Lawrence I. Sank observed that masturbating prone (lying face downward) could be responsible for sexual problems in some men, including anorgasmia and erectile dysfunction, as observed in four men he examined. He coined the term "traumatic masturbatory syndrome" to describe this theory. As of 2007, no follow-up research has been conducted and the idea is not familiar or widely-held within the medical community. Some sources, however, give credence to the idea. One sex therapist condemned masturbation by rubbing against a pillow or mattress and Lipsith et al. suggest that masturbation could play a part in male psychogenic sexual dysfunction (MPSD), citing Sank as their authority. MPSD is a difficulty in reaching orgasm during intercourse, and developing a dependence on masturbation.