ABSTRACT
Mismatch negativity (MMN) is an auditory event-related potential indicating auditory sensory memory and information processing. The present study tested the hypothesis that chronic cannabis use is associated with deficient MMN generation. MMN was investigated in age- and gender-matched chronic cannabis users (n = 30) and nonuser controls (n = 30). The cannabis users were divided into two groups according to duration and quantity of cannabis consumption. The MMNs resulting from a pseudorandomized sequence of 2 × 900 auditory stimuli were recorded by 32-channel EEG. The standard stimuli were 1,000 Hz, 80 dB SPL and 90 ms duration. The deviant stimuli differed in duration (50 ms) or frequency (1,200 Hz). There were no significant differences in MMN values between cannabis users and nonuser controls in both deviance conditions. With regard to subgroups, reduced amplitudes of frequency MMN at frontal electrodes were found in long-term (≥8 years of use) and heavy (≥15 joints/week) users compared to short-term and light users. The results indicate that chronic cannabis use may cause a specific impairment of auditory information processing. In particular, duration and quantity of cannabis use could be identified as important factors of deficient MMN generation.
Subject(s)
Contingent Negative Variation/drug effects , Electroencephalography , Evoked Potentials, Auditory/drug effects , Marijuana Abuse , Acoustic Stimulation , Adult , Auditory Cortex/drug effects , Auditory Cortex/physiopathology , Auditory Perception/drug effects , Cognition Disorders/etiology , Cognition Disorders/physiopathology , Dronabinol/pharmacology , Female , Hallucinogens/pharmacology , Humans , Male , Marijuana Abuse/complications , Marijuana Abuse/metabolism , Marijuana Abuse/physiopathology , Memory Disorders/etiology , Memory Disorders/physiopathology , Receptors, Cannabinoid/metabolism , TimeABSTRACT
Chronic cannabis use has been found to be associated with major depression. It is suggested that cannabis use induces changes in neurotransmitter systems involved in the pathogenesis of depressive disorders, particularly in the serotonergic system. The analysis of the loudness dependence of auditory evoked potentials (LDAEP) is a valid non-invasive indicator of central serotonergic activity in animals and humans. In the present study, we investigated the effects of chronic cannabis use on LDAEP in 30 psychiatrically unaffected users compared to 30 non-user controls. Users were required to abstain from cannabis for at least 24 h before testing. Putative depressive symptoms were assessed by using the Beck Depression Inventory (BDI) and the Hamilton Rating Scale for Depression (HAMD-21). LDAEP as well as BDI and HAMD-21 scores did not differ between cannabis users and controls. Moreover, LDAEP neither correlate with duration and quantity of cannabis use nor with psychometric assessments. These results indicate that chronic cannabis use had no influence on the LDAEP in this study sample. It can be suggested that significant alterations in serotonergic systems may rather be related to acute activation of the endogenous cannabinoid system or to cannabis dependence accompanied by manifest depressive symptoms.
