2.1. Subjects
Six cannabis users and 7 control subjects were recruited at the IMIM-Hospital del Mar Research Institute (Barcelona, Spain). The study was reviewed and approved by the local institutional ethics committee (CEIC-PSMAR). All subjects provided their written informed consent after the study and procedures were explained to them in full. All the subjects, of either sex, were between 18 and 40 years old, and the cannabis users consumed 5 or more cannabis cigarettes per week. Subjects were instructed to abstain from cannabis use for at least 12 h before testing. The subjects were excluded if they fulfilled any of the following criteria: (1) comply with the criteria for any severe mental disorder according to DSM-V; (2) any history of severe congenital, medical or neurological illness; (3) a history of severe mental illness among first degree relatives; (4) consumption of other drugs of abuse except alcohol and tobacco; and (5) present any medical condition with nasal repercussions (rhinitis or bleeding). The consumption of cannabis was verified by testing for tetrahidrocannabinol (THC) metabolites in urine (Instant-View, Multipanel 10 Test Drug Screen: Alfa Scientific Designs, USA). The exclusion criteria were verified using the Hamilton Depression Rating Scale (HDRS-17), the individual’s clinical history and a diagnostic interview according to DSM-V criteria (SCID). Furthermore, a Neurological Evaluation Scale was used to evaluate neurological soft signs (NSS (Buchanan et al., 1989) and the Global Assessment of Functioning scale (GAF) was used to measure the level of functionality (Endicott et al., 1976).