In synesthesia, a stimulus evokes sensory experiences in more than one sensory modality. Although synesthesia is a well-known condition, there is little understanding of how it comes about in the brain. Two theories are currently debated upon, the disinhibition-unmasking hypothesis and the hyperconnectivity hypothesis. Previous research has been conducted using various methods (e.g., associative learning & pharmacological induction) to induce synesthesia in non-synesthetes. This systematic review examined if synesthesia can be modified by posthypnotic suggestion with an aim to attain a clearer understanding of its neural underpinnings in regard to the two theories. Successful manipulation of synesthetic experiences through posthypnotic suggestion would strengthen the disinhibition-unmasking hypothesis. All studies on induction of synesthesia in this review indicate that it is possible to induce synesthetic-like experiences in non-synesthetes. Furthermore, one case study showed that disruption of synesthesia was also possible in one synesthete. Nonetheless, there is an agreement that these synesthetic experiences are not exactly comparable to those found in natural synesthesia. Studies used in this review all have a common limitation concerning the small sample size. Additionally, these few studies are currently some of the only ones thatexamine this very issue. Future research should aim at reproducing the current studies to see if the effect seen is replicable. It would also be beneficial to establish a common methodology for these experiments so that there can be fewer confounding variables.