Summary: A new study points to cannabis as a possible trigger for schizophrenia in teens.
Psychoactive compound in cannabis may trigger the brain disorder, researchers say.
Scientists believe that schizophrenia, a disorder caused by an imbalance in the brain’s chemical reactions, is triggered by a genetic interaction with environmental factors. A new Tel Aviv University study published in Human Molecular Genetics now points to cannabis as a trigger for schizophrenia.
The research, conducted by Dr. Ran Barzilay and led by Prof. Dani Offen, both of TAU’s Sackler School of Medicine, finds that smoking pot or using cannabis in other ways during adolescence may serve as a catalyst for schizophrenia in individuals already susceptible to the disorder.
“Our research demonstrates that cannabis has a differential risk on susceptible versus non-susceptible individuals,” said Dr. Barzilay, principal investigator of the study. “In other words, young people with a genetic susceptibility to schizophrenia — those who have psychiatric disorders in their families — should bear in mind that they’re playing with fire if they smoke pot during adolescence.”
The research team included Prof. Inna Slutsky and Hadar Segal-Gavish, both of TAU’s Sackler School of Medicine, and Prof. Abraham Weizman of Geha Medical Health Center and Prof. Akira Sawa of Johns Hopkins Medical Center.
Clinical picture of mouse models mimics human adolescence
Researchers exposed mouse models with a genetic susceptibility to schizophrenia — the mutant DISC-1 gene — to THC, the psychoactive compound in cannabis. During a time period similar to that of human adolescence, the susceptible mice were found to be at a far higher risk for lasting brain defects associated with the onset of schizophrenia.
Four categories of mice were used in the experiment: Genetically susceptible and exposed to cannabis; genetically susceptible and not exposed to cannabis; genetically intact and exposed to cannabis; and, finally, genetically intact and not exposed to cannabis. Only the genetically susceptible mice developed behavioral and biochemical brain pathologies related to schizophrenia after being exposed to cannabis, behavioral tests and neurological biochemical analyses revealed.
“The study was conducted on mice but it mimics a clinical picture of ‘first episode’ schizophrenia, which presents during adolescence in proximity to robust cannabis use,” said Dr. Barzilay, a child and adolescent psychiatrist.
The researchers also discovered the mechanism through which the cannabis and the specific gene interact.
“A protective mechanism was observed in the non-susceptible mice,” said Prof. Offen. “This mechanism involves the upregulation of a protective neurotrophic factor, BDNF, in the hippocampus. We showed in the study that if we artificially deliver BDNF to the genetically susceptible mice, they could be protected from the deleterious effect of THC during adolescence.
“This research clearly has implications in terms of public health,” Prof. Offen concluded. “The novel protective mechanism identified in the study may serve as a basis for the future development of compounds capable of attenuating the deleterious effect of cannabis on brain development. However, until that time, it is important that young people at risk for psychiatric disorders (i.e., have psychiatric disorders in their family or have reacted strongly to drugs in the past) should be particularly cautious with cannabis use during adolescence.”
Source: George Hunka – AFTAU
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: Abstract for “BDNF Overexpression Prevents Cognitive Deficit Elicited by Adolescent Cannabis Exposure and Host Susceptibility Interaction” by Hadar Segal-Gavish, Neta Gazit, Yael Barhum, Tali Ben-Zur, Michal Taler, Shay Henry Hornfeld, Irit Gil-Ad, Abraham Weizman, Inna Slutsky, Minae Niwa, Atsushi Kamiya, Akira Sawa, Daniel Offen, and Ran Barzilay in Human Molecular Genetics. Published online April 11 2017 doi:10.1093/hmg/ddx139
BDNF Overexpression Prevents Cognitive Deficit Elicited by Adolescent Cannabis Exposure and Host Susceptibility Interaction
Cannabis abuse in adolescence is associated with increased risk of psychotic disorders. Δ-9-tetrahydrocannabinol (THC) is the primary psychoactive component of cannabis. Disrupted-In-Schizophrenia-1 (DISC1) protein is a driver for major mental illness by influencing neurodevelopmental processes. Here, utilizing a unique mouse model based on host (DISC1) X environment (THC administration) interaction, we aimed at studying the pathobiological basis through which THC exposure elicits psychiatric manifestations. Wild-Type and dominant-negative-DISC1 (DN-DISC1) mice were injected with THC (10 mg/kg) or vehicle for 10 days during mid-adolescence-equivalent period. Behavioral tests were conducted to assess exploratory activity (open field test, light-dark box test) and cognitive function (novel object recognition test). Electrophysiological effect of THC was evaluated using acute hippocampal slices, and hippocampal cannabinoid receptor type 1 and brain-derived neurotrophic factor (BDNF) protein levels were measured. Our results indicate that THC exposure elicits deficits in exploratory activity and recognition memory, together with reduced short-term synaptic facilitation and loss of BDNF surge in the hippocampus of DN-DISC mice, but not in wild-type mice. Over-expression of BDNF in the hippocampus of THC-treated DN-DISC1 mice prevented the impairment in recognition memory. The results of this study imply that induction of BDNF following adolescence THC exposure may serve as a homeostatic response geared to maintain proper cognitive function against exogenous insult. The BDNF surge in response to THC is perturbed in the presence of mutant DISC1, suggesting DISC1 may be a useful probe to identify biological cascades involved in the neurochemical, electrophysiological, and behavioral effects of cannabis related psychiatric manifestations.
“Trends in Fighting and Violence Among Adolescents in the United States: Evidence From the National Survey on Drug Use and Health, 2002–2014” by Christopher P. Salas-Wright, Erik J. Nelson, Michael G. Vaughn, Jennifer M. Reingle Gonzalez, David Córdova in American Journal of Public Health. Published online April 20 2017 doi:10.2105/AJPH.2017.303743