Feynman-Kac formulas are well-known to provide a connection between the spin boson model, describing a spin linearly coupled to a bosonic quantum field, and a continuous one-dimensional Ising model. If the spin boson model is infrared-divergent, i.e., if the bosons are massless, then the pair interaction of the Ising model decays slowly. We discuss how long range order of the Ising correlation functions then implies absence of ground states for the spin boson model. Results implying long range order at large spin-field coupling are also presented. This talk is based on joint work with Volker Betz, Mino Kraft and Steffen Polzer.