Patients with posttraumatic stress disorder have more cannabinoid receptors and fewer endocannabinoids in plasma than people without the disorder.

The consolidation of emotionally aversive memories that underlies the development of posttraumatic stress disorder (PTSD) occurs via a synergistic interaction between stress-induced cortisol and norepinephrine inputs into the amygdala, which are modulated by endocannabinoid signaling. These researchers examined availability of cannabinoid 1 (CB₁) receptors during resting positron emission tomography in 25 untreated PTSD patients, 12 non-PTSD trauma controls, and 23 healthy controls. Cortisol and other possible biomarkers were also measured.

Compared with healthy and trauma controls, PTSD patients had significantly more CB₁receptors (20% and 14% higher, respectively) both overall and in CB-rich and fear-relevant hippocampal, amygdala, and corticostriatal areas. PTSD was associated with lower plasma levels of the endocannabinoid anandamide (53% and 58% lower). Both effects were more pronounced in women. Cortisol levels were lower in PTSD patients and trauma controls than in healthy controls. Use of all three biomarkers enabled accurate classification of 85% of PTSD cases.

Comment: This study is the first to document abnormalities in cannabinoid signaling in PTSD, with lower endocannabinoid levels likely driving the greater CB₁ receptor availability. The findings are consistent with reports of frequent self-medication with cannabis in PTSD patients. The authors warn against cannabis self-medication; note that chronic use of CB agonists down-regulates CB receptors, thus producing a depressive phenotype over time and aggravating substance dependence; and suggest that medications blocking anandamide degradation or uptake are much more likely to restore CB₁ system integrity. Cannabis self-medication in anxious patients might provide short-term relief, but is likely to result in problems similar to those seen with overuse of benzodiazepines to treat anxiety.

Source:  Journal Watch Psychiatry