Amygdala reactivity is inversely related to level of cannabis use in individuals with comorbid cannabis dependence and major depression.
Phan et al. (2008) recently reported that an acute dose of oral THC is associated with a decrease in threat-related amygdala reactivity during a social threat stimulus task. However, to date, those findings have not been replicated, and have not been extended to clinical studies involving smoked rather than oral cannabis. In this study, we hypothesized that level of cannabis smoked by participants in our treatment study would be inversely related to the level of threat-related amygdala reactivity. Subjects were recruited from among participants in our double-blind, placebo-controlled trial of fluoxetine in comorbid youth with cannabis dependence/major depression. The threat-related amygdala reactivity task used by Hariri et al. (2009) was completed during BOLD fMRI scans at study baseline and then again 12 weeks later at the end of the trial. Data are available from six subjects with pre-and post-treatment fMRI data. During the course of the study, five of the six subjects demonstrated a decrease in their level of cannabis use, with a mean decrease of 64%, and those persons all demonstrated an increase in their level of amygdala reactivity. One subject demonstrated an increase in their level of cannabis use (a 79% increase) during the treatment trial, and that person demonstrated a decrease in their level of amygdala reactivity. Thus, a higher level of cannabis use was consistently associated with a lower level of amygdala reactivity across all subjects (matched pairs t = 2.70, df = 5, p < 0.05, two-tailed). These findings are consistent with the reports by Phan et al. (2008) and Hariri et al. (2009) suggesting that cannabinoids have an inhibitory effect on threat-related amygdala reactivity.
Cornelius
Jack R
JR
Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, United States. corneliusjr@upmc.edu
Aizenstein
Howard J
HJ
Hariri
Ahmad R
AR
D000679:Amygdala / Q000187:drug effects* / Q000503:physiopathology; D018687:Antidepressive Agents, Second-Generation / Q000627:therapeutic use; D002188:Cannabis / Q000009:adverse effects*; D015897:Comorbidity; D003866:Depressive Disorder / Q000188:drug therapy / Q000453:epidemiology; D017831:Diagnosis, Dual (Psychiatry); D004311:Double-Blind Method; D005239:Fear / Q000187:drug effects*; D005260:Female; D005473:Fluoxetine / Q000627:therapeutic use; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology / Q000503:physiopathology*; D012919:Social Behavior; D055815:Young Adult
D018687:Antidepressive Agents, Second-Generation; D005473:Fluoxetine