chronic cannabis users: a model for negative symptoms in schizophrenia

Conditions: Chronic Cannabis Users; Healthy Subjects

Summary: the aim of the current study is set out to find a human model for negative symptoms based on clinical observation that chronic cannabis users express negative symptoms and characterize by the same neurocognitive and electrophysiology characteristics like patient suffer from schizophrenia. towards that end the first part of the study is set out to explore weather chronic cannabis user's express negative symptoms similar to patient suffer from schizophrenia. the second part of the study will explore the neurocognitive and electrophysiology characteristics of those cannabis users that express negative symptoms. this data will be compared to parallel data of schizophrenia patients with predominantly negative symptom. several lines of biological and genetic evidence support the cannabinoid hypothesis for schizophrenia. particularly, it is most significant clinically that the possible involvement of the cannabinoid system in the neural basis for the negative symptoms. this hypothesis based on clinical findings that chronic cannabis use causes a combination of symptoms including apathy, avolition, lack of interest, passivity, and cognitive impairments, the so-called "amotivational syndrome," which resembles the core negative symptoms of schizophrenia in behavioral level as well as the brain level. both are associated with the functions or integrity of the frontal lobe due to its role in creating self-directed behaviors, deficits in which may underlie alogia, anhedonia, and flat affect. despite the aforementioned similarities, to date, there is no documentation for such a relationship. recognition that chronic cannabis users share the same or similar constellation of symptoms and similar neurocognitive and electrophysiology characteristics could provide a key to develop a human model for negative symptoms and an essential tool to comprehensive understanding of the etiology of negative symptoms and development of an innovative therapy. the investigators hypothesize that chronic cannabis users would express the same constellation of behaviors as negative symptoms of schizophrenia; as well as similar neurocognitive and electrophysiology characteristics


Eligibility criteria:
inclusion criteria for both groups: 1. healthy men and women 2. ages 20-65 3. give informed consent for participation in the study. inclusion criteria for the control: -used cannabis maximum 50 times in their lives, and no more than once during the past year. inclusion criteria for the experimental: -use of cannabis for at least 2 years and in the last 6 months for at least 4 days a week. (-after minimum 12 hours of abstinence (in order to eliminate acute cannabis effects, minimize the withdrawal effect while retaining neurophysiological effects from altered cb1 activity). exclusion criteria for both groups: (to prevent meg artifacts by non relevant electric interference or brain conditions) * history of epilepsy, seizure, or hot spasm, sever head injuries. * history of metal in the head (outside the mouth space). * history of surgery including metal implant or history of metal particles in the eye, pacemaker, or any other medical pump. * history of migraines. * history of drug or alcohol abuse during the last year. inability to achieve satisfying level of communication with the subject control group (healthy subjects) * history of psychiatric diagnosis * drug or alcohol addiction in the year prior to the study * history of epilepsy, seizure, or hot spasm. * history of head injuries. * history of metal in the head (outside the mouth space). * history of surgery including metal implant or history of metal particles in the eye, pacemaker, or any other medical pump. * history of migraines.

Keywords: chronic cannabis users negative symptoms cognitive electrophysiology functions