethyltryptamine, deuterated N,N-dimethyltryptamine and/or partially deuterated N,N-dimethyltryptamine. In particular, the present invention relates to compositions comprising a combination of N,N-dimethyltryptamine and 2% or more by weight of one or more deuterated N,N-dimethyltryptamine compound selected from α,α-dideutero-N,N-dimethyltryptamine and α,α,β,β-tetradeutero-N,N-dimethyltryptamine. Additional and alternative compositions of the present invention comprise a combination of N,N-dimethyltryptamine and 2% or more by weight of one or more partially deuterated N,N-dimethyltryptamine compound selected from α,β,β-trideutero-N,N-dimethyltryptamine, α,β-dideutero-N,N-dimethyltryptamine, and α-deutero-N,N-dimethyltryptamine. Methods of synthesising compositions of the present invention, and methods of use of presently described compositions in treating psychiatric or psychocognitive disorders, such as major depressive disorder, are also provided.