Psychotic-Like Experiences and Concurrent Substance Use Among People Who Use New Psychoactive Substances.

New psychoactive substances (NPS) are a group of substances that mimic established drugs, e.g., cannabinoids, stimulants, and opioids. NPS use has been associated with psychotic-like experiences, but current research is limited. This study focused on NPS use and psychotic-like experiences in persons attending substance use services in South-West Finland. The primary aim was to evaluate if NPS use associates with psychotic-like experiences, and if the association is independent of comorbid psychotic illness. As a secondary aim, this study evaluated concurrent substance use among people who use NPS. The study was based on a voluntary and anonymous survey administered on-site for people attending substance use services. The survey was conducted in 17 substance use service centers in South-West Finland in 2019, totaling 219 respondents. Information on substance use, service use due to psychotic episodes, and comorbid psychotic illness was collected. A validated PROD questionnaire was used for information on psychotic-like experiences. In all, 17% of 219 participants ( = 38) reported NPS use. After adjustments with comorbid psychotic illness, age, and gender, NPS use associated with PROD-screen positivity, i.e., reporting at least three psychotic-like symptoms. NPS use also associated with service use due to substance-induced psychotic episodes, and extensive use of several substances. In this study, NPS use associated with psychotic-like experiences independently of comorbid psychotic illness. However, as NPS use is also associated with heavy use of several substances, this study implicates concurrent substance use as a confounding factor when studying NPS use, which should be considered in future research.