Higher Twist Contributions to the Generalized Gdh Sum Rule

The generalized GDH sum rule has the potential of becoming a show-case of how perturbative QCD and effective low energy hadronic descriptions match at a scale of roughly Q² = 0.5 GeV². Coming from the QCD side the crucial question is the control of higher twist terms which determine down to which Q² a QCD description is sensible. The status of the OPE for the relevant higher twist terms is reviewed and it is extended to include cat-ear terms. Some numerical estimates from lattice QCD are presented and some general properties are discussed. The general conclusion is that higher twist effects are very small, such that the Q²-dependence is dominated by the elastic contribution. This should allow for a smooth connection to low energy models.